Dissertations / Theses on the topic 'Dried milk. Milk'

The fortification of skim milk powder with vitamin A has been found to be ineffective with available methods. The purpose of this study was to assess new methods and materials for their effectiveness in providing stability to vitamin A in fortified skim milk powder. The first phase of the project involved trials in Pilot Plants which evaluated 14 different treatments for vitamin A stability during storage periods of twelve months at 22°C and six months at 37°C. The second and third phases of the experiment consisted of primary and instant powder trials in commercial plants using the most stable methods from the Pilot Plant trials. In the latter phases of the project, eight treatments were tested for primary powder and ten for instant type of powder. Results show that levels of antioxidants were important to control the oxidative degradation of vitamin A in the milk powder. The vitamin A concentrate containing BHA (5 mg), BHT (55 mg) and ⍺-tocopherol (12.5 mg) antioxidants produced the best results for primary powder. Ascorbyl palmitate-⍺-tocopherol combination of antioxidants was found to be more effective than the BHA-BHT-⍺-tocopherol blend for instant powder. The level of hydrogenated coconut oil (HCO) used as the vitamin carrier was also found to be important for stability, 0.2% being slightly better than 0.1% in primary powder. A 12% emulsion injected at such a rate as to add 0.027% oil in milk solids was the best treatment of the instant powder trials. Hay-like flavour in reconstituted skim milk powder was correlated with vitamin A destruction.
Land and Food Systems, Faculty of
Graduate

Preliminary experiments indicated that an acid casein co-precipitate could be produced by extrusion from skim milk powder (SMP). In assessing the problems encountered, experiments were designed to model and optimize the coagulation/washing process using response surface methodology (RSM), to minimize residual whey components and losses of fines. This study yielded useful information relative to improving our understanding of the coagulation mechanism and the most important variables affecting the process. In addition, RSM allowed multiresponse optimization of acid casein production using unique and newly developed optimization techniques. In order to simplify the process, an extruder die was designed to assist with the dewheying process, however, plugging problems occurred due to screw design limitations. Studies were implemented to determine the rheological behaviour of sodium caseinate and to evaluate the extruder performance in terms of energy consumption, and in terms of mixing and conveying through mathematical description of residence time distributions in the extruder. The knowledge gained from these studies was integrated to produce acid casein and sodium caseinate at pilot plant level and to conceive a plant layout of the process for the dairy industry. The process developed has many advantages, including the ability to produce a high quality product.

Master of Engineering
Spray dryers are the core components of a milk powder production plant, where the basic configuration usually features co-current flow of milk powder and air. Spray dryers have to be cleaned frequently due to powder deposit build-up on the walls. Powder deposit build-up gives rise to lower product yields and poses a potential fire risk. If the powder deposits are scorched (from being overheated) they will contaminate, and thus compromise, the quality and consumer safety of the final product, if the powder deposits fall in and mix with it. With milk powder production rates of most industrial spray dryers ranging from 4-28 tonnes of dry powder an hour, these wall deposition problems are significant. This problem is worth investigating because the outcome of reducing or eliminating wall deposition is that a spray dryer could operate for a longer period of time without having to be cleaned. Reduction in downtime due to cleaning would give rise to increased production time and possibly a reduction in the cost of manufacturing the product. The spray dryer used in this work was a modified short-form co-current Niro unit, fabricated from stainless steel. The spray dryer had an internal diameter of 0.80 m, narrowing down to 0.06 m at the base, and a height of 2 m. A two-fluid nozzle was used to spray the process fluids (water, skim milk and grape skin extract) into the drying chamber. To measure the wall deposition fluxes on the internal walls of the spray dryer, four stainless steel plates (dimensions 110 mm by 120 mm) were inserted in place of the windows that were previously used as sight glasses. A fifth plate (dimensions 110 mm by 120 mm) and a sixth plate (dimensions 110 mm by 110 mm) were also placed on the conical section of the spray dryer at different circumferential locations. Before this work, no quantitative data on the effects of spray dryer operating conditions on the wall deposition fluxes of food material were available. This work investigated the effect on the spray deposition flux of skim milk powder on the walls of the spray dryer of (i) flow patterns in the spray dryer, by changing the degree of swirl