Dissertations / Theses on the topic 'Bread flour quality testing'

Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2009.
Endoxylanases are known to improve dough stability, oven spring, loaf volume, crumb structure and shelf life. The use of endoglucanases (cellulases) usually results in increased bread loaf volume, bread score and reduced crumb firmness. Even though bakeries use ‘pure’ enzymes in their formulations, they are supplied with an enzyme mixture which can contain up to five different enzymes. These mixtures often also include an emulsifier and ascorbic acid. To compare the ability of endoxylanase and endoglucanase to improve bread quality characteristics, a commercial endoxylanase (from Aspergillus niger) and endoglucanase (from Trichoderma reseei) were evaluated together with a pure endoxylanase and endoglucanase (both from Trichoderma sp). Baking trials were conducted on small (100 g) as well as commercial (700 g) scale. Quality characteristics evaluated included dough quality, bread weight, bread height, bread volume, softness of crumb, bread slice characteristics and overall crumb texture. All the results were compared to a control. From the results of the small-scale baking trials both the pure and commercial endoxylanases significantly (P<0.05) improved bread height and softness of crumb, with the pure endoxylanase also increasing slice brightness. Both the pure and commercial endoglucanases significantly (P<0.05) increased softness of the crumb and slice brightness. When the enzymes were evaluated in combination, only an increase in bread height was observed for some of the combinations. From the results of the baking trials conducted on commercial scale, the loaf height was significantly (P<0.05) increased by the pure endoxylanase and the pure endoglucanase, while the bread volume was significantly (P<0.05) increased by all the enzymes being tested. Enzyme combinations resulted only in a significant (P<0.05) increase in bread volume. The texture of the bread crumb was significantly (P<0.05) influenced by the commercial endoxylanase, the pure endoxylanase, the pure endoglucanase as well as two of the enzyme combinations, resulting in a more open and coarse crumb texture. Slice brightness was significantly (P<0.05) decreased by the commercial endoxylanase, the pure endoxylanase, the pure endoglucanase as well as the two enzyme combinations. Both endoxylanases and endoglucanases can therefore be used to improve bread quality characteristics such as bread height and/or volume, slice brightness and softness of crumb. However, using pure enzymes specific characteristics can be targeted. This would become more feasible if pure or single component enzymes become more readily available and cost effective to use. Apart from testing the effect of the enzymes on bread quality characteristics using small-scale baking trials, it was shown in this study that testing of enzymes could also be efficiently conducted on commercial scale. In the latter the enzymes were being tested using commercial white bread flour as well as a leaner formulation. The leaner formulation allowed for the effect of the enzymes to be observed more prominently. The benefit of the evaluation on commercial scale was that the effect of the enzymes was tested in a process similar to that used in industry.

The effects of variation in nitrogen application during two growing seasons to Coker 916, a soft red winter wheat, on wheat grain and flour protein content and bread baking properties were examined. Nitrogen fertilization regimens tested included the single spring application of 168 kg/ha in growth stages 25 or 30, the split spring application of 224 kg/ha in growth stages 25 and 30, and no nitrogen application either in growth stages 25 and 30. Variation in rate of nitrogen application had a more consistent effect on grain and flour protein than did variation in timing. Grain and flour protein content increased with increased nitrogen fertilization. The gliadin to glutenin protein ratio of the flour was reduced as the rate of grain nitrogen application increased. Significant differences were found in the flour gliadin percent protein with variation in spring nitrogen management. Fractionation and resolution of gliadin and glutenin components using SDS-PAGE revealed changes in the relative quantities present of two high molecular weight glutenin subunits (108,000 and 91,000 daltons), one low molecular weight glutenin subunit (40,500 daltons) and the ω-gliadin (44,000 daltons) fraction of experimental flours. Differences in dough rheological properties and baking characteristics of the flour were associated with variation in nitrogen management. Increased nitrogen fertilization resulted in a stronger, more extensible dough with improved mixing tolerance and dough handling characteristics. Increased flour protein was associated with larger bread loaf volume and darker crust color. Sensory panelists found significant differences in the bread crust color, texture and taste, bread aroma, crumb texture and chewiness. This experiment demonstrated that a change in nitrogen management of Coker 916 wheat resulted in a distinct change in protein composition and bread baking properties of experimentally milled flour.
Ph. D.

