Tesis: "TP Food Processing and Manufacture 368-456"

1

Kantas, Yesim. "Effect Of Ultrasound On Drying Rate Of Selected Produce". Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/3/12608349/index.pdf.

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The objective of this study was to discover the effect of high power direct contact ultrasound on drying rates of apple, celery root, carrot and potato. For this purpose ultrasonic generator with 24 kHz frequency was used and amplitude and pulse mode values were chosen as 40%, 70%, 100%, and 0.4, 0.7, 1.0, respectively. The temperature of drying air was 30°
C, 40°
C and 50°
C and the velocity was kept at 3.9 m/s. The samples used were 13.5 mm in diameter with 5.0 mm thickness. It is found that ultrasound assisted drying increased the drying rate for the selected produce at all the drying conditions used the degree of which depended on the structural properties of samples. Accordingly, the most suitable drying conditions were found to be amplitude 100%, pulse mode 1.0 and 30°
C for celery root, amplitude 100%, pulse mode 1.0 and 30°
C for apple, amplitude 70%, pulse mode 1.0 and 50°
C for carrot and amplitude 70%, pulse mode 0.7 and 50°
C for potato. Data obtained were treated with respect to some mathematical models that describe the drying kinetics of samples. In this respect, Page and Modified Page models were the best to represent the drying rates in all cases. Further, the results showed that the effect of ultrasound on drying rate increased in the order of apple>
celery root>
carrot>
potato. That order can be attributed to the structure and composition where presence of air pockets has enhancing and sugar and starch have reducing effects.

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2

Seyhun, Nadide. "Modeling Of Tempering Of Frozen Potato Puree By Microwave, Infrared Assisted Microwave And Ohmic Heating Methods". Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609666/index.pdf.

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The main purpose of this thesis is to develop a model that can predict the temperature profile inside a frozen food sample during microwave tempering and infrared assisted microwave tempering processes. Another goal of the study is to compare the tempering time of frozen foods by using microwave, infrared assisted microwave, and ohmic heating methods. Frozen potato puree was used as the food sample for all studies. Three different microwave power levels (30%, 40%, and 50%) were used for microwave tempering studies. Three different microwave power levels (30%, 40%, and 50%) and three different infrared power levels (10%, 20%, and 30%) were combined for infrared assisted microwave tempering. As a control, tempering was done by keeping the sample at 4°
C. The increase in microwave power level and infrared power level reduced tempering time in infrared assisted microwave tempering. For the ohmic tempering studies, three different frequencies (10 kHz, 20 kHz, and 30 kHz) and three different salt contents (0.50%, 0.75%, and 1.00%) were used. The increase in frequency of ohmic heating and salt content also decreased tempering times. Microwave tempering and infrared assisted microwave tempering of frozen foods were simulated by using finite difference method. For this purpose, the change in heat capacity and the dielectric properties of frozen potato puree with respect to time were measured. The temperature distribution inside the sample was modeled, and the predicted results were compared with experimental results. The predicted temperatures showed good agreement with the experimental data (r2 >
0.985). It was possible to decrease tempering times by about 75%, 90%, and 95% using ohmic, microwave, and infrared assisted microwave tempering methods, respectively as compared to control.

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3

Nantiyakul, Nantaprapa. "Processing rice bran to yield added-value oil based extracts". Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/12669/.

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Rice bran, a by-product from rice milling, is an excellent source of natural antioxidants. Lipids in rice bran appear as small spherical droplets called oil bodies. This work attempted to recover the oil bodies from rice bran (fresh, stored and heat-treated) and to determine their chemical, biochemical and physical properties ex vivo. As revealed by transmission electron microscopy, oil bodies were observed mainly in the sub-aleurone and aleurone layer of brown rice. Oil bodies were successfully recovered from rice bran and were enriched in tocochromanols and oryzanol (656 - 1,006 mg/kg lipid and 8,880 - 9,692 mg/kg lipid respectively). Further washing to remove extraneous protein and non-associated compounds, effective lipid concentration increased while protein concentration decreased. The washed oil body preparation contained approximately 35 - 68 % tocochromanols and 60 - 62 % oryzanol of the parent rice bran oil. Therefore, the majority of tocochromanols and oryzanol molecules appeared to be intrinsically associated with rice bran oil bodies ex vivo. Fatty acid composition of rice bran oil bodies was similar to that of parent rice bran. SDS-PAGE of proteins present in differentially washed oil body preparations revealed similar protein profiles; however, there was a relative enrichment of the bands at 16 - 18 kDa (typical molecular weight of oleosins). Rice bran oil bodies possessed negatively charged surface (-30 mV) at neutral pH. As the pH of the oil body suspension was lowered to the pH near pI (about pH 4 - 5), zeta potential of the oil bodies approached zero and the suspension had the least physical stability; aggregation and the least relative turbidity. The biochemical instability of rice occurs immediately after milling, which leads to the limited use of rice bran for human consumption. Free fatty acids and lipid hydroperoxides in rice bran and corresponding oil bodies increased significantly (P<0.05) during storage. Oil bodies recovered from stored rice bran aggregated and coalesced. 41% of tocochromanols in the oil bodies had decomposed while the concentration of oryzanol was relatively stable during the storage. Rice bran heat treatments (pan roasting and extrusion) caused the coalescence of oil bodies in vivo and the instability of an oil body suspension ex vivo. The main findings of this study were that rice bran oil bodies were enriched in phytochemicals including tocochromanols and oryzanol and were resistant to oxidation providing that the oil bodies were still intact. The oil bodies could delay the onset of lipid oxidation of stored lipids inside the oil bodies. This may be explained by the physical barrier of surface membrane protein (oleosin) against pro-oxidants and the intrinsic association between the oil bodies and phytochemicals in rice bran.

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4

Mohamad, Nizaha Juhaida. "Dark chocolate : understanding the impact of limonene on the crystallization properties and application of green leaf lipid extract as a flow enhancer". Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/42925/.

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Dark chocolate as the main subject matter in this study was investigated for physical changes when formulated with two different lipids based ingredients impacting on the chocolate flow properties. The first ingredient was limonene, known to reduce viscosity when substituting a small fraction of the cocoa butter and to affect cocoa butter crystal morphology, but without knowledge of the impact on bloom formation. The second lipid ingredient was a polar lipid extract from green leaf tissue hypothesised to show functionality as a flow aid, potentially enabling the replacement of currently applied commercial surfactants in chocolate. The driver for this part of the PhD study was to uncover alternatives for the commercial surfactant polyglycerol polyricinoleate (PGPR) which has a negative consumer image. This study was also carried out to devise an opportunity for functionalisation of green tissue waste, although in this first investigation, fresh spinach was used as the raw tissue material. As DGDG was claimed to be the polar lipid compound that caused the low viscosity reduction of dark chocolate by oat lipids, DGDG as well as MGDG are also available abundantly in spinach. The limonene work was using the techniques of whiteness index (WI) to detect bloom, X-ray diffraction (XRD) for crystal identification and differential scanning calorimetry (DSC) for the melting behaviour. Limonene significantly influenced the cocoa butter crystal transformation rate in chocolate which further promoted the development of clearly visible bloom. Nevertheless, limonene may still commercially can be applied in chocolate filling or white chocolate bars where bloom formation is not visible. Polar green leaf tissue lipids were extracted from both spinach leaf and spinach chloroplast due to their difference in composition. Based on compositional analysis of the lipids and their fatty acids by thin layer chromatography (TLC) and gas chromatography (GC), respectively, it was confirmed that leaf contained higher proportion of phospholipids compared to chloroplast, which was highly concentrated with glycolipids. The surface active nature of both lipid extracts was confirmed by interfacial tension measurements at the oil/water interface. Leaf and chloroplast lipid showed a comparable surface activity and demonstrated to be more surface active than lecithin and PGPR. Before applying as flow aid into a complex chocolate formulation, sugar/oil suspensions with added surfactant were rheologically analysed. The performance of the two green tissue extracts was compared to the commercially applied lecithin and PGPR in a concentration range of 0.1 % to 0.7 % based on total suspension containing between 40 and 50 % sugar by weight. Both spinach leaf and chloroplast lipids showed a comparable result in influencing the rheological properties of chocolate model. Therefore, due to the higher lipid recovery from leaf compared to chloroplast as the basic of parent leaf, application in chocolate to verify the results obtained for the model system was executed only for leaf lipid extract. Based on the model suspension results addition at 0.3 and 0.6% on chocolate by weight was considered. Spinach leaf lipid decreased the viscosity of chocolate to value lower than lecithin and PGPR added at the both levels. Yield value measured at 5 s-1 was also reduced; at both levels of addition providing an advantage over lecithin which was shown and is known to increase yield stress at higher level of addition. On the other hand, the yield (5 s-1) lowering capacity was less pronounced than PGPR whereas it was found to be effective based on the model chocolate system. The present results show promise for green leaf tissue lipid to be applied as surfactant in chocolate or fat based food suspension although further research is required to develop the full potential of this natural surfactant system.

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5

Santhanam, Menon Abhay. "Effects of blanching and drying on the production of polyphenols rich cocoa beans and product quality". Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/43219/.

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The high potential of health beneficial polyphenols and antioxidants in cocoa beans has been a major topic for research in recent years. The large-scale application of cocoa beans for health beneficial compounds is relatively unexplored and it needs to be widely utilized by pharmaceutical and nutraceutical industries. Processing methods such as fermentation and drying are major deterrents for recovering high polyphenols in cocoa beans. Hence, it was the intention of this work to introduce the application of hot water blanching pre-treatment and various drying methods for producing polyphenols rich cocoa beans by using unfermented beans. The studies incorporated the application of various drying methods such as oven, adsorption, vacuum, freeze and sun drying methods on cocoa beans. The studies compared the ability of these drying methods to preserve the bioactive capacities namely, total polyphenolic contents and antioxidants activity after hot water blanching. The potential of adsorption, vacuum and freeze drying methods for recovering high polyphenols content are useful in comparing it with the conventional cocoa drying methods such as oven and sun drying methods. For the studies on oven drying of cocoa beans, the drying parameters (T= 60°C, 70°C and 80°C) used were similar to the conventional hot air drying parameters used in industries. The total polyphenolic contents of fermented cocoa beans dried at 70°C was found to be the highest. The polyphenols degradation kinetics for oven drying method of cocoa beans was determined using first-order reaction kinetics model based on various drying temperatures and durations of drying. The studies on drying kinetics of fresh cocoa beans dried using oven, vacuum, adsorption and sun drying methods were successfully analysed. It was found that adsorption drying and vacuum drying methods dried cocoa beans faster than oven and sun drying methods. Two respective falling rate periods were recorded by adsorption and vacuum drying. The effective diffusivities were determined and were found to be in accordance to that of published literatures. Hot water blanching pre-treatment were performed for fresh and fermented cocoa beans (whole beans and half cut). Blanching pre-treatment method was found to show significantly higher total polyphenolic contents when compared with unblanched cocoa samples. The optimal blanching parameter (90°C for 5 min) obtained for fresh beans were subsequently used for experiments involving fresh cocoa beans. The total polyphenolic contents and antioxidant activity of blanched and unblanched cocoa beans were analysed. Results showed that both adsorption and vacuum drying methods showed high recovery of polyphenolic compounds and antioxidants on comparison with freeze dried cocoa samples, which was used as a benchmark in quality analysis of food products. High polyphenols contents were achieved after the blanching and drying treatments and were noted to be significantly higher on comparison with published literatures. Sensory analysis of both blanched and unblanched cocoa beans were analysed after drying using various drying methods. The results for unfermented cocoa beans showed high astringency flavour attributes which further confirmed the high contents of polyphenols in cocoa beans. The cocoa and acidic flavour attributes were recorded to be less owing to the unfermented nature of cocoa beans. The results obtained provides a gateway towards the use of advanced drying technology in cocoa industry. The potential of blanching pre-treatment to mediate high recovery of cocoa polyphenols after drying has been proven through this work. The processing methods used in the current study can be implemented in on-farm cocoa processing, making it a more sustainable farming option.

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6

Moirangthem, Kamaljit. "Overcoming challenges for the biorefineries of the future". Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/48138/.