imparted to the incoming air by using three swirl vane angles of 0o, 25o and 30o, and (ii) the stickiness of the product, through first changing the temperature of the incoming air by using three inlet air temperatures of 170oC, 200oC and 230oC; and then changing the process fluid flowrate by using three flowrates of 1.4 kg hr-1, 1.6 kg hr-1 and 1.8 kg hr-1. Previous researchers have found that the extent to which water droplets spread out in the drying chamber is affected by the amount of swirl in the inlet air. This is likely to affect wall deposition fluxes because the particles will be closer to the walls if the droplets spread out widely. The results of this work have quantitatively confirmed that the spray deposition flux increases at higher swirl vane angles, where the spray deposition flux increased from 7 g m-2 hr-1 (swirl vane angle 0o) to 12.9 g m-2 hr-1 (swirl vane angle 30o). When a swirl vane angle of 0o was used, it was observed that the cross-sectional area of the spray cloud did not change very significantly with time. However, when a swirl vane angle of 25o was used, the spray cloud was observed to “flutter”, and when the swirl vane angle was increased to 30o, the spray cloud was observed to recirculate rapidly back in the direction of the nozzle. Thus, the chance of the particles being thrown further towards the walls of the chamber is likely to increase at higher swirl vane angles. This result suggests that higher wall deposition arises because more swirl is imparted to the air entering the dryer, which in turn affects the stability of the spray cloud and, therefore, the stability of the flow patterns in the spray dryer. The stickiness of the skim milk powder is related to the temperature and moisture content of the particles. In the past, the sticky-point curve has been suggested as a semi-quantitative concept in selecting operating conditions for spray drying food material containing carbohydrates, where it has been implied that there is no significant wall deposition below the sticky-point curve. This work has quantified the spray deposition in spray dryers with respect to the sticky-point curve, where the highest spray deposition flux of skim milk powder on the walls was 16 g m-2 hr-1, and the operating point corresponding to this spray deposition flux was located at and above the sticky-point curve. Hence, both particle stickiness and flow patterns affect the wall deposition of particles in a spray dryer. This work also investigated the effect of wall properties, namely a non-stick food grade material (nylon), adhesive tape and stainless steel, on the spray deposition flux of skim milk powder on the walls. The effect of electrostatics on wall deposition was studied by grounding the spray dryer and an anti-static agent was added to the skim milk to investigate if altering the properties of the feed material could reduce wall deposition. This work has quantitatively confirmed that cohesion occurs at the same rate as adhesion for skim milk powder in this spray dryer, because firstly, decreasing the adhesion tendency of the v wall by using nylon coating had no significant effect on the spray deposition flux compared with a smooth stainless steel wall and a wall covered with a double-sided adhesive tape; and secondly the powder collected on the walls was a linear function of time with and without adhesive on the plates. Furthermore, using a nylon coated wall did not eliminate wall deposition, and the wall deposition flux was found to be the same as when a stainless steel wall was used. This result further supports the finding here that spray deposition on the walls for skim milk powder is controlled by cohesion rather than adhesion. The spray dryer operating parameters that gave rise to the least spray deposition flux on the walls were a swirl vane angle of 0o, an inlet air temperature of 230oC and a process fluid flowrate of 1.4 kg hr-1. Decreasing the feed flowrate from 1.8 kg hr-1 to 1.4 kg hr-1 (decrease by 24%), with the inlet air temperature and swirl vane angle held constant, decreased the wall deposition flux by 43% from 7 g m-2 hr-1 to 4 g m-2 hr-1. Since the spray deposition flux on the walls decreased by 43% when the feed flowrate was decreased by 24%, it might be considered that the production process is in favour of a decrease in the feed flowrate to 1.4 kg hr-1 in this dryer, and consequently a decrease in the spray deposition flux on the walls per unit production output. Finally, this work investigated if the outlet moisture content from this small spray dryer used here was equilibrium limited or controlled by drying kinetics. The findings in this work confirmed the product moisture locus concept, which implies that the outlet moisture content of the skim milk particles approaches the equilibrium moisture content (in equilibrium with the outlet gas), and that the outlet moisture content of spray-dried food material containing carbohydrates is probably not limited by particle drying kinetics, even though the spray dryer is smaller (diameter 0.8 m, height 2 m) than those used in the dairy industry, typically with a diameter of 30 m and a height of 10 m.

Thesis (MSc Food Sc)--Stellenbosch University, 2004.