Master of Science
Food Science Institute
Fadi Aramouni
Flour from the fruit of breadfruit trees (Artocarpus altilis) holds the potential to serve as an alternative to gluten-containing flour and may aid in alleviating food insecurity. This study assessed the effects breadfruit flour contributes to gluten-free bread quality. Breadfruit flour was included at a baker’s percentage (0, 20, 35, 50%) of a gluten-free flour blend, and was treated with various leavening agents (yeast, 15% baking powder, 20% baking powder) to create varying gluten-free bread formulas. Density and pH of each batter was assessed along with loaf density, yield, specific volume, pH, water activity, crust color (L*, a*, b*), crumb color (L*, a*, b*), and texture. Additionally, a consumer sensory study was performed to ascertain degree of liking of appearance, color, flavor, texture, aftertaste, likelihood to purchase, and overall acceptability. Significant differences (p < 0.05) were found in batter pH, loaf density, yield, specific volume, color (crust b*, crumb L*, a*, b*), pH, water activity, and texture among flour inclusion and leavening treatments. Consumer testing yielded significant differences (p < 0.05) between the control and a yeast leavened 20% breadfruit formula in appearance, color, flavor, aftertaste, likelihood to purchase, and overall acceptability. While most consumers rated the breadfruit treatment lower than the control, five celiac panelists rated it higher. Among all treatments, loaves produced from 20% breadfruit flour inclusion had significantly lower density, yield, hardness, adhesiveness, gumminess, chewiness, and crumb yellowness (b*), as well as higher specific volume, springiness, crust yellowness (b*) and darkness (L*), crumb darkness (L*), and magenta hue (a*) compared to other breadfruit flour inclusion levels. Similarly, loaves leavened with yeast had significantly lower batter pH, loaf pH, density, yield, hardness, chewiness, crust yellowness (a*), crumb darkness (L*), magenta hue (a*), and yellowness (b*) as well as higher loaf water activity, volume, springiness, and crust darkness (L*) compared to other breadfruit flour inclusion levels. These results indicate breadfruit flour can be used at ≤ 20% in gluten-free bread formulas to replace rice flour and has potential as a fiber supplement. Further research is needed to assess how breadfruit flour affects the quality of other gluten-free product formulas.

The goal of this research is to determine the effects of added soybean lipoxygenase (LOX) on bread dough rheological properties and physical properties of bread loaves compared to controls, and to determine sensory attributes of bread loaves using quantitative descriptive analysis (QDA). Protein fractions were obtained through the use of isoelectric precipitation. The pH 4.8 precipitate was found to yield the greatest LOX activity when compared with other fractions (p<0.05). The addition of pH 4.8 precipitate improved rheological properties of bread dough, examined in a farinograph, when compared to the all-purpose control (p<0.05). Addition of soy flour also increased the gluten strength of all-purpose flour (p<0.05). The addition of pH 4.8 precipitate to all-purpose flour did not improve bread loaf volume or texture. Sensory panelists described pH 4.8 supplemented bread as having firmer crumb when compared with controls (p<0.05). There were slight color differences among the loaves. The crust and crumb of bread flour loaves was lighter in color than any other sample. It was concluded that the addition of pH 4.8 precipitate to all-purpose flour greatly improved the rheological properties when compared with all-purpose flour alone.
Master of Science

The purpose of this research was to examine the relationship of the protein and lipid content of soft wheat flour to baking quality and their changes as a result of chlorination. Coker 916, soft red winter wheat, was grown under different fertilization treatments involving rate and application time to alter protein content. One-half of all flour treatments were subjected to chlorination. The lipid and protein content, gliadin and glutenin composition, microstructure, rheological properties, ash, pH and color were examined. Baked angel food cakes were evaluated by volume, tenderness, color, cohesiveness, crumb structure and microstructure (SEM). Gelatinization temperatures of batters were measured by Differential Scanning Calorimetry (DSC). Sensory analysis was judged by quantitative descriptive analysis (QDA). Increased levels of fertilization of the grain increased the protein content (8-11%) of the flour. Cakes from flours of Increased protein content were significantly lower in volume than cakes of flours of lower protein content. Chlorination decreased protein content in flour which affected the glutenin composition in some flours. Gliadin content remained unchanged. Doughs of chlorinated flours were significantly less stable as measured by mixing time stability and mixing time index. Chlorination decreased the unsaturated fatty acid methyl esters (FAME). There was strong correlation between evenness of cell structure and the decrease of fatty acids 18:1, 18:2, and 18:3 with chlorination. Phospholipids which were qualitatively evaluated were implicated with cell evenness. Cakes of chlorinated flours were significantly less in volume and tenderness, but the structure showed complete starch gelatinization, increased whiteness and cell evenness. Sensory data correlated significantly with objective data. Chlorination of flour stabilized the structure of the baked product. Low protein and decreased FAME content improved the baking properties of the flour. Flours of lower protein and a lower lipid content that are chlorinated are recommended for baked products such as cakes and biscuits.
Ph. D.