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Non-food lignocellulosic biomass is the most abundantly available raw material. Utilising it for biorefinery purposes not only circumnavigates the food vs fuel debate, but is also important for a complete move to a fossil fuel free society. Some of the major challenges in using lignocellulosic feedstock includes its recalcitrance, potential shortage for year-round mono feedstock supply and economic viability with current technology. The first part of this thesis explores the potential of overcoming recalcitrance of wheat straw by exploiting new wheat back cross (BC1) plants, which were developed at Nottingham, using introgression of genes from wild relatives, with the aim to improve wheat genetic variation. The straw from a subset of 128 BC1 were screened for sugar content and saccharification efficiency. Plants showed wide compositional and structural differences, reflecting a high degree of genetic diversity. The digestibility of the stem tissue was assessed following acid hydrothermal pre-treatment and a significant variation was detected. This demonstrated that this approach to wheat breeding was successful in introducing a wide range of phenotypic, compositional and structural changes and digestibility into the wheat straw. The second part of the thesis aimed to address the potential bottle neck in mono-feedstock availability in a biorefinery, as most lignocellulosic feedstocks are likely to be seasonal. One way to overcome this may be by utilising a mixed feedstock to maintain a year-round supply. This study reports the impact of mixing three of the UK’s most important feedstocks- wheat straw, willow and Miscanthus on two major performance indicators - sugar yield and fermentation inhibitor production. A hot water pre-treatment regime of 200°C for 5 minutes was applied to each feedstock individually and to 1:1 (w/w) mixes and the predicted sugar yield in the mixes was compared to the observed values. All the mixes resulted in improved sugar yields with willow + Miscanthus and wheat + willow showing a statistically significant improvement over predicted values. Inhibitor production during the pre-treatment and its impact on yeast metabolism and growth were also compared and no adverse impacts of mixing observed. The use of mixed feedstocks in a hot water based commercial production of biofuels is unlikely to have any adverse effects on productivity and may indeed prove beneficial. The final part of the thesis, explores the potential of combining extraction of a high value product (anthocyanin) from black rice - Chakhao poireiton straw, followed by use of the residual straw for saccharification for an economical biorefinery. The anthocyanin content of black rice straw, as determined by standard methanol extraction, was 62.8±4.2 mg/100g. Aqueous microwave treatment at 90°C for 5 minutes extracted 85.8% of this anthocyanin and importantly the extract then displayed higher antioxidant capacity compared to methanol extracts. Extracts showed negligible cytotoxicity, or induction of apoptosis, on Jurkat cell lines even at high concentrations (200-800μg/ml). The straw residue after anthocyanin extraction showed a glucose digestibility of 49.67±1.4% after a subsequent pre-treatment at 200 °C for 5 minutes. This study demonstrates the potential to develop a combined biorefinery process for anthocyanin and second-generation sugars using black rice straw as the feedstock.

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7

Parin, Harika. "Effect Of Pretreatment And Air Temperature On The Drying Rate, Rehydration Capacity And Color Of Artichoke". Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605458/index.pdf.

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In this study, cleaned artichoke hearts belonging to three different ages were dried under constant external conditions at 50, 60 and 70°
C using an air inlet velocity of 8.1 m/s. The sample to be dried was pretreated either by keeping it in distilled water or 1% (w/v) ascorbic acid or sodium bisulfite solutions for 30 minutes at the corresponding drying temperatures. Further, for comparison, the use of citric acid solution, increasing the concentrations of the solutions, reducing the pretreatment time, effect of degree of trimming and halving the samples were investigated. The experimental drying rate data were treated to estimate the effective diffusivities and the effect of temperature together with the activation energy according to an Arrhenius type relation. For the product quality, rehydration capacity of the dried samples in water at 20°
C as well as their color were determined. As expected, the rate results indicated an increase in the drying rate hence the effective diffusivity with temperature for the distilled water and ascorbic acid pretreated samples. However, a reduction in the rate at the high drying temperature when sodium bisulfite solution used was attributed to the clogging of the pores by the precipitated solid due to rapid evaporation at the surface. Similarly, rehydration capacity and color of the water treated samples were enhanced with temperature where with the solution treated ones a reverse effect was observed. It is also found that the rehydration data could be well represented by Peleg equation. Further, when citric acid solution was used for pretreatment, the results were quite identical to those of ascorbic acid. Also, increasing the ascorbic acid concentration to 2% (w/v) improved color whereas decreasing the dipping time increased discoloration. Finally, as an important parameter, the degree of trimming of the hearts proved to be highly effective on the rate and the other studied parameters as well as the post harvest and storage time.

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8

Ozkoc, Semin Ozge. "Investigation Of Quality And Staling Of Breads With Different Gum Formulations Baked In Different Ovens". Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609678/index.pdf.

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The objective of this study was to determine the effects of different gums and their combination on quality and staling of breads baked in different ovens. In the first part of the study, the effects of gums (xanthan, guar, k-carrageenan, hydroxypropyl methylcellulose, locust bean gum and their blends) on quality of breads baked in infrared-microwave combination and conventional ovens were investigated. In addition, macro and micro-structure, dielectric and thermal properties and acrylamide content of breads were studied. Xanthan-guar blend addition improved bread quality with increasing specific volume and porosity values and decreasing hardness values of samples. More homogeneous closed-cell structure for conventionally baked control breads and channel formed cell structure for breads baked in infraredmicrowave combination oven were observed. Dielectric properties of breads were found to be a function of gum type. No acrylamide was formed in microwave baked breads. Breads baked in infrared-microwave combination oven had similar acrylamide content with conventionally baked ones. The second part of the study focused on staling. The hardness, retrogradation enthalpy, set back viscosity, FTIR outputs and crystallinity values of microwave-baked samples were found to be the highest. Infraredmicrowave combination heating made it possible to produce breads with similar staling degrees as conventionally baked ones and reduced the conventional baking time of breads by about 39%. Addition of xanthan-guar blend decreased hardness, retrogradation enthalpy and crystallinity values of breads. According to hardness data, in the presence of xanthan-guar blend staling of breads baked in all types of ovens was delayed for 1 day.

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9

Sevimli, Melike Kadriye. "Optimization Of Processing Conditions During Halogen Lamp-microwave Baking Of Cakes". Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/12605326/index.pdf.

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The main objective of this study was to optimize processing conditions during halogen lamp-microwave combination baking of cake by using Response Surface Methodology. It was also aimed to compare quality of products baked in microwave-halogen lamp combination oven, halogen lamp oven, microwave oven and conventional oven. In the first part of the study, as independent variables, baking time for conventional oven
microwave power and baking time for microwave oven
halogen lamp power and baking time for halogen lamp oven and microwave power, halogen lamp power and baking time for halogen lamp-microwave combination oven were used. Weight loss, specific volume, firmness and color of the cakes were measured during the study. Cakes baked in conventional oven at 175°
C for 24 minutes were determined as the control cakes. Weight loss of cakes increased with increasing independent variables for all oven types. Specific volume and firmness of cakes increased with increasing microwave power, but decreased with upper halogen lamp power. Color formation was achieved in the combination baking but not as much as in the conventional baking. Response Surface Methodology was used to optimize the baking conditions in the second part of the study. Upper and lower halogen lamp powers, microwave power and baking time were used as independent variables. Optimum processing conditions were found as 60% for upper halogen lamp power, 70% for lower halogen lamp power, 30% for microwave power and 5 minutes for baking time. Cakes baked at optimum baking conditions had comparable quality with conventionally baked ones, except color. In short, by the usage of halogen lamp-microwave combination oven it was possible to obtain high quality cakes by reducing of conventional baking time about 79%.

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10

Renshaw, Ryan C. "New insights into RF and microwave drying of foods". Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/43232/.

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This work reports a fundamental study of the science and economics of microwave and RF drying of foods, addressing current knowledge gaps and introducing new techniques to aid the development of new microwave and RF drying processes. The present study has discovered that a correlation exists between the points of inflection of the moisture dependant dielectric properties and the moisture dependant water activity. Hence the moisture dependant dielectric properties are governed by the state of the water as defined by the sorption isotherms. Water activity equations were mathematically modified in this study to successfully describe moisture dependant dielectric properties. This is a valuable contribution to science as there are currently no recognised standard equations for describing the moisture dependence of dielectric properties. These new proposed equations are of great value as they can be used in microwave drying models. This will enable engineers to optimise microwave and RF processes, leading to a reduction in the trial and error approach that currently prevails in industry. Improved optimisation may ultimately lead to more successful microwave and RF applications. It is extremely important to be able to monitor key parameters such as porosity, oil and water content, when introducing a new food processing technique. To this end, a new and novel technique for quantifying the porosity of thin irregularly shaped food has been established. This can be used as a diagnostic tool to assess and optimise processing changes such as the introduction of new microwave or RF drying processes. A good understanding of how RF/MW processes affects porosity can be used to optimise the drying process, leading to a greater probability of success. Sorption isotherm measurements carried out in this study showed that the gelatinisation of starch in potato has a negligible effect on the isosteric heat of sorption. This is important for drying applications, as the isosteric heat of sorption is very significant compared to the latent heat at low moisture contents. Dielectric properties were measured for potato crisps, biscuits, and pasta particulate at 915MHz, and were used to gain new insights into moisture levelling behaviour through analytical analysis. Contrary to common belief, it was found that moisture levelling can be more effective below the critical moisture content, at lower moisture contents. Although moisture levelling limits the variability of the final moisture content, it was found that fine control of the final moisture content can only be achieved by minimising variation in electric field exposure. Feasibility studies of microwave applications showed that finish drying microwave applications were far more practical and cost effective compared to applications that have to remove large quantities of water. Dry food is generally quite thin so that it is eatable, or for rehydration purposes. As a consequence conventional food drying processes tend to be sufficiently energy efficient so that even microwave and RF finish drying processes are comparatively expensive with respect to energy usage. Hence, microwave and RF food drying must be justified by improvements in quality.

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11

Akdeniz, Neslihan. "Effects Of Different Batter Formulations On Quality Of Deep-fat Fried Carrot Slices". Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605202/index.pdf.

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The main objective of the study was to evaluate the effects of starch and gum types on product quality of deep-fat fried carrot slices. It was also aimed to evaluate the applicability of image processing for determination of oil uptake. In the first part of the study, carrot slices were dipped into batters containing three different concentrations of dextrin or pre-gelatinized tapioca starch and fried for 2, 3, and 4 minutes at 170±
2 oC. Coating pick-up of batter formulations and moisture content, oil content, frying yield, bulk density, porosity, texture and color of fried slices were evaluated. In the second part of the study, the effects of different gum types (HPMC, xanthan gum, guar gum, guar-xanthan gum combination) on quality attributes were studied. No starch or gum added coating formulation was used as the control. Finally, images of carrot and batter sections of the fried samples were obtained using digital camera and area fractions of oil droplets were determined using image processing. Acceptable product quality was obtained at higher concentrations of pre-gelatinized tapioca starch. On the other hand, increasing dextrin concentrations had an adverse affect on the product quality. As a result of the study, guar-xanthan gum combination has been found as the most effective additive on the batter performance. This additive provided the highest moisture content, lowest oil content, highest volume and lightest color to the product after frying. The porous and crunchy structure obtained using this combination was at the acceptable level for deep-fat fried products. Determination of area fraction of oil droplets on carrot and batter surfaces of fried samples using image processing was correlated with the oil content of fried product at initial stages of frying. The correlation coefficient between moisture content and frying yield was found as 0.90. A correlation was also determined between oil content and moisture content (r= -0.88).

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12

Gurgen, Emre. "Pea Protein Isolate Production". Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/3/12606434/index.pdf.

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Pea seeds were tempered at moisture contents of 12.0&
#61617
0.1, 13.0&
#61617
0.1, 14.0&
#61617
0.1 and 15.0&
#61617
0.3%. The seeds with different moisture contents were then milled and fractioned according to the particle size of 53, 106, 212, 425 and 850 &
#956
m. Tempering the pea seeds (12.0&
#61617
0.1, 13.0&
#61617
0.1, 14.0&
#61617
0.1 and 15.0&
#61617
0.3%) did not significantly affect the mass and protein fraction in comparison with the pea seeds that are not tempered (11.45&
#61617
0.05%). For the production of pea protein isolate, aqueous-solvent extraction method was used. The protein was extracted with an alkali solution from the ground pea-seeds and precipitated from the extract by bringing the pH down to isoelectric point (pH=4.5). The precipitated protein was separated from the supernatant by centrifugation. The effects of extraction parameters on the yield of extraction such as pH, particle size, temperature, solvent to solid ratio, and salt were studied. The maximum yields were obtained at these conditions
pH: 12.0 for the alkalinity of the extraction medium, 53 &
#956
m for the particle size, 40&
#61616
C for the extraction temperature, 5.0 for the solvent to solid ratio and 0.0 M for the saline concentration. At these extraction conditions, the maximum protein recovery was 72.75% resulting in a product containing 93.29% protein on a dry basis.