ENGLISH ABSTRACT: Kefir is a fermented dairy beverage resulting from the fermentation of milk with reusable Kefir grains. The grains consist of a complex combination of lactic acid bacteria and yeasts in a symbiotic relationship, embedded in a polysaccharide matrix called kefiran. Various problems are experienced during the commercialisation of the ready-made Kefir beverage and, therefore, it is more advantageous to market the grains, enabling the consumer to produce the beverage at home. Kefir grains could be mass-cultured and then preserved by Iyohilisation for successful long-term storage and easy distribution, during commercialisation. The microbial balance of the Kefir grains changes during both mass-culturing and freeze-drying, which will have an influence on the sensory properties of the Kefir beverage produced. The aim of this study was the optimisation of the production of Kefir from mass-cultured grains and from freezedried mass-cultured grains respectively. The sensory characteristics of the fermented beverages produced from these mass-cultured and preserved grains were determined. Mass-cultured Kefir grains were activated and Kefir produced using nine methods with different activation times and temperatures, different grain:milk ratios (36, 72 and 108 g grains.l⁻¹) and with different heat-treated milks (pasteurised, double pasteerised and UHT). The best Kefir beverage was produced by activation of the grains at 22°C for two successive 24 h incubation periods, followed by Kefir production at 22°C for 18 h and a maturation period at 18°C for 6 h. The milk was replaced before every incubation period, excluding the maturation period, and the fermentation vessel was swirled five times at the start of fermentation and after 18 h. This method resulted in a sour beverage with a thick consistency and the characteristic effervescence and flavour of Kefir. The optimal grain:milk ratio was identified as 36 g grains.l⁻¹ and the best heat-treated milks for the production of Kefir beverage were UHT and double pasteurised milk. Mass-cultured Kefir grains were freeze-dried for 1, 2, 3 and 6 d and the moisture loss determined. Freeze-dried grains were rehydrated for 1, 2, 6, 12 and 18 h to determine the optimal rehydration time. A sensory analysis was performed to compare the properties of Kefir produced from mass-cultured grains (Me), freeze-dried mass-cultured grains that were rehydrated and activated (FDRA) and activated mass-cultured grains that were freeze-dried and rehydrated (AFDR). The chemical compositions of mass-cultured grains (MC), mass-cultured, freezedried grains (MCFD), mass-cultured, freeze-dried grains that were rehydrated and activated (FDRA) and activated mass-cultured grains that were freeze-dried and rehydrated (AFDR), were also investigated. The optimum time to freeze-dry grains was 2 d and to rehydrate freeze-dried gtains was 1 h. The sensory analysis indicated that Kefir beverages prepared from FDRA and AFDR grains did not differ significantly and were less fermented than Kefir produced from MC grains. It was concluded that Kefir with excellent sensory characteristics can be produced from mass-cultured grains. Freeze-drying is a better method to preserve Kefir grains than freezing due to mass loss during freezing and easier distribution and storage of freeze-dried grains. The supplementation of freeze-dried grains with additional lactic acid bacteria and yeast isolates should be investigated.
AFRIKAANSE OPSOMMING: Kefir is 'n gefermenteerde suiwelproduk wat geproduseer word deur die fermentasie van melk met herbruikbare Kefirkorrels. Die korrels bestaan uit 'n komplekse kombinasie van melksuurbakterië en giste en is ingebed in 'n polisakkaried matriks genaamd kefiran. Verskeie probleme word ondervind met die kommersialisering van die klaar voorbereide Kefirdrankie en dit is meer voordelig om die korrels te bemark. Dit sal die verbruiker daartoe in staat stel om self Kefir tuis te produseer. Kefirkorrels kan in massa gekweek word en dan gevriesdroog word om langtermyn storing en verspreiding te vergemaklik tydens kommersialisering. Die spesifieke mikrobiese balans van die Kefirkorrels word tydens massakweking en vriesdroging versteur. Dus sal hierdie twee prosesse 'n invloed hê op die sensoriese eienskappe van die Kefir drankie geproduseer. Die doel van hierdie studie was die optimisering van die produksie van Kefir vanaf massagekweekte korrels en gevriesdroogde massagekweekte korrels. Die sensoriese karakteristieke van die Kefir geproduseer met hierdie korrels is ondersoek. Massagekweekte Kefirkorrels is geaktifeer en Kefir is geproduseer met nege verskillende metodes met variasies in die tyd en temperatuur kombinasies, verskillende korrel:melk verhoudings (36, 72 en 108g korrels.l⁻¹) en verskillende hittebehandelde melke (gepasteuriseerd, dubbel gepasteuriseer en UHT). Die beste Kefirdrankie is geproduseer deur die aktivering van die korrels by 22°C vir twee 24 h inkubasieperiodes, gevolg deur Kefir produksie by 22°C vir 18 uur en 'n verouderingsperiode by 18°C vir 6 h. Die melk was voor elke inkubasieperiode vervang, uitsluitende die verouderingsperiode. Die fermentasie houer is vyf maal gedraai aan die begin van fermentasie en na 12 h. Hierdie metode het gelei tot 'n drankie wat suur was met 'n dik konsistensie en die karakteristieke vonkeling en geur van Kefir. Die optimale korrel:melk ratio is geidentifiseer as 36 9 korrels.l⁻¹ en die verkieslike hittebehandelde melke is dubbel gepasteuriseerde en UHT melk. Massagekweekte Kefirkorrels was vir 1, 2, 3 en 6 dae gévriesdroog en die massaverlies is bepaal. Gevriesdroog korrels is gerehidreer vir 1, 2, 6, 12 en 18 h om die optimale rehidrasietyd te bepaal. 'n Sensoriese analise is uitgevoer om die eienskappe te vergelyk van Kefir geproduseer van massagekweekte korrels (MC), gevriesdroogde massagekweekte korrels wat gerehidreer en geaktiveer is (FDRA) en geaktiveerde massagekweekte korrels wat gevriesdroog en gerehidreed is (AFDR). Die chemiese samestelling van massagekweekte korrels (MC), massagekweekte, gevriesdroogde korrels (MCFD), massagekweekte, gevriesdroogde korrels wat gerehidreer en geaktiveer is (FDRA) en geaktiveerde massagekweekte korrels wat gevriesdroog en gerehidreer is (AFDR), is bepaal. Die optimum tydperk vir vriesdroging van korrels was 2 d en vir rehidrasie van gevriesdroogde korrels was 1 h. Die sensoriese analise het aangedui dat Kefir wat van FDRA en AFDR korrels geproduseer is, nie betekenisvol van mekaar verskil het nie, maar minder gefennenteerd was as Kefir wat van Me korrels geproduseer is. Die gevolgtrekking is gemaak dat 'n Kefirdrankie met uitstekende eienskappe geproduseer kan word met massagekweekte korrels. Vriesdroging is 'n beter metode as bevriesing om Kefirkorrels te preserveer a.g.v die ver1iesvan massa tydens bevriesing en die vergemakliking van vervoer en verspreiding van gevriesdroogde korrels. Die aanvulling van gevriesdroogde korrels met addisionele melksuurbakterieêen giste moet nog ondersoek word.