All-purpose wheat flour is a useful long-term storage commodity, but is subject to off-odor formation. Although flour stored in a low oxygen atmosphere should inhibit rancid odor formation, it elicits consumer complaints about odor. The purpose of this study was to examine off-odor development in all-purpose wheat flour during ambient and elevated storage by determining the effect of low oxygen atmosphere and enrichment-bleaching on quality as measured by, free fatty acids (FFA), flour descriptive sensory analysis, conjugated dienes, headspace volatiles, bread consumer sensory analysis, color, loaf volume, and vitamin analysis. Enriched, bleached (EB) and unenriched, unbleached (UU) flour was stored in a low and normal oxygen atmosphere in no. 10 cans at 22, 30, and 40°C for 24 weeks. Moisture remained constant throughout the study. Headspace oxygen was < 0.1% in flour stored in a low oxygen atmosphere and decreased in flour stored in a normal oxygen atmosphere. FFA increased with storage time and temperature. The "fresh flour" descriptive aroma of flour decreased during storage and decreased more rapidly in a low oxygen atmosphere. The "cardboard/stale" aroma increased in flour stored in a normal oxygen atmosphere. The "acid-metallic" aroma increased in flour stored in a low oxygen atmosphere and was determined to be the off-odor from consumer complaints. Conjugated dienes and volatiles generally increased more rapidly in flour stored in a normal oxygen atmosphere and in EB flour, suggesting that the acid-metallic odor did not result from lipid oxidation. Bread consumer sensory analysis identified EB flour stored in a normal oxygen atmosphere to have the lowest acceptance scores for aroma, overall acceptability, and flavor. The acid-metallic odor dissipated within 24 hours when the container was opened and was not detrimental to consumer acceptance of bread made from the flour. Oxygen absorbers prevented the darkening of flour but not the reddening or yellowing. A low oxygen atmosphere resulted in higher bread loaf volumes. Vitamin degradation is not a concern under normal storage conditions. Bleaching appears to increase flour oxidative rancidity more than enrichment. Although storage at a low oxygen atmosphere results in an off-odor present in newly opened cans, it gave higher quality flour and bread. A low oxygen atmosphere should continue to be used in flour stored long-term, and consumers should be made aware that the off-odor present in cans of flour dissipates after opening.