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13

Sakiyan, Demirkol Ozge. "Investigation Of Physical Properties Of Different Cake Formulations During Baking With Microwave And Infrared-microwave Combination". Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608181/index.pdf.

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The main objective was to determine the variation of physical properties of different cake formulations during baking in microwave and infrared-microwave combination ovens. In the first part of the study, rheological and dielectric properties of cake batter with different formulations were determined. Different concentrations of fat and different types of emulsifier and fat replacer were used. The variation of formulation had a significant effect on the apparent viscosity of the cake batter. Cake batter was found to show shear thinning and time independent behaviour for all formulations. Dielectric properties of cake batter were dependent on formulation, frequency and temperature. In the second part of the study, physical properties (dielectric properties, volume, texture, color and porosity) of cakes baked in microwave and infrared-microwave combination oven were determined. In addition, starch gelatinization during baking was investigated. For comparison, cakes were also baked in conventional oven. Formulation and baking time were found to affect physical properties and gelatinization degree of cakes. Addition of fat to the formulation was found to increase the dielectric properties and gelatinization degree of microwave and infrared-microwave combination baked cakes. For both microwave and combination baking, cake samples with SimplesseTM had the highest volume but the firmest texture. Addition of maltodextrin resulted in a more uniform structure for infrared-microwave combination baking. There was insufficient gelatinization in microwave baked cakes ranging from 70 to 78% depending on fat content. The gelatinization degree ranged from 88 to 93% in conventionally baked cakes. Combining infrared with microwaves increased gelatinization degree (80-90%).

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14

Uysal, Nalan. "Optimization Of Roasting Conditions Of Hazelnuts In Microwave Assisted Ovens". Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610384/index.pdf.

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The main objective of this study was to optimize the roasting conditions of hazelnuts in microwave-infrared and microwave-convective heating combination ovens by using response surface methodology. It was also aimed to construct regression models for the prediction of quality parameters of hazelnuts as a function of processing conditions. The independent variables were microwave power (10, 30, 50, 70 and 90%), upper-lower infrared power (10, 30, 50, 70 and 90%) and roasting time (2, 3, 4, 5 and 6 min) for microwave-infrared combination roasting. Microwave power (70, 140 and 210W), air temperature (90, 150 and 210°
C) and roasting time (5, 15 and 25 min) were the independent variables of microwave-convective heating combination oven. As control, hazelnuts roasted in conventional oven at 150°
C for 20 min were used. The quality parameters were L* value, a* value, fracture force and moisture content of the hazelnuts for both microwave assisted ovens. The optimum roasting conditions of microwave-infrared combination oven were determined as 2.5 min of roasting time at 613.8W microwave power, 1800W upper infrared power, and 300W lower infrared power. Hazelnuts roasted at the optimum condition had comparable quality with the conventionally roasted ones. When micro- wave infrared combination oven was used, conventional roasting time of hazelnuts was reduced by 87.5%. Optimum roasting conditions of microwave-convective heating combination oven were 140 W microwave power, 150°
C air temperature and 20 min roasting time. High regression coefficients were calculated between the experimental data and predicted values showing that RSM is capable in predicting quality parameters of hazelnuts during microwave assisted roasting.

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15

Aygun, Sukran Gizem. "Detection Of Gamma Irradiated Spices With Osl Method And Its Reliability". Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612333/index.pdf.

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The aim of this current work is to analyze the behavior of OSL (Optically Stimulated Luminescence) signals of irradiated spices with respect to time, temperature, origin and the type. Throughout the experiments, 3 different type spices from four different origins were stored at 4°
C and 25°
C for six months after irradiation. During experiments, unirradiated red pepper, thyme and cumin samples were analyzed by using OSL technique in order to determine the background OSL signal values of samples. Samples were irradiated 10 kGy by Cobalt 60 gamma source in TAEK (Turkey Atomic Energy Association). After irradiation process, OSL signal values of different samples were analyzed according to the given parameters. In order to determine the effect of temperature on OSL signal loss, temperature (4°
C- 25°
C) was set as storage temperature. The analyses were made monthly. According to the statistical analyses (ANOVA- General Linear Model), origin and type of samples were detected as significant parameters of design experiment. Time and temperature effect on OSL signal loss changed with respect to origin and type of samples. After six months storage period, OSL signal was lost for most of the origin and sample type. At the end of sixth month, an ESR analysis was performed to detect the accuracy of the OSL technique. With respect to the results of these experiments, it was seen that, due to optical fading, most of the samples was observed as unirradiated by OSL technique, however ESR analyze the samples as irradiated at the end of sixth month. Irradiation had a detrimental effect on the microbiological load of the samples and resulted 6 log reduction on the microbial population. After irradiation, no colony formation was observed in total bacteria and yeast- mold count. During six month period, no injury recovery was observed.

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16

Chiralertpong, Ariya. "Modifying coffee quality by chemical manipulation". Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/12425/.

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Chemical modification was applied to a coffee process by-product, silver skin, as well as raw coffee beans, with the aim to improve their aroma quality. Heat treatment in combination with sugar addition or enzyme treatment was applied to silver skin to encourage Maillard reactions. The manipulation applied to silver skin, however, did not give satisfactory results as the treatments neither caused significant increase in coffee aroma levels, nor yielded coffee aroma with quality resembling that of the real coffee. Chemical modification of raw Robusta coffee was carried out using fractionation and reconstitution approaches. The fractionation process involved the use of three types of solvent varying in polarity, dichloromethane (DCM), methanol (MeOH), and water, thus yielding four raw coffee fractions: DCM-soluble, MeOHsoluble, Water-soluble, and residue fractions. The reconstitution process involved wet mixing of the raw coffee fractions, vacuum drying and moisture content adjustment. Several reconstituted coffees were prepared with various proportions of the raw Robusta fractions, roasted and subjected to volatile analysis by Gas Chromatography-Mass Spectrometry (GC-MS). Statistical analysis by Principal Component Analysis (PCA) and the calculation of sum of normalized standard deviation (SNSD) of aroma compounds' odour activity values (OAVs) showed that the reconstituted Robusta that yielded the least variation, in term of aroma profile, from the higher quality coffee, Arabica, was the one composed of 70% d. b. MeOH fraction, 30% d. b. cell-wall material (residue), and 11 % w/w moisture content. The aroma profile of Arabica coffee was used as a reference due to its fine flavour that is commonly considered of better quality compared to that of Robusta (Briandet, Kemsley et al. 1996). Sensory evaluation (by sniffing) employing hedonic pairwise comparison technique confirmed the result from the GC-MS analysis that the aroma quality of the chosen reconstituted Robusta was improved since its aroma was significantly more preferred to that of the Robusta by the judges (30 people). Non-volatile compound analyses, however, suggested the need for further sensory study that involves tasting/drinking of the brews made with the new reconstituted Robusta for it contained significantly higher contents of bitter/astringent taste compounds, i.e. chlorogenic acids, caffeine and trigonelline, than the original coffees that could also affect the overall sensory quality of the coffee.

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17

Azhar, Mat Easa. "Factors affecting Maillard induced gelation of protein-sugar systems". Thesis, University of Nottingham, 1996. http://eprints.nottingham.ac.uk/11601/.

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Gelation due to the Maillard reaction took place when solutions containing a low level of bovine serum albumin were heated in the presence of carbonyl compounds. The Maillard reaction caused a change in colour, a decrease in the pH and induced gelation. These changes were dependent on the type and concentration of sugars or protein and on the heating conditions used. Reducing sugar and Maillard reaction products (e.g. glyoxal) affected these changes, yet their order of reactivity for browning and gelation were not necessarily the same. Loss of available lysine and arginine plus changes in the thio amino acids showed that these were implicated in the reaction. The gelation kinetics (gelation time and development of storage modulus) were followed in real time using a Bohlin CS Rheometer at a temperature of 90 °C. These studies showed that the gels did not form at a specific pH, the pH being lower for samples where the more reactive carbonyl compounds were used. Measurement of the charge on the protein after the Maillard reaction showed an increased negative charge, hence causing a lowering in the protein's isoelectric point. This had the effect of changing the critical protein concentration necessary for gelation at any pH above the isoelectric point. This reasoning would also explain the low syneresis seen in the Maillard gels. Hydrodynamic studies on dilute solution showed that the protein molecules heated in the presence of xylose associated in an orderly manner despite having a low pH. The aggregates could be described as "stiff and rod like". The linkages holding *the aggregates together were mostly attributed to additional non-disulfide linkages resulting from the Maillard reaction. Similar types of crosslinks were formed in the Maillard gels heated at 90°C and were thought to have enhanced the gel strength. Extrusion of soya grits with reducing sugars did not form a retort-stable product. However, microwave heating of the extruded product was successful in producing a product that survived a typical canning process. This suggests that formation of crosslinks may be controlled to produce novel food products.

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18

Barra, Giuseppina. "The rheology of caramel". Thesis, University of Nottingham, 2004. http://eprints.nottingham.ac.uk/11837/.

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The rheology of caramel was determined as a function of processing temperature and hydrocolloid additions. As the processing temperature increased the water content decreased and the caramel viscosity increased. X-ray diffraction showed that although crystalline fat was present, for the most part the sugars were in the amorphous state. The exception was the lowest water content caramel (7.9% water w.w.b.) which had been processed to a temperature of 122ºC. This had a small amount of crystalline fructose. Caramel rheology was assessed by rotational and capillary rheometry. Rotational rheometry gave information on the steady shear viscosity, the dynamic parameters (storage and loss moduli and related functions) and the creep compliance and recovery response. Capillary rheometry gave shear viscosities at high shear rates and an extensional viscosity. It was found that caramel without added hydrocolloids had behavior which was close to a Newtonian liquid. The only exception to this was the values obtained for the Trouton ratio which ranged from 10 to 40. This was considerably higher than the value of 3 for a Newtonian fluid and may reflect the difficulties in making measurements on these relatively low viscosity systems in the capillary rheometer. The viscosities obtained from steady shear, oscillation and creep were combined and three approaches were used to model the data as a function of measurement temperature and water content. An empirical statistical model using a second order polynomial, an Arrhenius fit and a Williams Landel Ferry (WLF) model. The former and the latter gave a good fit to the data although the constants used in the WLF model varied with the water content of the caramel. Arrhenius plots showed curvature particularly at low water contents. Incorporation of the hydrocolloids carrageenan and gellan gum into the caramel made the material non-Newtonian and elastic. For carrageenan incorporation in particular the Trouton ratio increased with carrageenan concentration reaching a value ~500 at a strain rate of 100s-1 for the caramel containing 0.2% carrageenan It was demonstrated that incorporation of carrageenan could be used to prevent cold flow in caramels processed at relatively high water contents. Glass transition temperatures were measured by differential scanning calorimetry and calculated from the temperature dependence of the shift factors used to superimpose the oscillatory rheological data. Generally there was agreement between the two approaches although for some gellan gum containing samples the rheological Tg was about 10ºC higher than the DSC value. Fragility calculated from the WLF constants for caramel was high as has been reported for sugars. The Tg for both caramel and sugar water mixtures calculated using the Couchman-Karastz equation in the water content of interest (9-15% w.w.b.) was some 30-40°C higher than measured. It is suggested that this disagreement could be related to the high fragility of the sugar water systems. Isoelectric point measurements using a streaming potential technique was shown to give information on the extent of the Maillard reaction and the presence of hydrocolloids.

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19

Yang, Ni. "Flavour reformulation and flavour stability". Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/12595/.