Class of 2017 Abstract
Objectives: Milk protein allergy is estimated to affect 1.2% to as much as 17% of people of all ages. Advair® Diskus® (FP/SX) utilizes lactose as an excipient which limits the utility of this product for this population. Furthermore, Advair® Diskus® is formulated as an interactive physical mixture via a micronization process. Alternatively, spray dried engineering achieves narrow particle size distribution, allowing greater deposition in the targeted respiratory bronchioles. The purpose of this dry powder inhaler (DPI) study was to conduct an in vitro comparative analysis of the aerodynamic performance of a co-spray dried lactose-free formulation of FP/SX with a mannitol excipient as a molecular mixture versus the Advair® Diskus® 250/50 (FP/SX) interactive physical mixture product. Methods: Utilizing mannitol as an excipient, a co-spray dried FP/SX powder was prepared using the Buchi Mini-Spray Dryer B-290 under closed system configuration. The resulting feed solution was spray dried at pump rates of 25%, 50%, and 100% with all other parameters remaining constant (aspiration, atomization rate, nitrogen gas rate). The primary outcome measure, aerodynamic performance, was assessed using the Copley Next-Generation Impactor (NGI). NGI data for the DPIs was used to calculate mass median aerodynamic diameter (MMAD), geometric standard deviation (GSD), and fine particle fraction (FPF) of each powder, including the Advair® Diskus®. Residual water content was quantified by Karl Fischer titration. Particle characteristics were visualized by scanning electron microscopy. Results: FPF, MMAD, and GSD were calculated from NGI data; Wolfram Alpha software was used to calculate MMAD and GSD. T-test regression was used for comparative analysis of spray-dried and Advair® Diskus® powders. MMAD for each spray dried sample was analyzed using a t-test regression against the MMAD values from the Advair® Diskus®. Using aerodynamic analysis studies triplicated for each powder, there was no significant difference between the spray dried powder and Advair® Diskus® for MMAD and GSD (p-values >0.05). The 50% and 100% pump rate samples had similar FPF to the Advair® Diskus® (p-values >0.05). However, the 25% pump rate sample had a significantly improved FPF compared to the Advair® Diskus® (p <0.01). Conclusions: A co-spray-dried lactose-free formulation of FP/SX with a mannitol excipient demonstrated similar aerodynamic performance to the Advair® Diskus® which consists of a physical mixture of two drugs with lactose. Of significance, 25% pump rate spray-dry conditions demonstrated an improved FPF compared to the Advair® Diskus®.

Spores of thermophilic bacilli are a common concern during the manufacture of milk powder. Spores are believed to occur in high numbers in milk powder due to their ability to survive pasteurisation, attach to stainless steel surfaces, germinate, grow as biofilms and subsequently enter the product stream and thereby contaminate the final product. In this study, thirty one thermophilic bacilli isolates were obtained from a New Zealand milk powder production line and identified as either Anoxybacillus flavithermus or Geobacillus spp. using random amplified polymorphic DNA (RAPD) and species-specific PCR. Sporulation media and a polyethylene glycol two-phase separation system were modified to produce high yields of spores free from debris. The spores of four Geobacillus spp. isolates (CGT-8, D4, E7 and E11) were characterised in terms of structure (electron microscopy), surface charge (zeta potential), hydrophobicity (contact angle and microbial adhesion to hexadecane) and attenuated total reflectance infrared spectroscopy (ATR-IR). Spores from three of the four isolates possessed an exosporium while the fourth did not. However the integrity of the exosporium varied over time. The spores were negatively charged (-10 to -20 mV) at neutral pH and high ionic strength (0.1 M KC1). Both hydrophobicity assays revealed that the spores of the four isolates were relatively hydrophilic while ATR-IR revealed the spores' surfaces consisted of protein and polysaccharides. The influence of these spore characteristics on adhesion to a variety of substrata under high flow rates was examined using the extended Derjaguin, Landau, Verwey and Overbeek (XDLVO) theory. Spores generally attached in higher numbers to hydrophobic surfaces compared to hydrophilic surfaces, however this observation was more prevalent for isolate D4. This result indicated that a single mechanism could not describe the adhesion of spores from different strains. A series of glass surfaces with modified characteristics were produced in order to test the antifouling properties on the adhesion of D4 spores. Spores suspended in a high ionic strength medium (0.1 M KC1) attached in greater numbers (1 Log₁₀ CFU cm⁻�) to positively charged and hydrophobic surfaces compared with negatively charged and hydrophilic surfaces. A clean in place (CIP) procedure, reduced spore numbers on hydrophobic and hydrophilic surfaces by 1.5 and by 2.0 Log₁₀ CFU cm⁻�, respectively. When spores were suspended in milk, there was little difference in the number of spores attaching to the different surfaces (ie. 3.5 to 3.8 Log₁₀ CFU cm⁻�), and spore removal from surfaces via a CIP regime was unchanged (1.5 to 2.0 Log₁₀ CFU cm⁻� reduction) compared with spores that attached in simple 1:1 electrolyte media. The effects of a caustic wash on spore surface characteristics and adhesion was determined. There was a significant reduction in spore viability (2 Log₁₀ CFU mL⁻�) after a 30 min caustic wash at 65 �C in the current study, however surviving spores displayed a greater propensity to attach to stainless steel. Surface characterisation results revealed an increase in hydrophobicity and a greater negative charge on the spores' surface after treatment with NaOH. Surviving spores could potentially recontaminate sections of the plant which are cleaned with this recycled caustic wash solution, thereby seeding surfaces with spores at the beginning of the next processing run. In conclusion, while surfaces that reduce spore adhesion and enhance removal can be produced, exposure to complex solutions such as milk can reduce the anti-fouling effectiveness of such surfaces to spore adhesion.