Uprkos brojnim tradicionalnim reološkim metodama koje se već dugi niz godina koriste u proceni kvaliteta brašna, postoji potreba za razvijanjem novih metoda, pomoću kojih bi se za kratko vreme i uz ograničenu količinu uzorka mogao uspešno predvideti kvalitet brašna i gotovog proizvoda. Na taj način selekcionerima bi bila omogućena procena tehnološkog kvaliteta linija pšenice čija je količina ograničena, dok bi se mlinarima obezbedio brz metod procene kvaliteta. Osnovni cilj istraživanja ove disertacije je ispitivanje mogućnosti primene novog reološkog uređaja glutopika u proceni kvaliteta brašna i finalnog proizvoda – hleba, kao i mogućnost zamene tradicionalnih dugotrajnih metoda novom reološkom metodom.Kako bi se ispitale i iskoristile mogućnosti reološkog uređaja glutopik za procenu kvaliteta pšeničnog brašna definisani su optimalni uslovi merenja koji su podrazumevali upotrebu NaCl kao rastvarača i zadate parametre temperature (36 °C), obrtne brzine mešača (2700 rpm) i odnos brašna i rastvarača (8,5/9,5). Zabeležen je veliki broj korelacija između parametara glutopika i empirijskih reoloških pokazatelja kvaliteta brašna i testa. Takođe je utvrđena značajna korelacija između parametara glutopika i indikatora kvaliteta hleba u pogledu specifične zapremine i teksturnih karakteristika sredine hleba. Na osnovu parametara dobijenih merenjem na glutopiku definisane su granične vrednosti. Ustanovljeno je da se primenom glutopik metode može izvršiti klasifikacija sorti pšenice prema kvalitetu. Pored toga, utvrđeno je da glutopik ima veliki potencijal da zameni alveograf u proceni kvaliteta brašna u mlinarskoj i pekarskoj industriji. Reološki parametri koji zavise od sadržaja proteina kao što su moć upijanja vode i žilavost testa uspešno se mogu predvideti pomoću parametara glutopika. Primenom glutopik metode postignuta je umerena predikcija specifične zapremine hleba, dok je postignuta veoma dobra predikcija teksturnih karakteristika sredine hleba.U okviru ove disertacije je ispitan uticaj sorte i lokaliteta na tehnološki kvalitet brašna pšenice kako bi se utvrdilo koja od ispitivanih sorti ispoljava ujednačen kvalitet u različitim mikroklimatskim uslovima tokom dve proizvodne godine. U obe proizvodne godine pokazatelji kvaliteta brašna su dominantno sortno određeni, pri čemu je zabeležen određeni uticaj mikroklimatskih faktora na lokalitetima gajenja. Odličan i najstabilniji kvalitet brašna u 2011. godini je imala sorta Gordana koja je pokazala najveću adaptabilnost na mikroklimatske uslove. Apač je uniformno imao najlošiji kvalitet duž svih ispitivanih lokaliteta. Domaće sorte su u 2012. godini imale promenljiv kvalitet u zavisnosti od lokaliteta gajenja. Hlebove proizvedene od domaćih pšeničnih sorti je karakterisala velika zapremina, rastresita struktura sredine sa izraženim velikim porama i mala čvrstoća sredine, dok je hleb proizveden od sorte Apač imao malu zapreminu, zbijenu strukturu sredine hleba sa velikim brojem malih pora kao posledicu velike čvrstoće. Dobra predikcija kvaliteta hleba od brašna iz 2011. godine je postignuta primenom jednog reološkog pokazatelja kvaliteta, dok je za uspešnu predikciju kvaliteta hleba od brašna iz 2012. godine neophodno izvesti nekoliko različitih reoloških merenja.Analizom tehnološkog kvaliteta brašna pšenice različitih sorti gajenih na različitim lokalitetima iz tri proizvodne godine zabeležene su velike varijacije u kvalitetu brašna i hleba na ispitivanim lokalitetima i u proizvodnim godinama, što jasno ukazuje na značajan uticaj interakcija između sortimenta i uslova gajenja (lokaliteta i godina), kao i značaj ispitivanja ovih interakcija i razvoja strategija koje imaju za cilj smanjenje uticaja spoljašnjih faktora na kvalitet pšenice.
Regardless the fact that numerous traditional rheological methods have been used for many years in the flour quality assessment, there is a need for developing new methods, which could, in a short time, and with a limited amount of sample, successfully predict the quality of flour and finished products. In this way, wheat breeders would be able to evaluate the technological quality of the wheat lines with a restricted sample quantity, while the millers would be provided with a quick method of the quality evaluation. The main goal of the research of this dissertation was to examine the possibility of using a new rheological device GlutoPeak in the quality evaluation of flour and final product – bread, as well as the possibility of replacing traditional time-consuming methods with a new rheological test.In order to examine the possibility of using a GlutoPeak rheological device for the flour quality evaluation, the optimal measurement conditions were defined and included the use of NaCl as a solvent, the rotational speed of the mixer (2700 rpm), temperature (36 °C), the ratio of flour and solvent (8.5/9.5). Numerous correlations between GlutoPeak indices and empirical rheological parameters of dough behaviour were reported in this study. Significant correations were also observed between GlutoPeak parameters and bread specific volume and breadcrumb textural properties. The limit values were defined according to the GlutoPeak parameters values. Moreover, it was found that the GlutoPeak test could be used for wheat variety diferentiation according to the quality and has a great potential to replace Alveograph in the flour quality assessment in the milling and bakery industries. Parameters which depends on the protein content, such as, flour water absorption and dough tenacity, was successfully predicted by using parameters derived from GlutoPeak tester. A moderate prediction of loaf specific volume was achieved, while a very good prediction of breadcrumb textural characteristics was accomplished with the GlutoPeak parameters.In addition, the influence of genotype and growing location on flour quality was examined in order to determine which of the tested varieties exhibited uniform quality accross different microclimatic conditions in two production years. It was revealed that in both production years flour quality indicators were predominantly influenced by genotype, with a certain influence of microclimate factors on the growing locations. Gordana variety showed excellent and uniform quality with the highest adaptability to microclimate conditions in year 2011. Apache variety showed uniformly poor quality across all tested locations. In year 2012 domestic varieties exhibited variable quality depending on the growing locations. Bread produced from domestic wheat varieties was characterized by a large volume, loose breadcrumb structure with pronounced large pores and low hardness, while the bread produced from Apache variety had a small volume, dense breadcrumb structure with a large number of small pores as a result of high breadcrumb hardness. The quality of bread produced from wheat flour from year 2011 was well predicted based on one rheological quality parameter. On the other hand, several different rheological measurements was performed to successfully predict the quality of bread produced from wheat flour from 2012 year.By analyzing the technological quality of wheat flour of different varieties cultivated at different locations from three production years, large variations in the quality of flour and bread was recorded. The variations in flour and bread quality indicated the significant influence of interactions between the variety and growing conditions (locations and years), as well as the importance of examining these interactions and developing strategies aimed at reducing the impact of external factors on wheat quality.