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ABSTRACT This project addressed two areas in the flavour industry – flavour reformulation required as a consequence of ingredient changes and flavour stability in solid food products. The aim of the flavour reformulation study was to evaluate both instrumental and modelling approaches to reformulate commercial flavourings for food products of different fat contents. A strawberry flavouring was chosen, which delivered an acceptable flavour in pectin jelly (0% fat) but did not perform so well in chewy candy (8% fat). Aroma release profiles in people eating these two sweets were measured by APCI-MS, the relative release differences for each flavour compound was determined and then used to reformulate the strawberry flavouring so its release in both sweets was similar. The sensory performance of candies confirmed a significant difference between the reformulated and original flavour (p < 0.05). The modelling approach was based on compound hydrophobicity (Log P) and the fat content of the food. This was used to estimate relative differences in flavour delivery for products with two varying fat contents. Flavourings were reformulated for yoghurt with reduce fat level, and the measured results showed good correlation with model’s prediction (r = 0.95). The aim of the flavour stability study was to explore the impact of product storage and flavour solvent in biscuits with vanilla flavouring. After eight weeks storage at 45 °C, up to 20% vanillin loss was measured, but sensory results suggested no difference in vanilla flavour perception. Texture analysis indicated that biscuits using triacetin (TA) as flavour solvent were more brittle than biscuits made with propylene glycol (PG). This was explained by X-ray CT analysis results which showed TA biscuits had larger pores than PG biscuits. Additionally, TA solvent provided higher vanillin stability during storage, so it should be a better choice than PG solvent used in flavourings for biscuits. IMPACT STATEMENT This research proved that it is feasible to apply laboratory-derived knowledge and adapt scientific techniques in a commercial context. It also demonstrated how the research findings can be transferred into the commercial field through two studies. The first study successfully illustrated two novel approaches to reformulate flavourings between food products of differing fat contents. Comparing with traditional trial and error process, this study demonstrated that instrumental and modelling approaches can be more effective ways for flavour reformulation in the flavour and food industry. The cost of flavour reformulation including the reformulation time and the cost in-use can therefore be reduced considerably. The results of this study have been presented to company’s major clients worldwide, and this has been applied commercially in a range of products including the successful reformulation of a £50 M (2010, brand value) soft drink into new formats (2011). The second study increased the understanding of the flavour stability within the stored food products. This ensured the flavour company to deliver high quality materials not only to their clients before food manufacturing, but also maintained its quality in the food products during storage for their end users. Comparing two flavour solvents – propylene glycol and triacetin, the results of this study suggested that triacetin is a better solvent as it offered better flavour stability in the stored biscuits. The findings can also be applied to reduce the cost in-use for vanilla flavouring in biscuit, which is especially beneficial for food and flavour company when high cost natural vanilla flavourings are required.

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20

Moreau, Lydie. "Impact of sodium chloride on breakfast cereal products". Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/28601/.

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To reduce the amount of sodium chloride in breakfast cereals without changing their properties, it is necessary to understand the role of this salt. Hence, a model system was developed. This model, composed of native waxy maize starch, glucose and a mixture of amino-acids generated similar colour and residual volatiles after heating compared to commercial breakfast cereals. Systematically designed experiments used this model to study the influence of NaCl concentration (0 % to 5.44 %) on colour, residual volatiles and acrylamide formation. It was found that higher NaCl concentration led to darker products (p<0.05) and significantly decreased acrylamide formation in the model systems. However, it did not have a significant impact on residual volatile levels. These findings were confirmed by observations made on wheat, wheat and rice mixture, com and rice commercial cereals. The impact of NaCl on colour and acrylamide formation indicated that this salt might influence Maillard and/or caramelisation rates and pathways. As NaCl is a plasticiser, it can allow the rubbery state to be maintained for a longer period during heating, improving reactants' mobility and Maillard reactions. However, it was found using the model systems mixed with several types of plasticisers (NaCl, KCl or trehalose), that the NaCl plasticising effect was not the major influence. The models also demonstrated that the hygroscopic behaviour of NaCl was not linked to its impact on colour and acrylamide formation. In investigating salt's influence on starch, native waxy maize, cassava or potato starch were mixed with NaCl (0 to 4 %; moisture adjusted to 20 %) and were heated at 230°C for 45 min. Microscopic observations, wide angle X-ray, viscosity, intrinsic viscosity and DSC data all suggested that starch was degraded by the heat treatment, and NaCl accelerated starch break down into smaller molecules, i.e. glucose. The glucose potentially formed could then caramelise, which might explain the NaCl impact on colour formation in model systems and breakfast cereals. Among other tested salts, CaCl[subscript]2 and MgC1[subscript]2 also enhanced starch degradation during a heat treatment. In studying glucose solutions containing salt (NaCl, CaCl[subscript]2 or MgCl[subscript]2) and heated between 180 and 230 °C, it was observed that salt enhanced colour formation via caramelisation (p<0.05). Mixtures of glucose, amino-acids and salt (NaCl, CaCl[susbscript] or MgCl[subscript]2), heated under the same conditions, showed that salt significantly decreased colour formation (p<0.05), which was most likely generated via Maillard reactions. Hence, salts could slow down Maillard reactions, explaining why lower acrylamide contents were found in model systems and cereal products when NaCl was present. As NaCl seems to influence Maillard and caramelisation reactions, decreasing or removing NaCl from breakfast cereal recipes might not only alter the salty taste but also the overall flavour. CaCl[subscript]2 and MgCl[subscript]2 seemed to have similar or even more impact on colour formation compared to NaCl. Adding these salts to breakfast cereal products with a low NaCl content was found to compensate for the colour loss. Adding CaCl[subscript]2 or MgCl[subscript]2 also improved the overall flavour of breakfast cereals, even though it did not compensate entirely for the taste loss.

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21

Jenkins, David Martyn. "The impact of dehydration and rehydration on brewing yeast". Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/29243/.

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In the brewing industry it is standard practice to propagate a pure yeast culture and inoculate (pitch) it into the fermentation vessel. Once fermentation is complete, yeast is recovered and reused in subsequent fermentations (known as serial repitching) until a decline in performance occurs or the required number of successive fermentations has been conducted. Propagation is currently required to initiate the entire process again, which requires additional equipment, energy, water inputs and time. It has long been proposed that Active Dried Yeast (ADY) offers an alternative method of yeast supply. Adoption of this innovation by the brewing industry has been low because of perceived issues with the fermentation performance of ADY, the availability of strains and hygiene concerns. In the current study the fermentation performance of ADY has been assessed with respect to viability, genomic stability, membrane integrity, yeast growth, attenuation, uptake of wort nutrients and aspects of flavour development. ADY requires rehydration before use and it has been demonstrated that viability is impaired in these slurries, though the extent of viability loss was dependent on strain and rehydration conditions. The source of cell death is unclear. Mitochondrial and genomic DNA integrity was assessed using a variety of techniques and shown to be unaffected by dehydration and rehydration. In contrast membrane integrity was affected. Changes in membrane fluidity, sterol content and fitness to perform could be detected in ADY. Performance of ADY in fermentation was also impaired. A lag in cell growth, attenuation and sugar and amino acid uptake were noted. Diacetyl formation occurred more rapidly and end fermentation diacetyl levels were higher for ADY. These differences were not maintained during serial repitching. It is proposed that ADY could be utilised to replace freshly propagated yeast, but direct addition to fermenters would require an improvement of performance during the first fermentation.

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22

Norton, Clive. "Texture and hydration of expanded rice". Thesis, University of Nottingham, 1998. http://eprints.nottingham.ac.uk/11620/.

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The differences between conventionally processed and extruded puffed rice were examined, with a view to determining the reasons for their different storage behaviour in confectionery. Differences between the two forms of puffed rice have been identified, both in their performance and their properties. Under certain viewing conditions, the starch granules in conventionally processed and extruded rice appear to be different. The starch granules in conventionally puffed Rice remain intact, but with no crystalline structure (i.e. no Maltese crosses are visible, though starch ghosts are abundant.) Cell walls of conventionally processed rice appear to be a layer of these gelatinised intact granules. The ghostlike granules have not undergone notable swelling, remaining slightly greater than 10μm in diameter, similar to the size of unprocessed granules. In contrast, the starch granules in extruded puffed rice are rarely visible, in either their birefringent Maltese cross form, or as gelatinised but intact ghosts. By altering the extrusion conditions, the microscopic appearance of the product and its behaviour in water or water vapour becomes similar to that of conventionally processed rice. The extrusion parameters required for this similarity to conventionally processed rice fall within a window that is relatively narrow when compared to the ranges of variables available. Under more severe processing conditions the granules lose their integrity because shear and heat disrupt them. Under less severe conditions, the granules form clusters that do not gelatinise. The conditions at which this product is made cannot be interpolated or extrapolated from samples made under other conditions. However, at these extrusion parameters, the extrudate does not expand. It is necessary to expand the extrudate separately from the extrusion process. A novel method for the analysis of multi-peak force responses from compression of low moisture puffed cereal products was developed. This enabled crisp and crackly to be distinguished instrumentally. The results correlated well with sensory evaluation.

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23

Tran, Thierry. "Puffed rice and the molecular changes that determine its structure". Thesis, University of Nottingham, 2003. http://eprints.nottingham.ac.uk/14318/.

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The Rice Krispies™ process consists essentially of the cooking of short or medium rice grains, followed by a mechanical compression between two rolls (bumping), a tempering step and a toasting operation (puffing) which expands the grains into the finished product. The objectives of this project were to clarify which molecular phenomena take place inside the rice grains during the process and to facilitate the improvement and optimisation of the process parameters. The composition and gelatinisation behaviour of seven different raw rice varieties used either in the United States or the United Kingdom were studied. The glass transition of the cooked rice material was determined by dynamic mechanical thermal analysis (DMTA), which allowed each step of the process to be mapped onto a temperature / moisture content state diagram. The bumping step of the process and its effect on the various molecular entities present in the cooked rice were studied in details. Amylose was found to form complexes with the lipids present in the material during cooking, and these reinforced the cooked rice grain structure. One of the roles of the bumping could be to partially dislocate these amylose-lipid complexes to enable the rice grains expansion at the puffing step of the process. The bumping also reduced the molecular weight of amylopectin, which is thought to weaken the rice grains structure and improve the puffed grains expansion. The mill gap between the bumping rolls was the key factor determining the quality of the puffed product. The temperature at which the rice grains are bumped had a secondary influence on the quality of the puffed rice, within the range 26°C to 57°C. The RVA provided a very effective method to categorise post-bumped samples and could be a useful diagnostic tool in case of production problems. Evidence of physical ageing and moisture content equilibration during the tempering step was found. Physical ageing did not have a detectable effect on the expansion of the rice grains, while it was important that moisture content was equilibrated inside the grains to ensure a proper puffing. Finally, correlations were found between the puffed rice grains expansion and the post-bumped grains height recovery, which made it possible to predict the quality of the expanded grains from the characterisation of the post-bumped rice. Overall, the project is a good example of the application of general starch science concepts to the study of a specific industrial process.

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24

Mat, Taher Zarani. "The impact of upstream and downstream processing on the quality of oil bodies of partially de-hulled sunflower seeds". Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/38480/.

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Few publications on oil bodies or oleosomes seem concerned about their quality (chemical and physical) ex-vivo. This work attempts to identify the main factors (processing and pre-processing) that affect the quality/integrity of sunflower seed oil bodies recovered through a wet-milling process. The physical state of seeds during wet milling had a significant impact on the quality of the oil body suspension. Pre-soaking for 6 hours before wet milling and multiple washing with alkaline buffer (0.1M sodium bicarbonate) was performed to isolate high quality oil body suspensions. It was evident from different physical measurements such as particle size, ζ-potential and light microscopy that pre-soaking had a positive influence on the quality of oil body suspensions with no significant signs of aggregation or coalescence. It was also observed that the resultant washed oil body suspensions were highly surface charged (-28.4 ± 1.2 mV) indicating very stable suspension phase behavior. Washing oil bodies not only removes non-integral, extraneous proteins (derived from the seed matrix) but enriches the lipid content including Tocopherol (α-tocopherol: 491.6 mg/kg of washed oil bodies compared with 252.6 mg/kg crude oil bodies). Changes in the composition of oil bodies after washing have been observed before, but this research also monitored the size of oil bodies after washing, and our results indicate that certain factors can shift the distribution of droplet size. It is believed that any change in average size of droplets indicate the presence of disrupted oil bodies whose surface chemistry has changed enough to compromise their integrity on washing. The retention of droplet size on washing may, therefore, be diagnostic for the recovery of intact oil bodies. An assessment of the integrity of oil bodies recovered from sunflower seeds after accelerated aging (5 months) was carried out. Free fatty acid was more pronounced in oil rather than oil bodies, this could be due to the elimination of some of the free acid bound to oil body during washing. Although some minor variation was observed during seed aging, however, the oil bodies remained stable in the final suspension. The results indicate that oil body membrane was extremely robust under extreme conditions and the integrity of oil bodies was preserved. In addition, oil bodies obtained in this study were resistant to oxidation due to the presence of naturally occurring antioxidants (including vitamin E) associated with them. The results indicate that the physical barrier of surface membrane protein (oelosin) protect oil bodies against pro-oxidants.