Ce travail vise a mettre en relation les caracteristiques physico-chimiques des laits reconstitues et leur aptitude fromagere et a determiner l'influence des conditions de fabrication des poudres sur ces aptitudes. Dans une premiere etape, l'etude a porte sur le comportement de sept lots de laits reconstitues au cours de la coagulation par la presure et en microfabrications fromageres de type pate molle et pate pressee. Dans une seconde etape, l'etude concernant sept nouveaux lots, a comporte la determination des caracteres physico-chimiques, rheologiques et fromagers de ces poudres. Les resultats montrent des differences significatives entre les types de poudres aux plans des comportements rheologiques et fromager mais il n'est pas observe de correlation entre caracteres physico-chimiques et technologiques sauf pour ce qui concerne l'indice de traitement thermique qui est etroitement correle avec tous les caracteres technologiques. Des analyses en composantes principales (a. C. P. ) et une analyse de variance

L'aéroacoustique est une filière de l'acoustique qui étudie la génération de bruit par un mouvement fluidique turbulent ou par les forces aérodynamiques qui interagissent avec les surfaces. Ce secteur en pleine croissance a attiré des intérêts récents en raison de l'évolution de la transportation aérienne, terrestre et spatiale. Les microphones avec une bande passante de plusieurs centaines de kHz et une plage dynamique couvrant de 40Pa à 4 kPa sont nécessaires pour les mesures aéroacoustiques. Dans cette thèse, deux microphones MEMS de type piézorésistif à base de silicium polycristallin (poly-Si) latéralement cristallisé par l'induction métallique (MILC) sont conçus et fabriqués en utilisant respectivement les techniques de microfabrication de surface et de volume. Ces microphones sont calibrés à l'aide d'une source d'onde de choc (N-wave) générée par une étincelle électrique. Pour l'échantillon fabriqué par le micro-usinage de surface, la sensibilité statique mesurée est 0.4μV/V/Pa, la sensibilité dynamique est 0.033μV/V/Pa et la plage fréquentielle couvre à partir de 100 kHz avec une fréquence du premier mode de résonance à 400kHz. Pour l'échantillon fabriqué par le micro-usinage de volume, la sensibilité statique mesurée est 0.28μV/V/Pa, la sensibilité dynamique est 0.33μV/V/Pa et la plage fréquentielle couvre à partir de 6 kHz avec une fréquence du premier mode de résonance à 715kHz.

L'aéroacoustique est une filière de l'acoustique qui étudie la génération de bruit par un mouvement fluidique turbulent ou par les forces aérodynamiques qui interagissent avec les surfaces. Ce secteur en pleine croissance a attiré des intérêts récents en raison de l'évolution de la transportation aérienne, terrestre et spatiale. Alors que les tests sur un objet réel sont possibles, leur implantation est généralement compliquée et les résultats sont facilement corrompus par le bruit ambiant. Par conséquent, les tests plus strictement contrôlés au laboratoire utilisant les modèles de dimensions réduites sont préférables. Toutefois, lorsque les dimensions sont réduites par un facteur de M, l'amplitude et la bande passante des ondes acoustiques correspondantes se multiplient respectivement par 10logM en décibels et par M. Les microphones avec une bande passante de plusieurs centaines de kHz et une plage dynamique couvrant de 40Pa à 4 kPa sont ainsi nécessaires pour les mesures aéroacoustiques. Les microphones MEMS ont été étudiés depuis plus de vingt ans, et plus récemment, l'industrie des semiconducteurs se concentre de plus en plus sur ce domaine. Par rapport à tous les autres principes de fonctionnement, grâce à la miniaturisation, les microphones de type piézorésistif peuvent atteindre une bande passante plus élevée et ils sont ainsi bien adaptés pour les mesures aéroacoustiques. Dans cette thèse, deux microphones MEMS de type piézorésistif à base de silicium polycristallin (poly-Si) latéralement cristallisé par l'induction métallique (MILC) sont conçus et fabriqués en utilisant respectivement les techniques de microfabrication de surface et de volume. Ces microphones sont calibrés à l'aide d'une source d'onde de choc (N-wave) générée par une étincelle électrique. Pour l'échantillon fabriqué par le micro-usinage de surface, la sensibilité statique mesurée est de 0.4 μV/V/Pa, la sensibilité dynamique est de 0.033 μV/V/Pa et la plage fréquentielle commence à 100 kHz avec une fréquence du premier mode de résonance à 400 kHz. Pour l'échantillon fabriqué par le micro-usinage de volume, la sensibilité statique mesurée est de 0.28 μV/V/Pa, la sensibilité dynamique est de 0.33 μV/V/Pa et la plage fréquentielle commence à 6 kHz avec une fréquence du premier mode de résonance à 715 kHz.