Thesis (M.Sc. (Agronomy)) --University of Limpopo, 2013
In South Africa, wheat ranks first among the winter cereal crops produced and plays an important role in the country’s economy. The study was conducted to evaluate different South African wheat cultivars under irrigation for quality and yield parameters in Limpopo province. A field experiment was conducted during 2011 winter growing season under irrigation at the University of Limpopo experimental farm (Syferkuil). Eight wheat cultivars namely: Olifants, CNR 826, SST 347, Baviaans, Duzi, Steenbrass, SST 356 and Krokodil were laid out in a randomized complete block design with four replications for evaluation of yield and quality. The results showed that the highest grain yield obtained was 2372 kg/ha by CNR 826, and the lowest 311 kg/ha by SST 347. Flour yield, break flour yield, flour protein and mixogram development time and water absorption were not significantly different among cultivars. The highest hectolitre mass was 75.13 kghl-1for CNR 826 and the lowest 72.20 kghl-1 for Olifants. The highest falling number obtained was 187.00 sec for SST 347 and the lowest was 81.50 sec for Steenbrass. Cultivars CNR 826, SST 347, Steenbrass and SST 356 showed a good potential on protein content but Krokodil, Olifants and Baviaans had poor protein contents at 9.63%, 9.73% and 10.24% respectively. These results showed that wheat cultivars evaluated were within the requirements of the grading systems of South Africa as regards hectolitre mass and protein content. All these cultivars did not reach the required grade of 220 seconds in falling numbers with Olifants (97.50 sec), CNR 826 (103.50 sec), SST 347 (187.00 sec), Baviaans (146.75 sec), Krokodil (139.50 sec), Steenbrass (81.50 sec) and Duzi (50.25 sec), but only SST 356 met the requirement for utility grade with164.50 seconds. Olifants, CNR 826, Krokodil and Steenbrass yielded above 1500 kgha-1thus showing good potential under Limpopo conditions. These cultivars could be included in future performance evaluations in Limpopo.

Although less common in human food, studies have reported the beneficial effects of b-glucans present in the soluble portion of barley dietary fiber, such as implications in serum cholesterol and blood glucose reduction, besides anticarcinogenic properties. Barley is not commonly used in bakery products, however, partial replacement of wheat flour with barley can result in the development of acceptable and functional products, coming as alternative of bread enrichment. This study aimed to evaluate the technological viability of the incorporation of barley, in the form of flour, on the quality parameters of bread to make a choice of food with potential health benefits to the consumer. Barley flour (BF), whole barley flour (WBF), and breads produced with these flours were characterized as for chemical composition and physical properties. Flours were also analyzed for the granulometry and rheological properties, while the loaves were evaluated as for the quality parameters and sensory analysis. The addition of barley flour in bread did not interfere in nutrient composition and resulted in a favorable increase in fiber levels and dough water capacity absorption. Levels of substitution of up to 30% of barley flour and 10% of whole barley flour did not affect bread softness. As far as barley substitution level increased, texture increase and bread volume decrease were observed. Thirty porcent substitution level of BF and WBF showed desirable bread quality and all breads produced were accepted by consumers, indicating possibility of being produced and subsequently comercialized.
Embora pouco utilizada na alimentação humana, estudos têm relatado os efeitos benéficos das betaglucanas presentes na porção solúvel da fibra alimentar da cevada, tais como implicações sobre o colesterol sérico e redução da glicose sanguínea, além de propriedades anticarcinogênicas. A cevada não é comumente usada em produtos de panificação, entretanto, substituição parcial de trigo com a farinha de cevada pode resultar no desenvolvimento de produtos aceitáveis e funcionais, surgindo como uma alternativa para o enriquecimento de pães. Este trabalho teve como objetivo avaliar a viabilidade tecnológica da incorporação da cevada, sob a forma de farinha, sobre os parâmetros de qualidade do pão de forma a fim de disponibilizar uma opção de alimento com possíveis benefícios à saúde do consumidor. As farinhas de cevada (FC) e de cevada integral (FCI), e os pães elaborados com estas farinhas, foram caracterizados quanto à composição química e propriedades físicas. As farinhas foram ainda analisadas quanto à granulometria e as propriedades reológicas, enquanto os pães foram avaliados quanto aos parâmetros de qualidade e análise sensorial. A adição de farinha de cevada no pão de forma não prejudicou a composição de nutrientes e resultou em um aumento favorável nos teores de fibras e da capacidade de absorção de água na massa. Níveis de substituição de até 30% de farinha de cevada e 10% de farinha de cevada integral não afetaram a maciez dos pães. À medida que aumentaram os níveis de substituição de trigo por cevada, observou-se aumento na firmeza e diminuição do volume dos pães. Níveis de substituição de até 30% de FC e FCI produziram pães com qualidade desejável e todos os pães elaborados foram aceitos pelos consumidores, indicando possibilidade de serem produzidos e posteriormente comercializados.