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25

Maxminer, Joerg. "Assessing the flavour stability of lager-style beers". Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/36976/.

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Beer, as manufactured, is not at chemical equilibrium and undergoes complex chemical reactions during storage which can lead to undesirable changes in the sensory characteristics of beer. Since beer contains more than 600 volatile compounds, beer flavour change is a complex field of research and the dependable prediction of shelf life remains a top research priority. Chapter 1 places the work described in this thesis into this context. Chapters 2 and 3 provide details of the experimental methods used and their development, respectively, to evaluate flavour stability. The methods used and developed include: (i) the determination of one of the major antioxidants present in beer, sulphur dioxide (SO2), via distillation; (ii) a solid phase micro extraction (SPME)-GC-MS method with on fibre derivatization as a reliable detection method for aldehydes related to off flavours perceived in aged beer; (iii) measurement of the oxidative stability using electron paramagnetic resonance (EPR) spectroscopy. Chapter 4 describes oxidative stability measurements via EPR spectroscopy for three different lager-style beer qualities pre- and post-filtration. The trial included a large scale Kieselguhr frame filter, and two pilot-scale membrane filtration system. The results illustrate how EPR spectroscopy is sensitive to metal ion pick-up from traditional filter media and oxidative stability measures were evaluated versus oxygen pick up during filtration and sulphur dioxide content of the beer samples. The effect of a brewhouse addition of gallotannins on the flavour stability of a lager-style beer was investigated in Chapter 5. Pilot scale (16 hl) and large scale production line (1500 hl) experiments with gallotannins additions in the Brewhouse were performed. The effects of the different additions were monitored at key points of the production process and through to the final beer. Despite showing significant improvements in the pilot scale wort samples, the results for the related packed beer samples did not show clear flavour stability improvements. For the production-scale trials, only a very limited effect of improved flavour stability could be observed. In Chapter 6 a factorial experimental design was adopted to probe the interactions between seven factors known to impact on beer flavour stability. Chemical additions were made to a bright beer prior to bottling, to vary the following factors: total in pack oxygen, SO2, total iron, iso-α-acid and α-acid content, (+)-catechin and glutathione. Increased SO2 concentrations had the largest impact across the entire design space, resulting in reduced radical formation, staling aldehyde concentrations and improved sensory scores. The impacts of increased TIPO levels were rather limited. In contrast, a significant impact regarding the oxidative stability could be observed for increasing Fe concentration, highlighting the significance of pro-oxidative effects of transition metals.

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26

Oladokun, Olayide. "The quality of bitterness in beer". Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/43415/.

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The bitterness of beer remains one of its most important flavour attribute. However, complexity surrounding bitterness perception alone represents a significant challenge in its understanding, in addition to other factors relating to production processes and raw materials used in making beer. The aim of this research was to better understand beer bitterness in terms of its intensity and quality, and how hopping technology (e.g. quantity and time of hop addition during the brewing process), hop aroma and variety may effect perceived bitterness intensity and quality. This project combined both analytical and sensorial analysis, and used statistical techniques to identify the key compounds driving bitterness perception. Analytical techniques were employed to quantify bitterness-contributing compounds and analytical bitterness units in beers alongside descriptive analysis of perceived sensory bitterness. Perceived sensory bitterness (both qualitative and quantitative) was assessed using a purpose developed list of well-defined bitterness attributes, to aid the characterisation of bitterness quality in beers. The impact of cross-modal flavour interactions on the perception of beer bitterness intensity and qualities was also investigated at varying analytical bitterness levels. Lastly, the effect of hop variety, and how this significant raw material affects perceived bitterness quality was also investigated using three distinctively different hop varieties (Hersbrucker, East Kent Goldings and Zeus). Results revealed a significant impact of the analytical profiles of beers, derived from the type of hop products and hopping technology adopted in beer production, on the perceived bitterness quality of beer. In general, beers high in hop acid compounds and polyphenols were, as expected, perceived to be higher in bitterness intensity. The results further showed that bitterness intensity also played a role in the perception of bitterness quality i.e. whether the beer was ‘harsh’, ‘lingering’ or ‘round’. However, beers high in these compounds were not always of ‘negative’ bitterness quality, and correspondingly lower amounts of these compounds did not always result in ‘positive’ bitterness qualities in beer. Results on the impact of cross-modal flavour interactions showed that hop aroma plays a crucial role in beer bitterness perception, and can modify the perception of bitterness intensity and quality as well as temporal profiles of bitterness in beer depending on analytical bitterness levels. The investigation into the impact of hop variety on perceived bitterness quality revealed hop-derived bitterness profiles relating to individual hop varieties, and further suggests that careful selection of the hop variety used for brewing is important for controlling perceived bitterness quality. This research provides a comprehensive interdisciplinary approach to understanding perceived beer bitterness and its associated qualities, with findings suggesting that besides bitterness intensity, the quality and overall impression of bitterness as perceived by consumers are significantly influenced by raw materials, production processes and other factors such as aroma which might be overlooked by brewers - but are likely to be significant for consumer preference and the success of a brand.

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27

Mott, Alexander Charles. "The relationship between very high gravity fermentations and oxidative stress in the lager yeast Saccharomyces pastorianus". Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/40232/.

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Very High Gravity fermentations are an increasingly attractive proposition within the brewing industry as a means of energy saving and optimising process efficiency. However, the use of very high gravity ( > 20°P) wort is associated with a range of biological stress factors. Ethanoic and osmotic stresses have been widely analysed along with oxidative stress in relation to propagation and early stage fermentation. The aim of this research was to investigate the impact of wort gravity on oxidative stress, and understand how this affects the plasma membrane at VHG. Finally the effect altered ergosterol content was analysed. The characteristics of Saccharomyces pastorianus strains were assessed for their ability to withstand the increased pressures of VHG (22°P) fermentations. VHG fermentations showed increase ethanol production at the expense of fermentation length, and increased ethanol production during VHG fermentations was offset by an increase in fermentation length. All fermentations were observed to accumulate ROS and increased antioxidant levels, with levels being furtherelevated in the VHG environment. Further analysis of S. pastorianus strains indicated that the levels of oxidative stress observed in fermentation had a negative effect on membrane fluidity and increased damage of the plasma membrane was observed. Analysis of ergosterol enriched yeast indicated that although fermentation rate was increased, a trade off with alcohol and biomass production was observed. Furthermore in response to oxidative stress, ergosterol enriched yeast showed reduced tolerance, decreased membrane fluidity and increased membrane damage. This work will give further insight into the response of lager yeast to oxidative stress present during VHG fermentations.

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28

Boothroyd, Emily L. "Investigation of the congeners responsible for nutty/cereal aroma character in new make malt whisky". Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/50903/.

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The nutty and cereal aromas of new make malt whisky are important sensory characteristics of certain distillery malts of commercial value for blending; however there is a lack of understanding regarding the volatile congeners which contribute to these complex sensory characters. The work described in this thesis aimed to improve knowledge of the chemical origins of nutty and cereal aromas in immature spirit in order to aid process control of these characters during manufacturing. Two aroma extraction methods were compared; liquid-liquid extraction (LLE) using dichloromethane and solid-phase extraction (SPE) with LiChrolut EN sorbent. New make spirit samples from industry (n=S) were evaluated by a trained whisky sensory panel using Quantitative Descriptive Analysis (QDA). Four were noted for their nutty/cereal character, the other served as a non-nutty control. Gas Chromatography-Olfactometry/ Mass Spectrometry (GC-O/MS) was used to try and identify compounds in chromatogram regions coincident with nutty/cereal descriptors. Using LLE extracts, 14 such regions were identified. LiChrolut EN SPE proved to be more selective (19 nutty/cereal odour active regions). 2,S-dimethylpyrazine (known to impart a nutty/cereal character in other food systems) was one noted congener, which was only detected using the more selective SPE method. The gross volatile compositions of the 5 spirit samples were remarkably similar, suggesting that congeners present at low concentration but with low odour thresholds are likely responsible for nutty/ cereal characters. One analytical difference of note was that the nuttier samples contained higher concentrations of long-chain esters. Thus, ethanolic Atmospheric Pressure Chemical Ionisation Mass Spectrometry (APCI-MS) was used to analyse the headspace concentrations of a test set of 14 whisky aroma volatiles above a series of aqueous ethanolic solutions differing in concentrations of alcohol (5 -40% ABV) and ethyl hexadecanoate (O-SOO mg/L). Ethanol had a significant solubilising effect (p < 0.0001) on headspace volatile concentrations of all the aroma compounds, whilst the ethyl hexadecanoate concentration had a selective effect of reducing headspace concentrations of the more hydrophobic aroma compounds (Log P > 2.S). We propose that nutty and cereal characters are imparted by relatively polar aroma compounds, whose characters are emphasised by the selective incorporation of hydrophobic aroma compounds into the interior of micelle-like structures formed by long chain esters (typified here by ethyl hexadecanoate). Some distillers have reported that manipulation of the lipid concentrations in wash offers a method of controlling the nutty/oily character of new make spirit. A batch of fermented wash sourced from industry was spiked with varying concentrations of oleic (18:1) and linoleic (18:2) acids and (laboratory) distilled at two different temperatures, using a D-optimal experimental design to evaluate the impacts of each factor. Nutty (p = 0.0203) and oily (p = 0.0034) aroma characteristics were scored as significantly stronger in distillates of wash spiked with 100 Ilg/mL each of oleic and linoleic acids, as compared to the control. GC-O/MS of distillate extracts once again determined several odour active regions relevant to the nutty/cereal characters and concentrations of some compounds could be correlated with nutty/cereal QDA scores. New make spirit samples from 35 individual malt whisky distilleries were extracted using the LiChrolut SPE method and analysed by GC-MS. Analytical concentrations of 'candidate' nutty-cereal compounds (n = 20) were used to model sensory QDA data for the 35 spirit samples (nutty, oily, cereal and feinty characters) using Principal Components Analysis (PCA). Significant positive correlations with nutty were seen for 7 compounds (using ANOVA). These included the Maillard products 2-furanmethanol (p < 0.0001), 2-methylpyrazine (p < 0.0013) and 2,5-dimethylpyrazine (p < 0.0004). The PCA overlay bi -plot showed clustering of certain higher alcohols near to the nutty aroma descriptor (methionol, pentan-1-0I, 2-phenyethyl alcohol). Nutty and cereal characters of whisky are of complex origin and likely originate from multiple congeners in a synergistic mixture. This work has shown that processes of particular importance to the expression of this character in new make spirit are lipid oxidation and Maillard chemistry. The conditions for these reactions are to be found during malt kilning and distillation. Whilst these processes are where nutty/cereal compounds are likely to be formed, other distillery parameters such as the mashing protocol, length of fermentation (both determine the supply of key precursors such as fatty and amino acids) and the spirit cut of the distillation govern the chemical composition of the final spirit.

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29

Holmes, Calum P. "An optimised sorghum brewing process". Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/30603/.