2008年三鹿三聚氰胺毒奶粉事件震驚國內外，該事件導致六名嬰兒腎結石死亡，逾三萬嬰幼兒從此生活在各種腎疾病的陰霾之下。此後奶產品安全問題尋出不窮，對國內奶產業造成嚴重的負面影響，令消費者對整個國內奶產業信心下降。事實上，在很多奶產品安全的危機中，遭受質疑的企業組織最後均被政府的檢測結果證實是無辜的。在危機中，組織的形象受到威脅，組織需通過不同的方法進行自我辯護。現存的文獻提出，危機溝通策略和組織對責任承擔的態度是兩個影響公眾對組織信心和媒體報導語調的重要因素。組織類型（國有或外資）也會影響公眾對組織的信心和媒體報導語調。過往研究也發現，公眾對組織的信心與媒體報導語調之間存在正相關的聯繫。此研究通過對兩個犯行危機情景的案例研究（2009多美滋危機事件和2010聖元危機事件），目的在於評估危機溝通策略的效用，同時也探討在不同的階段中危機溝通策略、組織責任承擔、組織類型、公眾對組織的信心和媒體報導語調之間的關係。研究成果發現文獻建議之在不同階段的最佳策略和組織責任承擔對公眾對組織的信心和媒體報導語調均無重要影響。然而，使用越少藉口和越多提供信息策略的組織贏得更多公眾信心，從而提升正面媒體報導。研究也發現，外企在第一和第二階段報導更正面，但最後國企反而取得正面的媒體報導。另外，組織類型與階段對組織選取策略與組織責任承擔均有影響。本研究結果顯示西方危機處理理論在低信任度社會如中國等未必適用。研究一方面透過更複雜的情境角度，進一步加深對現有危機傳播文獻的理解，例如引入不同階段的概念來評估危機管理的成效，另一方面也為在低信任社會中的奶產業企業提供有效的危機管理建議。
Sanlu Melamine-contaminated Milk Scandal, the frequent outbreak of dairy product safety crises had a severe impact on the domestic dairy industry, resulting in a general loss of the consumers' confidence in the entire domestic dairy industry. In fact, in many crises the crisis-ridden organizations were eventually proven innocent by governmental departments. During a crisis, an organization's image is threatened, so that various communicative entities are used to defend this image. Based on the existing literature, this study aims at evaluating the effectiveness of crisis communicative strategies (CCSs) as well as investigating the relationships among CCSs, organization responsibility acceptance, organization ownership type (domestically owned or foreign-invested), confidence in organization and media coverage in different stages during the crisis by comparing the Dumex case in 2009 and the Synutra case in 2010. The results found that the posited optimal CCS in a particular stage and organization responsibility acceptance generally did not have significant effects on confidence in organization or media image coverage. However, the findings revealed that the less excuses and the more information providing strategies were employed, the higher the stakeholders' confidence in organization would be, which in turn significantly increased the positive image coverage. Certain CCSs, i.e., diversion, no response, also showed significant direct effects on media coverage. Moreover, foreign-invested organization appeared to enjoy favorable image coverage in Stage 1 and Stage 2, but domestically owned organization surpassed it in the last stage. Organization ownership type and stages also had significant impacts on the choices of CCSs and degree of organization responsibility acceptance. Stage was also a significant negative predictor of confidence in organization but not for media coverage. This study on one hand revealed that the western crisis management theory might not be accommodative to the low-trust context in mainland China and thus theoretically further the understanding of existing crisis communication literature in a more complex contextual perspective through integrating stages as a significant time factor into the evaluation of crisis management. On the other hand it also pragmatically provides useful suggestions on effective crisis strategic management to dairy corporate in low-trust societies.
Detailed summary in vernacular field only.
Huang, Peiyi.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2012.
Includes bibliographical references (leaves 159-177).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstracts also in Chinese; appendixes in Chinese.