Bread flour quality, which is directly related bread quality, varies from time to time. It is therefore almost impossible to obtain bread with consistent quality without determining the flour's suitability for bread-making and the addition of bread improvers. Rheological tests such as the farinograph and the mixograph which are commonly used by bakeries to predict flour quality are empirical in nature which makes fundamental interpretation of the results difficult. The stress relaxation test, a more fundamental rheological test, was used in combination with the mixograph to determine if the stress relaxation test can provide additional information to the mixograph on prediction of the effect of ascorbic acid and DATEM on bread-making quality of three different flour samples. In this test, an optimally developed ball of dough was compressed between parallel plates of a TA-XT2 texture analyser. The 20 g dough was compressed to a load of 1.5 N and thereafter allowed to relax at constant deformation. The relaxation time (RT) was recorded as time taken for the compression force to decay to a force of 0.65 N. Longer RT indicated better flour quality. RT was compared with the mixograph peak time and peak height as predictors of the effect of ascorbic acid and DATEM on bread quality. Test bakes were carried out, and concentrations of ascorbic acid and DATEM were varied as in the stress relaxation test and the mixograph test. At the various stages of the baking process several dough and bread properties were assessed subjectively and scored according to a standardised scoring system. The mixograph was successful in characterising untreated flours in terms of bread-making quality and the stress relaxation test did not provide additional information in this regard. The mixograph was better able to predict the effect of improvers on the stronger Lelie while the stress relaxation test was better at predicting improver effect (especially of DATEM) on the weaker flours, Tiger and Silver Queen. The mixograph predicted the improving effect of DATEM on Tiger and Silver Queen up to a peak, followed by no further improvement. The stress relaxation test predicted improvement beyond the peak, and this continued improvement was observed in the test bake and strong correlation (pDissertation (MSc (Agric) Food Science and Technology)--University of Pretoria, 2005.
Food Science
unrestricted

碩士
國立臺灣大學
農業化學研究所
96
The purpose of this study was to investigate the physicochemical and baking properties of wheat flours obtained from 4 commercial French bread specialty flours (flour A, B, C, and D) and 3 flours blended from flour streams (flour H, M, and L). The results showed that the protein, wet gluten and F1* content, %UPP, Extensograph R value were higher in flour A and B than flour C and D. Breads made from flour A and B had higher specific volume and form ratio than those made from flour C and D. Among four commercial flours, flour D was unique in its high gluten index but low protein content. This was attributed to its high ratio of high molecular weight glutenin (F1* and F1). The unique protein quality of flour D contributed to the high P and W values of SMS D/R inflation test. This characteristic also reflected to the good specific volume and form ratio of bread made by long proofing time. The round hearth bread made form flour A and Baguette made from flour D had the highest scores in overall acceptance of sensory evaluation. The three flours obtained from stream-blended flours were significant different in their ash and protein contents. Flour H had high ash, protein and wet gluten content with low %UPP, less resistant and dough stability and short developing time. The breads made by long proofing time (> 60 min) had low volume and small form ratio. On the contrary, flour L contained low ash, protein and wet gluten, but high gluten index, %UPP, Farinograph and R valure. The flour L had long developing time and good dough stability, however, the breads made from this flour was small in volume and high in form ratio and hard in texture. The long proofing time (> 90 min) was required for improving the bread volume and texture made from flour L. Flour M owned the properties between flour L and H and had the similar chemical composition (wet gluten content, gluten index and %UPP), dough property (dough stability) and bread quality (form ratio) with flour A. According to the results in this study, the gluten index, F1*, F1 and %UPP values could be used as the protein quality index of wheat flour for hearth bread and French bread mainly.

碩士
國立臺灣大學
農業化學研究所
92
There are two major parts of this study. In the first part, the composite flour, a mixture of waxy rice flour and wheat flour was used for steam bread making and the effects of waxy rice flour on the properties of dough and steam bread were investigated. In the second part, some wheat flour was pregelatinized before the sponge dough prepared and the effect on pregelatinized wheat flour on the properties of dough and steam bread were investigated. The amounts of wheat flour substituted by waxy rice flour in the composite flour and the ratio of pregelatinized wheat flour used were 10%、20% and 30%. The substitution of waxy rice flour in composite flour reduced in reducing its amylose content, and diluting its gluten content. The changes of pasting and gluten properties of dough, which was prepared with some of pregelatinized wheat flour, were observed. The changes of compositions of flour and pregelatinization treatment resulted in the significant changes of extensibility of dough, furthermore, the appearance and storage quality of steam bread was undesirable. The optimal formulations were able to produce the good appearance and storage quality of steam bread by adjusting the water absorption and vital gluten addition according to the results of the RSM experimental design. The steam breads made by the optimal formulations were then stored under three conditions (i.e. room temperature, refrigeration and freeze-thaw cycle) and the moisture content, hardness and enthalpy of steam bread crumb were determined during the storage periods. The results showed that the hardness of steam bread increased with increasing storage time in all three storage conditions, but with different rates. The moisture content of steam breads were different because the formulations but the moisture content did not change in each steam bread during storage. The retrogradation rate of starch was influenced by the formulation and storage condition. That is, the steam bread made with high water absorption was soft at fresh, but the degree of retrogradation during storage varied after storage. The steam bread made with 20% or 30% pregelatinized wheat flour before sponge preparation, no starch retrogradation was observed by the DSC determination although the hardness of crumb increased under the storage at room temperature. The steam bread made with the optimal formulations for composite flour (wheat:waxy rice＝8:2) and 20% pregelatinized wheat flour had the great acceptability when evaluated by sensory tests. The steam bread made with composite flour (wheat:waxy rice＝8:2) maintained the softer crumb texture after 1 day storage at room temperature than the steam bread made with 100% wheat flour. Such conclusion can be made that the proper adjustments of formulation is the requirements to make good appearance, eating and storage qualities of steam bread when waxy rice flour or pregelatinized wheat flour was applied. The waxy rice flour and pregelatinized wheat flour did improve the storage quality of steam bread stored at room temperature, which was attributed majority to the high moisture content of steam bread and/or to the weak starch gelation strength due to reduce the amylose content in composite flour.