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Whilst there is a tradition of indigenous opaque sorghum beer production in Africa, the manufacture of Western-style clarified lager beers from sorghum is a relatively recent development, originating in late 1980’s Nigeria. There remains substantial scope to optimise the process by tailoring the equipment and conditions utilised more specifically to the raw material. This was the context to the main objectives of this PhD project: towards an improved sorghum brewing process. Two principal approaches were employed: 1. The reduction of primary energy usage by developing novel modifications to the mashing and wort boiling unit operations and 2. Characterisation of the material properties of a substantial co-product of sorghum brewing, sorghum spent grains (SSG) as a pre-requisite to assessing its suitability for the production of value-added products and/or biofuel. The gross chemical composition of five SSG samples sourced from commercial breweries in Africa were determined, with the sum of individual components accounting for 97.8 % material on a dry weight basis (d.b.; average value). The SSG samples contained relatively high amounts of protein (>38.0 %) as compared to values quoted for brewers’ spent grains. SSG samples were found to contain considerable amounts of residual starch (>4.55 %; d.b.), which suggested that the practice for milling and mashing with unmalted sorghum, in the breweries from which samples were sourced, could be further optimised. By boiling at reduced temperature, required energy input is reduced as the latent heat of evaporation is not provided. In Chapter 3, the impact of reduced temperature boiling on the formation and stripping of key wort volatile compounds was evaluated at both industrial scale and pilot scales (10 hL). As compared to control boiling (3.5 % evaporation), the stripping efficiency of simmer boiling (0 % evaporation) was reduced for some volatiles, including: hexanal, linalool, and β-myrcene. One key lager flavour volatile, dimethyl sulphide (DMS), displayed similar patterns of stripping when comparing simmer and control boils. In Chapter 4, we report the evaluation of a novel wort boiling technology in production-scale trials at a brewery in Ghana. The ‘PDX’ wort boiler utilises direct steam injection into wort and claims improved efficiency of heat transfer and volatile stripping. The present work demonstrated that steam injection technology could provide an approximate 50 % reduction in energy input during the boil, without significant deleterious effects on final product quality. Finished beverages produced using steam injection technology were determined to be within brand specifications by a trained sensory panel. Chapters 5 and 6 report investigations aimed at reducing the energy input when mashing with unmalted sorghum and developing knowledge of how the structure and composition of different sorghum cultivars interacts with the mashing conditions employed. Designed experimentation was used to investigate the impact of mash conditions on a novel low-temperature mashing system and a high-temperature enzyme mashing system. The reduced energy, low-temperature system was comparable to the high-temperature system in terms of extract and FAN yield, when mashing with unmalted Sorghum bicolor cv. Fara Fara. Furthermore, both enzyme systems were able to produce acceptable wort using agricultural sorghum varieties, providing that the starch properties were similar to brewing cultivars in terms of their pasting characteristics and grain hardness. Poor mashing properties were associated with cultivars displaying increased physical interaction of endosperm protein with starch, resulting in reduced starch swelling during mashing.

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30

He, Qi. "Understanding the sensory perception of hydrocolloid thickened systems based on flow and lubrication behaviour". Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/14203/.

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This thesis seeks for a better understanding of the sensory properties of hydrocolloid thickened foods during oral processing through studying both flow and lubrication behaviours. In addition, during oral processing, saliva plays an important part through mixing with samples, and it is therefore the mixture of foods and saliva that is perceived. However, the role of saliva in sensory perception is not fully elucidated. This research also features a preliminary study on both flow and lubrication properties of saliva in presence of the 5 basic tastants and also how lubrication properties of hydrocolloids are changed when mixing with saliva. Two groups of five samples were designed to have either similar viscosity at a shear rate of 50 s-1 or 105 s-1 by varying the concentrations of xanthan and dextran with the aim to find out which shear rate(s) is related to mouthfeel perceptions. Samples had the same levels of sucrose and banana flavour (isoamyl acetate) added to them and the flavour release and in mouth perceptions measured. The flow behaviour of samples were further characterised in small amplitude dynamic oscillatory shear and stretch flow. A trained sensory panel generated and evaluated mouthfeel, aroma and taste attributes of these solutions. Sensory results indicated that both low and high shear viscosity were related to mouthfeel perceptions. Models including both low and high shear viscosity values predicted the ‘Thickness’ perceptions better than the models including a single shear viscosity. Stickiness and mouthcoating perceptions were better predicted through models including both low shear viscosity and extensional viscosity. Mouthfeel perceptions were also found to be related to complex viscosity at angular frequency of 100 rad.s-1. In terms of sweetness perception, it was affected by the low shear viscosity. However, for samples having similar low shear viscosity, higher scores of overall sweetness were given to samples that were less shear thinning. The high shear viscosity of hydrocolloid samples determines the lubrication properties. Samples with higher viscosity at high shear rate were found to have lower friction in mixed regime but higher in hydrodynamic regime. The mouthfeel perceptions were found to be correlated with friction coefficient at speed of 40-100 mm/s and flavour and aroma were negatively correlated with friction coefficient at speed of 10-30 mm/s. The flow and lubrication behaviour of saliva is changed significantly when stimulated by five basic tastes. The presence of saliva mixed with hydrocolloid samples reduced the friction by up to two orders in boundary and mixed regime but did not affect the friction in hydrodynamic regime which is more related to mouthfeel perceptions.

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31

Zhuang, S. "The relationship between high gravity brewing, key performance indicators and yeast osmotic stress response". Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/27767/.

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High Gravity (HG) and Very High Gravity (VHG) fermentations are increasingly attractive within the brewing industry as a means of energy-saving and to optimise process efficiency. However, the use of highly concentrated worts is concomitant with a number of biological stress factors and in particular elevated osmotic pressure, which can impact on yeast quality and fermentation performance. In order to eliminate or reduce such negative effects, yeast cells often respond to their environment by adapting their central carbon metabolism and by making osmotic adjustments. The aim of this research was to investigate the impact of wort gravity on carbon flux, key performance indicators and to examine the effect of external osmolality (as a measure of osmotic pressure) on cell physiology. The fermentation performance of lager and ale brewing yeasts in standard (13 °P), HG (18 °P) and VHG (24 °P) worts was assessed with respect to the uptake of wort sugars, and the production of key carbon metabolites. Estimation of carbon partitioning revealed that products including trehalose, glycogen, higher alcohols and esters had only minor effects on carbon distribution, whereas the production of yeast biomass acted as a major trade-off with ethanol production. Moreover, parallel analysis of the fermentation environment indicated that osmolality increased during fermentations, particularly at high gravities, with the largest contribution directly related to ethanol production. Consequently, yeast cells were subjected to a series of increasing osmolality levels induced by sorbitol, designed to replicate high gravity conditions. These conditions were shown to have a negative impact on yeast viability and vitality, although cell genome integrity was unaffected. In addition, cells responded to osmotic pressure by modifying membrane components leading to a change in fluidity, and by promoting glycerol production. It is anticipated that the data presented here will provide a greater understanding of the response of yeast to HG and VHG conditions, potentially leading to process optimisation in the future.

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32

Johansson, Joanne. "Incorporation of hydrocolloids into pet food for new applications". Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/36249/.

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This thesis investigates how hydrocolloids can be incorporated into pet food meat products to provide novel applications. The possible applications that have been investigated for hydrocolloids are satiety and the production of more sustainable meat products. The research was carried out to improve canned pet food and the processes used to manufacture the product. The main section of the thesis looks at incorporating alginate and pectin solution into a food product which then becomes a gel in a low pH environment. The gel produced in the stomach should produce a satiety effect within the pet. Hydrocolloids used in other studies have been shown to induce satiety in humans. The gel was tested in vitro with a positive result which showed good gelation; however, when tested in vivo, no reduction in food intake was seen. These results may indicate that satiety has different trigger mechanisms in dogs compared to humans. More research is needed to understand whether dogs have the same hormonal responses to satiety as humans. The second application was the use of agar and methylcellulose (MC) to produce a thermally stable gel. The incorporation of this gel structure into a wet meat product would allow the level of meat to be reduced and additional powders to be used as a nutrient component instead. A thermally stable gel also enables the pet food to be processed more efficiently. The gel allows the meat chunks to be cut at high temperatures; therefore, no cooling step is needed in production. Agar and MC produce a strong thermally stable gel at both high and low temperatures. There is evidence that an interpenetrating network is formed in which the molecular ordering and aggregation of the individual polymers appears to be affected by the presence of the second polymer. The use of hydrocolloids for new applications in meat will transform and improve the quality of these products in the future.

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33

Shahari, Nor Azni. "Mathematical modelling of drying food products : application to tropical fruits". Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/12485/.

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Drying is an old traditional method of removing liquid from inside material, suchas wood, food, paper, ceramics, building materials, textiles, granular products, pharmaceutical and electronic devices. The kinetics of this liquid removal depends on the material properties of the solid phase as well as on cellular structure. The aim of this project is to understand the effect of complex interaction of heat, moisture and shrinkage to create a detailed mathematical modelling to quantify the drying of a food product and tropical fruits in particular, which typically have high water content. To this purpose, in first part of the thesis, an initial simple coupled diffusion model with Fickian moisture transfer and Fourier heat transfer by Wang and Brenann [122] has been extended. A one-dimensional model is applied with the effect of shrinkage for a prediction of moisture and temperature distribution during drying. Constant physical and thermal properties are used relevant to tropical fruits. A numerical solution technique, based on the method of lines, is used with local finite difference methods approximation to the drying. The results match well with published food drying simulation studies and the anticipated final state of shrinkage in particular. To obtain a detailed understanding of simultaneous heat and liquid transfer during drying of fruits, the internal structure has to be modelled. In fruit tissue, intercellular space existing within a highly complicated network of gaseous channels can be considered as a porous medium. Guided by this, an extended model of drying, incorporating the heterogeneous properties of the tissues and their cellular structure, is recognized and simplified to represent the physical model. In this model, a distinction is made between the different classes of water present in the material (free water, bound water and water vapour) and the conversion between them. Evaluation is applied to the range of one-dimensional structures of increasing complexity: the first is an isothermal model without consideration of heat effects; the remaining have heat effects but differ in the correlated spatial arrangement of micro and macro pores. All results are given as drying curves and phase distributions during drying.

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34

Gungor, Ugras. "Design Of A New Equipment For Sesame Seed Dehulling". Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/678/index.pdf.

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In this study, new methods and processing equipments for sesame dehulling were investigated. First, water absorption of sesame seed was studied at 20, 30, and 40°
C. The data could be modeled using Peleg equation where it was found that the constant k1 was inversely related to temperature but the effect of temperature on k2 was negligible. In the second phase of the work a lab scale continuous screw conveyor as dehuller and two equipments, (1) fluidized bed dryer and (2) hull separator to function as agitator, dryer and separator, for hull separation were designed. Fluidized bed unit was unsuccessful as it caused rapid drying of seeds before hulls can be removed. Using designed dehuller and hull separator, seeds at 30.5, 50.4 and 70.7 % db moisture contents were processed at dehuller speeds of 420, 840, and 1150 rpm. It was found that the percentage of dehulled seeds was linearly dependent on moisture content, optimal speed of designed dehuller was 840 rpm, and results for the efficiency of dehulling the seeds were significantly the same at 420 and 1150 rpm. Repeated passes of seeds through dehuller not only increased the efficiency of dehulling but also the percentage of damaged seeds. A dehulling efficiency of about 92.5 % was attained after four passes. The possibility of soaking seeds in an enzyme solution before dehulling was also investigated. By this means, after soaking in 0.2 % (v/v) Peelzyme-I solution for 15 min, a dehulling efficiency of 95 % was achieved.

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35

Dogan, Seyhan Firdevs. "Effects Of Different Batter Formulations On Quality Of Deep-fat Fried Chicken Nuggets". Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605088/index.pdf.

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The main objective of this study was to evaluate the effects of different flour and protein types on quality of deep-fat fried chicken nuggets. Additionally, the rheological properties of batters were studied and the batter viscosity was correlated with fried product quality. In the first part of the study, the effects of soy and rice flour (5%) addition to the batter formulation on product quality were studied. Coating pick-up of batters, and moisture content, oil content, texture, color, volume, porosity, and cooking yield of nuggets were determined for 3, 6, 9 and 12 minutes of frying times at 180º
C. In the second part of the study, the effects of protein types (soy protein isolate, whey protein isolate and egg albumen) at different concentrations (1 and 3%) on quality attributes were studied. A batter formulation with no flour or protein addition was used as control. In both parts of the study, flow behavior of batters prepared using different flour and protein types were determined. Soy flour and soy protein isolate (SPI) provided the highest apparent viscosity. Batter viscosity was found to be correlated with coating pick-up. All batters were found to show thixotropic behavior. The batters were modeled as power-law fluid and all of them turned out to be shear-thinning except egg albumen added batter, which was shear-thickening. As a result of the study, among the flour and protein types used, 3% whey protein isolate (WPI) was found to be the most effective ingredient on improving quality parameters of deep-fat fried chicken nuggets. 3% WPI added batters provided the hardest and crunchiest product with the darkest color. It also reduced the oil content of fried nuggets significantly. However, low cooking yield values were observed for batters with 3% WPI. On the other hand, soy flour containing batters provided high cooking yield. Therefore, if high cooking yield with low oil content is desired, soy flour can be advised to be used in batter formulations for chicken nuggets.

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36

Ozcan, Evren. "Ultrasound Assisted Extraction Of Phenolics From Grape Pomace". Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12606908/index.pdf.