ABSTRACT (English version) --- p.i
ABSTRACT (Chinese version) --- p.iii
ACKNOWLEDGEMENT --- p.v
TABLE OF CONTENTS --- p.ix
Chapter 1. --- INTRODUCTION --- p.1
Chapter 2. --- CONCEPTUALIZATION --- p.9
Chapter 2.1 --- Crisis Management --- p.9
Crisis --- p.9
Crisis Management --- p.11
Chapter 2.2 --- Outcome: Media Image Coverage --- p.14
Chapter 2.3 --- Time Factor: Stages --- p.16
Chapter 2.4 --- Strategic Factors --- p.20
Crisis Communicative Strategies (CCSs) --- p.20
Organization Responsibility Acceptance --- p.46
Chapter 2.5 --- Organizational Factor: Organization Ownership Type --- p.50
Chapter 2.6 --- Mediator: Confidence in Organization --- p.52
Chapter 2.7 --- Research Framework, Hypotheses and Research Questions --- p.55
Chapter 3. --- METHODOLOGY --- p.58
Chapter 3.1 --- Case Selection --- p.58
Case --- p.58
Design --- p.61
Chapter 3.2 --- Content Analysis --- p.65
Data Collection --- p.65
Data Coding --- p.67
Inter-coder Reliability --- p.70
Chapter 4. --- RESULTS --- p.71
Chapter 4.1 --- Basic Sample Information --- p.71
Chapter 4.2 --- Hypothesis Tests of Two Individual Cases --- p.71
Case 1 (Dumex) --- p.73
Chapter tCase 2 (Synutra) --- p.86
Chapter 4.3 --- The Overall Results of Cases and Research Questions --- p.91
Media Valance --- p.92
Research Question 1 --- p.95
Research Question 2 --- p.99
Research Question 3 --- p.107
Chapter 4.4 --- Summary of the Findings --- p.116
Chapter 5. --- DISCUSSIONS AND IMPLICATIONS --- p.126
Chapter 5.1 --- Stage as A Complex Concept --- p.126
Controlling Other Dangers in a Dynamics Crisis --- p.127
The Role of Governmental Intervention in a Low-trust Society --- p.129
Chapter 5.2 --- Effects of CCSs on Media Image Coverage inLow-trust Society --- p.132
Chapter 5.3 --- Mediating Effects of Confidence in Organization --- p.139
Chapter 5.4 --- Suggestions of Applications of CCSs in Low-trust Society --- p.141
Chapter 5.5 --- Limit Predictive Power of Organization Responsibility Acceptance --- p.148
Chapter 5.6 --- Effects of Organization Ownership Type --- p.150
Chapter 6. --- LIMITATIONS AND FUTURE RESEARCH DIRECTIONS --- p.154
Chapter 7. --- REFERENCES --- p.159
Chapter 8. --- APPENDIXES --- p.178

Submitted in fulfilment of the requirements for the Degree of Master of Technology: Marketing, Durban University of Technology, 2008.
The purpose of this study was to evaluate Chinese parents' buying behaviour towards baby milk powder in the context of China's One-Child policy. The study examined the Chinese culture, social trends, the influence of product attributes among urban Chinese parents and parents' product knowledge of baby milk powder. This study is an exploratory study. A questionnaire was used to collect the data from 400 respondents at Shangdong University, China. There are 312 respondents' questionnaires used to analyse the results. The results were discovered through the use of four research objectives. Firstly, the results reflect that family and friends do have an influence on buying decisions on baby milk powder. There parents rely more on word-of-mouth communication and shop assistants play a negative role in parents' buying decision. Secondly, mothers need to opt for baby milk powder for their babies due to the flood of women into the job market and incomes from dual earners. Thirdly, parents perceive high price with good quality; the preferred brand by the parents have a significant impact on their brand loyalty and parents generally hold positive views of foreign-made baby milk powder. Fourthly, parents have a high level of subjective and objective knowledge of baby milk powder. This study was limited to the sample size and the geographic area. Consequently, results of this study can not be regarded as representative of the entire Chinese population. The results may help marketers develop more effective marketing programmes to affect consumers' buying decision. In addition, this study is one of a few studies that apply the theory of buying behaviour in the context of China's One-Child policy in the marketing field.