碩士
中國文化大學
生活應用科學研究所
97
The purpose of this research was to grind six-row barley to whole barley flour (SRB-PF) and albumen (SRB-EF). Mixture of Variable percentage of SRB-PF/SRB-EF and all-purpose wheat flour were used to make steamed breads according to a standardized procedure. We use the Rapid Visco Analyzer（RVA）, Farinograph, Extensograph, Glutomatic to analyze the physical characteristics of barley dough. Color, texture, store quality and sensory evaluation of steamed barley breads were also evaluated. The soluble fiber（β-glucan）with in the barley steamed breads were cooked to determine the stability during heating process. The research results showed that SRB-PF were more abundant in dietary fibers and β-glucan than SRB-EF. The β-glucan retained high stability in the steamed barley breads when heated up to 120~130℃. Paste viscosity, the set back viscosity （SB）and final viscosity （F） of barley flours are higher than all-purpose wheat flours. Break-down viscosity （BD）and set back viscosity（SB）rose when percentage of SRB-EF increased. The overall pasting temperature was between 62-63℃. Gluten content and water-holding capacity decreased when more percentage of SRB-PF increased. Farinograph examination disclosed that departure time（DT）and stability（ST）decreased value but mixing tolerance index （M.T.I.） rose while more percentage of SRB-PF increased. The SRB-PF dough had weak gluten than SRB-EF dough. Extensibility（E value）and area （A value）decreased value but R/E ratio and resistance to extension （R value）rose value when using more percentage of SRB-PF. In the mixed barley dough, gluten increased with time but barley dough decreased fermentation ability. In the SRB-PF and SRB-EF steamed breads, specific volume, lightness（L value）and white index（WI）decreased trend while percentage of barley flours increased. The specific volume value between 2.43-3.74 （㏄ / g）. SRB-PF and SRB-EF steamed breads were harder and more chewable while more barley flours were used and storage time increased. The sensory evaluation score of SRB-PF steamed breads were lowest while more percentage of SRB-PF was used in steamed breads. However, the sensory evaluation score of SRB-EF and control（all-purpose wheat flour breads）were not significantly different.

碩士
中國文化大學
生活應用科學研究所碩士在職專班
91
Steamed bread is a representative of the Chinese flour food culture. As a food product, it is compatible to bread in the West. But as compared with the bread, regarding specifically the theoretical foundation of its production process, there are stillrooms for further exploration. Therefore, this project is designed to utilize the multiple stages ingredient mixing method used in the flourmills to first produce three kinds of wheat flour containing 10 percent and 12 percent protein content respectively. For each king of wheat flour with a specified protein content adding R/E with different values at 2, 4, 8 and 3, 7, 10 respectively produces another three kinds. After completion of this mixing process, a total number of six different kinds of wheat flour with varying degrees in the protein quantity and quality are produced; steamed breads are made through standardized formula and production process. The steamed breads are then measured based on its color, volume, Texture. It was found that the steamed bread preparing from the higher protein content wheat flour, the specific volume was higher, the different quality wheat flour were similar in colorness, and the hardness of steamed bread was the lowest in the 12% protein content and R/E value is 10, and the hardness of steamed bread was the highest in the 10% protein content and R/E value is 4. Correlation Analysis of physical properties indicate that positive correlation between volume、specific volume of steamed bread and R/E value symmetry of steamed bread and E value negative correlation between symmetry of steamed bread and R value.