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Grape pomace is a by-product of wineries. It is one of the most potent antioxidant sources due to its high phenolic content. In this thesis study, ultrasound assisted extraction of phenolic compounds from Merlot grape pomace has been studied. The effects of sonication time, subsequent extraction time in shaking water bath at 45°
C and composition of the solvent on extraction efficiency and recovery of phenolics were studied by response surface methodology. Folin-Ciocalteu colorimetric method was used to analyze effects of process parameters on the total phenolic content of the extracts. The best recovery (47.2 mg gallic acid equivalents of total phenolics per g of dried grape pomace) was obtained using 30 % aqueous ethanol and applying 6 minutes of sonication followed by 12 minutes of shaking in water bath at 45°
C.

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37

Kahyaoglu, Leyla Nesrin. "Usage Of Spouted Bed And Microwave Assisted Spouted Bed Dryers In Bulgur Production". Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610856/index.pdf.

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The main objective of this study was to investigate the effect of spouted bed and microwave assisted spouted bed drying on drying rates and quality parameters of bulgur. The drying experiments were performed at three air temperatures (50, 70, 90oC) and at two microwave powers (288 W, 624 W). Quality parameters were selected as bulk density, apparent density, apparent porosity, internal porosity, microstructure analysis, and color for dried cooked wheat
yield and water absorption capacity for bulgur. The drying rate increased with air temperature and microwave power. Microwave assisted spouted bed drying at microwave power of 288W and 624 W reduced drying time by at least 60% and 85%, respectively compared to spouted bed drying. The effective moisture diffusivities of bulgur in the spouted bed and microwave assisted spouted bed drying were found to be 2.356x10-10 and 8.398x10-10 m2/s on the average, respectively. The effect of air temperature on product quality except color was not significant in spouted bed drying. Interior kernel porosity, sphericity and L* value of dried cooked wheat increased with air temperature and microwave power. Yield and water absorption capacity of bulgur tended to decrease as microwave power increased. According to SEM analysis, more porous structure was observed in wheat samples dried in microwave assisted spouted bed compared to air dried ones. In microwave assisted spouted bed drying, lower water absorption capacity, bulk density and apparent density, higher sphericity and lighter color were observed as compared to spouted bed drying.

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38

Luca, Alexandru. "Effect Of Nanoencapsulation Of Purified Polyphenolic Powder On Encapsulation Efficiency, Storage And Baking Stability". Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614412/index.pdf.

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The primary objective of this study was to obtain nano-emulsion containing polyphenolic compounds extracted from sour cherry pomace and to investigate the effect of degritting of polyphenolic concentrates on the encapsulation efficiency and particle size distribution of capsules and emulsions. It was also aimed to study storage and baking stability of the capsules. Extracted polyphenolic concentrate was degritted at 10,000 rpm for 2 min. Purification reduced Sauter mean diameter (D[32]) of concentrated extract from 5.76 &mu
m to 0.41 &mu
m. Unpurified and purified concentrates were freeze dried for 48 h to obtain extracted phenolic powder (EPP) and purified extracted phenolic powder (PEPP), respectively. Powders were entrapped in two types of coating materials which contain 10% maltodextrin (MD) or 8% MD-2% gum arabic (GA). Samples were prepared by ultrasonication (160 W, 50% pulse) for 20 min. Emulsions containing EPP had D[32] of 1.65 and 1.61 &mu
m when they were entrapped in 10% MD and 8% MD-2% GA coating material solutions, respectively. It was possible to obtain nano-emulsions when purification step was performed. Emulsions prepared with PEPP and coated with 10% MD and 8% MD-2% GA had D[32] of 0.396 and 0.334 &mu
m, respectively. Encapsulation efficiency of the capsules increased significantly from 86.07-88.45% to 98.01-98.29% by means of degritting (p&le
0.001). Loss of total phenolic content during storage at 43% and 85% relative humidities was smaller for encapsulated powders when compared to powders not entrapped in coating material. In addition, encapsulation significantly increased retention of phenolic compounds from 15.1-22.2% to 30.4-30.7% during baking (p&le
0.05).

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39

Xia, Wei. "Exploitation of low value food materials as a novel source of flavour enhancers". Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/48128/.

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There is demand from the food industry for novel savoury seasonings based on low-cost food ingredients, sourced from within the EU. A nucleotide and protein rich spray dried powder which was derived from a Fusarium venenatum fermenter waste stream and food-grade Alphitobius diaperinus with potential as a savoury flavour enhancer was evaluated. Enzymatic digestion of these two raw materials as a source of flavour precursors was evaluated. Serial enzyme combinations, enzyme dosages, sequence of enzyme application, pH, temperature and length of digestion for the liberation of amino acids and nucleotides were optimised for the liberation of taste active compounds. For amino acids, free glutamine (GLN) and glutamic acid (GLU) could be enhanced using a combination of peptidases on both raw materials. Digesting a spray dried powder derived from the fermenter waste stream of Fusarium venenatum with exopeptidase (1% Flavourzyme TM), resulted in an improved yield of GLN (from 0.1 mg/g to 28.9 mg/g powder) and GLU (from 1.71 mg/g to 5.98 mg/g powder). For milled Alphitobius diaperinus, mixed use of exopeptidase (1% Flavourzyme TM) and endopeptidase (2% Alcalase 1.4-fold increased yield of GLU (17.5 mg/g powder) and 1.7-fold increased yield of GLN (1.2 mg/g) as best production was obtained. For nucleotides, digestions of the waste stream with a yeast lytic enzyme (YL-TLTM) followed by a nuclease (RP-1GTM) resulted in the highest 5’-guanosine monophosphate (GMP) and 5’-adenosine monophosphate (AMP) production. Specifically, a 2% and 0.05% treatment by YL-TLTM and RP-1GTM respectively was shown to be optimal, followed by a 0.05% DeamizymeTM treatment for the conversion of AMP to 5’-Inosinic acid (IMP) of 38 mg/g. For the solid digestion of Alphitobius diaperinus, being treated with a nuclease tretment (2% RP-1GTM) followed by a 0.2% DeamizymeTM treatment for the conversion of AMP to IMP, resulted in the highest GMP yield, a 3.5-fold increased (2.6mg/g), and 7.8-fold increased IMP (4.7mg/g) production.

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40

Tireki, Suzan. "Infrared-assisted Microwave Drying In The Production Of Bread Crumbs". Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/3/12605727/index.pdf.

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This study is aimed to investigate the possibility of using halogen lamp-microwave combination oven for production of bread crumbs and to determine the drying conditions in this oven to produce bread crumbs with the highest quality. Bread crumb dough was dried from about 40.9% to 8% moisture content by conventional oven, microwave, infrared and infrared-assisted microwave drying. In the experiments 30%, 50% and 70% halogen lamp and/or microwave powers were used. As a control, conventional oven drying at 75°
C was used. Conventional drying time was reduced significantly with the usage of infrared, microwave and infrared-assisted microwave drying. Percent reduction in the drying time was found as 96.5-98.6% for microwave, 80.2-94.0% for infrared and 96.8-98.6% for infrared-assisted microwave drying. Contribution of microwave drying was about nine fold of that of infrared drying in infrared-assisted microwave drying. In conventional drying moisture content decayed exponentionally with time whereas in microwave drying it showed a linear decrease. Infrared and infrared-assisted microwave drying fitted the same non-linear model. Total color change values were lower in microwave and higher in infrared drying with respect to the conventional drying. When drying was done by infrared-assisted microwave drying similar color values with the conventionally dried bread crumbs were encountered. Microwave, infrared and infrared-assisted microwave drying methods were effective in increasing water binding capacity. As long as time and energy reduction and high quality were considered, the optimum condition in infrared-assisted microwave drying for production of bread crumbs can be selected as 50% microwave and 30% halogen lamp power.

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41

Arslan, Elif. "Rheological Characterization Of Tahin/pekmez (sesame Paste/concentrated Grape Juice) Blends". Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/1098581/index.pdf.

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The aim of this study was to determine the rheological properties of tahin/pekmez blends at different tahin concentrations (20-32%) and temperatures (35-65 °
C) by using a concentric cylinder rotational viscometer. Samples were sheared with seven different rotational speeds at an increasing order. The shear rates (0.75-63.9 s-1) were calculated by the Power-law Approximation method. Tahin/pekmez blends were found to exhibit non-Newtonian, shear thinning behavior at all temperatures and tahin concentrations. The experimental data of apparent viscosity versus shear rate were successfully described by the Power-law model. The model parameters
flow behavior index, n varied in the range of 0.7-0.85, whereas the values for the consistency coefficient, K, were in the range of 282-2547 mPa.sn. Apparent viscosity and consistency coefficient of blends increased with increasing tahin concentration and decreasing temperature. Temperature dependency of K was described by an Arrhenius-type equation. Activation energies (Ea) of the blends appeared in the range of 13376-28592 J/mol as the tahin concentration was increased from 20% to 32%. The effect of temperature on n was found to be significant but did not follow any descriptive trend. The relationship between K and tahin concentration was explained by exponential and power functions while tahin concentration had no significant effect on flow behavior index. Power function was found to be superior in explaining the variation of Ea with tahin concentration. A mathematical model was formulated to determine the combined effect of temperature, tahin concentration and shear rate on apparent viscosity.

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42

Gezer, Pervin Gizem. "Modeling Drying Kinetics Of Grape Seeds And Skins From Turkish Cultivars". Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613387/index.pdf.

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Grape pomace is a valuable waste product and various end-products have been obtained after treatments. Recently, these have been commercialized due to their health-promoting effects. Drying is a crucial part of these treatments. This study aimed to analyze the drying kinetics of grape pomace parts, which are seeds and skins. Two grape types were used in this study, namely Emir and Bogazkere varieties of Vitis Vinifera species. Seeds and skins of each variety were dried in a tray dryer at an air velocity of 1 m/s with four different air temperatures
40, 50, 55 and 60°
C. The drying curves showed that the drying r ate increased with the air temperature. Six different drying models were selected from the literature and the best fitted model was determined by application of appropriate statistical methods. It was found that for Bogazkere seeds
Modified Two Term Model, for Bogazkere and Emir skins
Modified Page Model and for Emir skins
Logarithmic Model gave the best fit. The effective moisture diffusivities of each type were found for each temperature and were determined by two different approaches, experimental and estimation. The values and variation of Deff / L2 with temperature were calculated and were found to be increasing with temperature and that the Deff / L2 values were larger for grape skins than grape seeds. Arrhenius type equation was used in order to explain the temperature dependency of Deff / L2.

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43

Simsek, Meric. "Microwave Assisted Extraction Of Phenolic Compounds From Tomato And Sour Cherry Pomaces". Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12611896/index.pdf.

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The objective of this study was to compare microwave assisted extraction (MAE) and conventional extraction methods for the extraction of total phenolic compounds (TPC) from tomato and sour cherry pomace. Antiradical efficiency (AE) of the extracts and also the concentration of phenolic compounds were determined. In MAE, the effects of microwave power (400 and 700 W), solvent type (water, ethanol and ethanol-water mixture at 1:1 v/v), extraction time (8-20 min) and solvent to solid ratio (10, 20 and 30 ml/g) were studied to observe the change of TPC and AE of the extracts. Conventional extraction was conducted for 6 h using different solvent to solid ratios (10, 20 and 30 ml/g) and solvent types (water, ethanol and ethanol-water mixture at 1:1 v/v). When the power increased from 400 W to 700 W, TPC and AE values increased. In MAE, maximum TPC and AE values were obtained at a solvent to solid ratio of 20 ml/g. The highest TPC and AE values were obtained when the ethanol-water mixture was used for both MAE and conventional extraction. The highest TPC and AE of tomato pomace extracts was determined as 3.76 mg gallic acid equivalent, GAE/g sample and 4.84 mg 1,1-diphenyl-2-picrylhydrazyl, DPPH/g sample, respectively in MAE using power level of 700 W, ethanol-water mixture, solvent to solid ratio of 20 ml/g and extraction time of 14 min. The major phenolic acids detected in tomato pomace extract were gentisic acid and vannilic acid. For sour cherry pomace extracts, the highest TPC and AE was found as 14.14 mg GAE/g sample and 28.32 mg DPPH/g sample, respectively in MAE using power level of 700 W, solvent to solid ratio of 20 ml/g, ethanol-water mixture and extraction time of 12 min. Epicatechin was found to be the major phenolic acid in sour cherry pomace. There was no significant difference in different extraction methods in terms of TPC. On the other hand, AE value and concentration of major phenolic acids of tomato and sour cherry pomace increased when MAE was used.