碩士
國立臺灣大學
食品科技研究所
105
Celiac disease (CD) is an autoimmune disease with an estimated prevalence of about 1%. It is caused by the ingestion of wheat gluten, as well as proteins in related cereals, such as wheat, barley, rye, and possibly oats. In recent years，there has been growing interest in gluten-free products. Because of the link between Type 1 diabetes and celiac disease was established and the glycemic index of most gluten-free foods are high. Resistant starch enrichment is added into gluten-free food to induce glycemic response, which is highly desirable for individuals with concomitant CD and type 1 diabetes. Banana flour (BF) was obtained from unripe banana that rich in resistant starch. Particle size related to the surface area available for enzymatic action, and thus affects the enzymatic digestion starch. The purpose of this study is to understand the influence of the banana flour particle size (<75 μm，75∼106 μm，106∼180 μm) on quality and digestibility of gluten-free banana bread. Experiment design employed response surface methodology (RSM). Using specific volume of bread as evaluation index, and the optimum formula were obtained as follows: banana flours 22.74 g，water 98.78 g，三仙膠 6.19 g. Under the optimized conditions, it can be included that the average specific volume was 3.23 m3/kg, which is close the estimated value 3.25 m3/kg.Different flour properties effect on quality and digestibility of gluten-free banana bread. The coarse banana flour lead to lower GI (glycemic index) of gluten-free banana bread. The coarsest flours produce breads with a lower specific volume, more dark color and harder crumb. In the sensory evaluation, the coares flours obtained higher score. Thus, adding coarse banana flour into gluten-free bread can inherent quality if more water is added.

Due to the high cost of wheat importation in countries where the climatic conditions do not favour its cultivation, alternative sources of bread baking flour are required. Maize is a suitable alternative because it is by far the most important crop produced in Africa. However, it lacks gluten, the protein that is formed in wheat dough which is responsible for the desirable quality attributes (high loaf volume, soft and open crumb structure) of wheat bread. Therefore the need arises to improve maize bread quality. The effects of three types of non-wheat bread methods on the quality of maize bread were investigated. The first was a traditional sourdough method used in Lesotho for making steamed bread. This involved addition of spontaneously fermenting sorghum malt sourdough (equivalent to 15% of the total maize flour) and pre-gelatinization of the starch in the maize flour with boiling water. The second was a Food and Agriculture Organization method which involved pre-gelatinization of the starch in 10% of the maize flour by cooking. The third method was a modern gluten-free sourdough method which involved fermenting 75% of the maize flour with a multiple strains starter culture or Lactobacillus plantarum plus the natural flora in the maize. The modern sourdough method produced maize bread with a more open crumb structure and a significant increase in loaf volume compared to the other methods. This was probably related to the high percentage of fermented maize flour in the recipe, which was probably sufficient to modify the dough properties satisfactorily enough to impact positively on the maize bread quality. Based on these findings, the modern sourdough method was investigated further. Maize sourdoughs were prepared (as described) and compared to chemically acidified maize dough. Sourdough maize bread had an approx. 25-26% increase in loaf volume and a more open crumb structure with large gas cells. This showed that the maize bread quality improvement was not due to low pH. Confocal laser scanning microscopy revealed a cohesive dough structure in the sourdoughs. Larger cells and a more uniform crumb structure were also observed in maize breads with maize sourdough. This indicated an improvement in the maize dough properties with sourdough. Differential scanning calorimetry showed that maize sourdough had a slightly lower peak temperature than straight maize dough, an indication of starch modification. Rheological analysis showed that maize sourdough had a shorter relaxation time, an indication that it was less elastic. Strain sweep analysis revealed that maize sourdoughs had the lowest elastic modulus, also indicating a less elastic dough. Temperature sweep analysis showed an initial less elastic dough and a final high tan delta, suggesting that the maize dough could withstand gas expansion pressure during baking without crumbling. The dominant lactic acid bacteria in the sourdoughs were identified as L. plantarum. In the two sourdoughs, the L. plantarum present were gram-positive, catalase negative and exhibited proteolytic activities. However, only the L. plantarum in the multiple strains starter culture fermented maize sourdough exhibited amylolytic activities. It is proposed that proteolytic activity of the L. plantarum degraded the endosperm protein matrix and hydrolysed the proteins soluble in the dough liquid, thereby allowing increased accessibility of water to the starch granules. It is further proposed that the amylolytic activity of the L. plantarum slightly hydrolysed the starch granules, increasing water absorption by the starch granules. It is proposed that improvement in maize bread quality by sourdough fermentation is due to starch modification (increase water accessibility and water absorption by the starch granules due to the proteolytic and amylolytic activities of the dominant lactic acid bacteria in the sourdoughs) which made the dough less elastic. This in-turn improves the ability of the dough to trap and withstand the pressure of the expanding carbon dioxide in the fermenting dough and bread.
Thesis (PhD)--University of Pretoria, 2015.
gm2015
Food Science
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