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44

Fitriani, Shanti. "Sago starch : behaviour and manufacture of expanded iron-fortified extrudates". Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/38745/.

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Sago starch is extracted from the trunk of sago palm (Metroxylon spp.), which is found throughout South East Asia. In Indonesia sago is considered an underutilised crop and moreover Iron Deficiency Anaemia (IDA) is prevalent among particularly women and children. Creation of a ready to eat product from sago, which was fortified with iron, would address issues of food security both in terms of nutrition and as a non-imported carbohydrate source. With this aim studies for the manufacture of a thermomechanical directly expanded snack product using a commercial source of sago starch were conducted. Composition and properties of sago starch were analysed and compared with rice and cassava. Sago starch differed in several aspects from the two other starches widely processed in Asia. Sago starch had large granules, had the highest amylose levels and gelatinisation temperature (76 °C). X-ray diffraction suggested an A-type packing for all samples, including the sago where literature suggest a C-type ordering. Conversion of the starches (30% moisture) and their flow were studied in a capillary rheometer. A stable extruded product was achieved, but it did not expand. Capillary rheometer data showed pseudoplastic behaviour of the moistened sago starch. With increasing temperature viscosity decreased and no impact of the presence of iron (ferrous sulphate heptahydrate 800 ppm) on the flow behaviour was found, but the inclusion of iron made the extrudates brown in colour. The losses of crystallinity were measured on the extrudates from the rheometer. Levels of order loss were predicted from the state diagram and by comparison with the DSC enthalpy changes for uncooked sago at higher moisture contents. When processed at 70 °C the samples showed more amorphous material than anticipated. When processed at 100 °C still 30% of the order remained. This indicated that shear and moisture levels are critical in the processing of the starch. Thermomechanical extrusion was carried out on a twin screw pilot scale machine (Thermo Fisher, Prism). The screw and die configuration and feed rate for the sago starch (8 kg/h) were fixed. The impact of variable processing parameters of water feed rate (16.5 to 25% wwb), screw speed (200, 300 and 400 rpm) and die temperature (120, 140 and 160 °C) on the physical and physicochemical properties of extruded sago starch were investigated. At the lower water feed rates expansion occurred as the product left the extruder to form a stable extrudate with multiple air cells, which gave a crispy texture. The specific mechanical energies needed to create the expanded product were high at 400-500Whr/kg. The properties of the extrudates were more affected by water feed rate than by alterations in screw speed or die temperature. In order to reduce discolorations, iron-fortified sago starch extrudates were made using iron and ascorbic acid (1:6 ratio). The presence of additives at low water feed rate had no detrimental impact on the extrudates. The recommended extrusion parameters for the manufacture of an extruded sago starch product would be: feed rate of 8 kg/h, screw speed of 300 rpm, die temperature at 140 °C, and water feed rate at 4 mL/min (equivalent to 16.5% wwb), and it is possible that machine settings that produce even higher SME values may allow a more expanded product. From this work it appears that an iron fortified directly expanded sago product could be manufactured. Its nutritional properties and commercial applicability would need to be ascertained.

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45

Mason, C. "Impact of the sensory and postprandial properties of energy drinks on cognition". Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/14459/.

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The impact of energy drinks and their ingredients on cognitive functioning has been of considerable scientific interest in recent years; however studies investigating cognitive effects of energy drink consumption have centred on the postprandial impact, that is the influence of their ingredients once absorbed into the blood. It is possible however, that sensory perception of these drinks, or their ingredients can influence cognition. The four studies outlined in this thesis aim to examine the influences of sensory perception of energy drinks in human volunteers and compare these with the effects observed in the postprandial period on a range of cognitive tasks. Postprandially energy drink treatments were observed to reduce reaction times and improve accuracy compared with a placebo control in a saccadic peripheral conflict task when a 200ms gap was present between a pre-stimulus cue and the stimulus; however when this gap was absent accuracy decreased, suggesting treatment had affected information processing and decision making processes. Sensory perception of a non-carbonated energy drink was observed to improve reaction time and accuracy in a manual choice reaction time task irrespective of gap presence, however an artificially sweetened placebo energy drink had similar effects, but only when the pre-stimulus gap was present. This thesis demonstrates that energy drinks can influence behavioural performance not only by increasing plasma glucose and caffeine levels in the postprandial period, but also through chemosensory perception, an effect elicited by the reward value of taste and flavour perception which is perhaps related to the calorific content of carbohydrates.

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46

Isci, Asli. "Recovery Of Strawberry Aroma Compounds By Pervaporation". Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605084/index.pdf.

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Pervaporation is a selective membrane technique in which a liquid feed mixture is separated by means of partial vaporization through a non-porous perm-selective membrane. This method can be used for the recovery of heat sensitive aroma compounds to avoid them from thermal damage in beverage industries. The main objective of this study was to determine the effects of feed temperature (30, 40, 50°
C), composition (different model solutions, strawberry essence), concentration (50, 100, 150 ppm) and permeate pressure (4, 8 mbar) on the recovery of aroma compounds of strawberry by pervaporation in terms of mass flux and selectivity. In addition, it was aimed to optimize the extraction conditions (extraction time, temperature, agitation speed, strawberry matrix) of Solid-phase microextraction (SPME), which is used for the analysis of strawberry aroma compounds. Optimum results for SPME were obtained at 40°
C, 700 rpm for 30 min and no matrix effect was observed. Pervaporation experiments were performed using a hydrophobic membrane, PERVAP 1070 (PDMS). As the feed temperature increased, the mass flux and selectivity increased and the total mass flux followed an Arrhenius type relation. Decreasing downstream pressure increased both total flux and selectivity, while increase in feed concentration led to higher organic fluxes but lower selectivities. In general, PERVAP 1070 showed a higher selectivity towards Methyl butyrate (MTB) than Ethyl butyrate (ETB) and MTB flux was affected negatively by the presence of ETB in the feed solution. Pervaporation experiments were also performed with a strawberry essence and strawberry model solution. The selectivities of MTB and ETB were negatively affected by the presence of other aroma compounds.

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47

Baltacioglu, Cem. "Production Of Chips And Crisp From Jerusalem Artichoke". Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614084/index.pdf.

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Jerusalem artichoke has been cultivated in various regions without any special breeding technique. On the other hand, in food industry it does not have a wide usage area. Hence, in food industry its use as a potato substitute in some products is believed to be increasing its economical value. As a first attempt chips and crisps produced from Jerusalem artichoke was analyzed for texture, sensory, color, oil and moisture content. Jerusalem artichoke chips were fried in a bench top deep fat fryer for 120s, 180s and 240s at 160°
C, 170°
C, 180°
C and 190°
C. When microwave oven was used samples were cooked for 60s, 75s, 90s, 105s, 120s, 135s and 150s at 600 Watt and 900 Watt. Rheological properties of Jerusalem artichoke puree were investigated and Xanthan gum (2%wb) and sodium metabisulphite (1%wb) added for the desired puree consistence and color. After the production of puree Jerusalem artichoke flour was produced and water added to this flour then dough obtained again. Rheological behaviour of the original puree and these prepared from the containing 1- 4.5 and 1 - 5.0 part water were quite similar. In the light of the experimental results obtained as frying temperature and treatment time increased, moisture content and lightness of the Jerusalem artichoke products have decreased but a*and b* values, hardness, fracture and oil content increased. The best results for frying of Jerusalem artichoke seem to be 180°
C with about 240s treatment time for the chips and the same temperature for 180s for the crisps. As microwave power level and duration of treatment increased, moisture content and lightness of the microwave cooked Jerusalem artichoke products have decreased, but a* and b* values increased. Hardness and fracturability values of the products first increased with time and then decreased. When microwave oven was used, the best results were obtained for about 105s treatment time at 600W for the Jerusalem artichoke chips and about 60s processing time at 900W for the crisp. Since treatment time for cooking was significantly reduced when microwave cooking was used, this method could be recommended as an alternative to conventional deep fat frying, as oil is not used as well.

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48

Can, Cetin Ayca. "Effects Of Edible Chitosan Coating On Quality Parameters Of Pomegranate (punica Granatum) Arils". Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614081/index.pdf.

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The effects of edible chitosan coating on quality factors of pomegranate (Punica granatum) arils were investigated in the present research. For that purpose, pomegranate arils were treated with 0% (control) and 1% chitosan (extracted from shrimp shells and deacetylated (.75%)) solutions and stored at 4

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49

Clark, Rebecca A. "Multimodal flavour perception : the impact of sweetness, bitterness, alcohol content and carbonation level on flavour perception". Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/13432/.

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Flavour perception of food and beverages is a complex multisensory experience involving the gustatory, olfactory, trigeminal, auditory and visual senses. Thus, investigations into multimodal flavour perception require a multidisciplinary design of experiments approach. This research has focussed on beer flavour perception and the fundamental interactions between the main flavour components - sweetness, bitterness (from hop acids), alcohol content and carbonation level. A model beer was developed using representative ingredients which could be manipulated to systematically vary the concentration of the main flavour components in beer and was used in the following experiments. Using a full factorial design, the physical effect of ethanol, C02 and hop acid addition was determined by headspace analysis and in-nose expired breath (in-vivo) measurements. Results from headspace and in-vivo methods differed and highlighted the importance of in-vivo measures when correlating to sensory experience. Ethanol and C02 significantly increased volatile partitioning during model beverage consumption. The effects of ethanol and C02 appeared to be independent and therefore additive, which could account for up to 86% increase in volatile partitioning. This would increase volatile delivery to the olfactory bulb and thus potentially enhance aroma and flavour perception. This was investigated using quantitative descriptive analysis. Results showed that C02 significantly impacted all discriminating attributes, either directly or as a result of complex interactions with other design factors. C02 suppressed the sweetness of dextrose and interacted with hop acids to modify bitterness and tingly perception. Ethanol was the main driver of complexity of flavour and enhanced sweet perception. In a first study of its kind, the impact of C02 on gustatory perception was further investigated using functional magnetic resonance imaging (fMRI) to understand cortical response. In addition, classification of subjects into PROP taster status groups and thermal taster status groups was carried out. Groups were tested for their sensitivity to oral stimuli using sensory techniques and for the first time, cortical response to taste and C02 was investigated between groups using fMRI techniques and behavioural data. There was no correlation between PROP taster status and thermal taster status. PROP taster status groups varied in their cortical response to stimuli with PROP super-tasters showing significantly higher cortical activation to samples than PROP non-tasters. The mechanism for thermal taster status is not currently known but thermal tasters were found to have higher cortical activation in response to the samples. The difference in cortical activation between thermal taster groups was supported by behavioural data as thermal tasters least preferred, but were more able to discriminate the high C02 sample than thermal non-tasters. This research has provided in-depth study into the importance of flavour components in beer. It advances the limited data available on the effects of C02 on sensory perception in a carbonated beverage, providing sound data for the successful development of products with reduced ethanol or C02 levels. The use of functional magnetic resonance imaging has revealed for the first time that oral C02 significantly increases activation in the somatosensory cortex. However, C02 seemed to have a limited impact on activation strength in 'taste' areas, such as the anterior insula. Research comparing data from PROP taster status groups and thermal taster status groups has given insight into the possible mechanisms accounting for differences in oral intensity of stimuli.

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50

Jumel, Kornelia. "Molecular size of interacting and degrading polysaccharides". Thesis, University of Nottingham, 1994. http://eprints.nottingham.ac.uk/11610/.

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The use of multi angle laser light scattering on-line to size exclusion chromatography, analytical ultracentrifugation and viscosity measurements for the determination of molecular weights and conformations of polysaccharide systems is described. The use of several independent techniques for the characterization of polysaccharide systems was found to be essential due to the polydisperse nature of the materials. These techniques were used to investigate the changes in molecular size and conformation of guar gum due to irradiation. Molecular weights and viscosities were found to decrease significantly with increasing radiation dose. Conformational studies on the resulting series of homologous samples confirmed the random coil-like conformation of guar gum. Investigations on BSNdextran complexes, obtained by dry-heating at different molar ratios showed that complex formation (most likely by a Maillard-type reaction) only took place when a low molecular weight dextran fraction was used. The highest molecular weight complexes were obtained when the BSA ratio was high, suggesting that some form of association between individual complexes and/or BSA had taken place.

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