M

Agglomerated milk powders are produced to give improved properties such as flowability, dispersibility, reduced dustiness and decreased bulk density. A key function of these powders is to dissolve "instantly" upon addition to water and because of this they are also called "instant milk powders". They are produced by agglomerating the undersized fines that are returned to the top of the spray drier with milk concentrate droplet spray. Interaction occurs in a collision zone, often with multiple sprays and fines return lines. Agglomeration can be a difficult process to control and operators find it hard to fine tune the process to produce specific powder properties. This work aimed to understand the effects of key droplet and fines properties on the extent of agglomeration to allow a mechanistic understanding of the process. Three scales of spray drier were investigated in this study with different rates of evaporation; a small scale drier (0.5 - 7 kg water h-1), a pilot scale drier (80 kg water h-1) and a range of commercial production scale driers (4 - 15 000 kg water h-1). A survey of operators of commercial scale driers showed that control of instant milk powder production to influence bulk density is highly intuitive. Fines recycle rates were expected to be important in control of agglomeration processes and were estimated on a specific plant by using the pressure drop measured in the fines return line. A model based on pressure drop along a pneumatic pipeline under-predicted the experimental values for pressure drop due to solids, which means a calibration curve should be generated for each specific drier. Fines recycle rates were predicted to be significantly higher at 95 to 130 % of production rates compared to those expected by operators of 50%. Experimental measurements agreed with existing models for the effect of temperature on the density and viscosity of milk concentrates. Experimental results showed that the surface tensions of concentrated milks were within the same range as literature values for standard milks below 60°C, but were significantly higher for milk above 60°C. This is thought to be linked to the mechanism of skin formation due to disulphide cross linking at high temperatures and concentrations. Powder properties were also established for selected products produced on the commercial scale driers. These powders were then used in experiments on the two smaller driers. Because collision frequency depends on the velocity and droplet size of sprays; these properties were measured for the small scale drier and estimated, where possible, for the pilot and commercial driers. The small scale agglomerating spray drier was configured to alter droplet and particle properties when interacting a vertical fines particle curtain with a horizontal spray sheet. An extensive design and improvement process was carried out to ensure the system consistently delivered these streams in a controllable manner. The processes of collision and adhesion occur very quickly inside the spray drier. In order to assess the extent of agglomeration that has occurred, the feed streams must be compared to the final product stream. An ideal way to do this is to use an agglomeration index which compares the particle size distributions of the feed (fines recycle and spray streams) and the particle size distribution of the product stream (the agglomerated powder). The index described changes between these steams across the particle size distribution and is called an agglomeration efficiency, ξg. However, it was found that the presence of fines in the product of the one-pass design obscured the agglomerates formed. The agglomeration efficiency, ξg, was modified to become ξh which subtracted the fines stream from the agglomerated product distribution. In this way ξh models industrial operation where the fines are recycled, by effectively just comparing the spray and product streams entering and leaving the process. The small scale drier was used for an experimental study on natural and forced agglomeration, where the drier was operated with spray only, then with spray and fines. For natural agglomeration, SEM images of the product powder indicated that little agglomeration occurred between spray droplets. The product yield was unacceptably low (~ 40%) due to adhesion of spray droplets to the drying chamber wall opposing the horizontal spray. When the fines curtain was introduced in the forced agglomeration experiments, product yield increased above 50% because the fines acted as collectors for the spray droplets. However, the agglomeration performance of the modified spray drier was lower than expected. The equipment design was then optimised by considering three key issues; fines dispersion, droplet dispersion and stickiness, and agglomerate breakdown. Final experiments studied agglomeration at low fines to spray mass flux ratios and showed that increasing the fines size had a positive effect on agglomeration efficiency,ξh. The agglomeration study at pilot scale identified the effect of key variables, total solids, concentrate and fines flow rate, and fines size on the agglomeration efficiency. A dimensionless flux approach was used to explain the experimental results. The fines to spray mass flux ratio and the projected area flux ratio (at constant concentrate flow rate) were found to be the most suitable to represent the physical processes during agglomeration. Experimental results showed that a higher dimensionless flux resulted in more agglomeration and as well as small fines size and atomising low solids concentrate. The critical Stokes number highlighted the importance of particle size and collision velocity on the outcome of the collision as well as the importance of stickiness on adherence following the collision. A statistical analysis established a relational model for predicting the agglomeration efficiency based on fines size, total solids and the fines to spray mass flux ratio. This thesis has gained insight into agglomeration processes during spray drying and knowledge about how to define the extent of agglomeration. Practical findings from this research can have a significant impact on successful spray drying operation for instant powders. There are some practical steps to be taken industrially to promote the control of agglomerating spray driers. The first step is to measure and control the flow of fines recycled to the top of the spray drier. The next step is to validate the findings at industrial scale and link the agglomeration index to the bulk powder properties. However, there are many challenges that remain to be tackled in the area of milk powder agglomeration. Milk powder agglomeration at the top of the spray drier is a complex process involving many different variables. A more detailed study of the micro processes that occur during agglomeration will give increased understanding of the relationships between key operating variables and agglomerate properties.

Encapsulation of lipids and other oxidizable compounds provides a means of protecting these compounds against their environment, including such factors as oxygen and humidity. The physical properties of wall matrices have a major influence on the oxidative stability of encapsulated lipids. This study investigated the effects of composition and processing conditions on physical and chemical stability of encapsulated milk fat powder (dairy creamer). Achieving a stable liquid emulsion is a necessary first step. Emulsifier type and concentration as well as processing conditions affected oil droplet size distribution. Larger oil droplet size led to an unstable emulsion and a consequential increase in surface fat of spray dried powder. At best, about 98% of the milk fat was encapsulated (average oil droplet size ∼0.5 μm, 2.0% lecithin, 36 DE corn syrup solids). The physical properties of spray dried powders that were studied include internal and external morphology, water sorption isotherm, surface fat, true density, and melting and crystallization. Upon storage, physical changes led to a complex change in surface fat with storage humidity, crystallization of carbohydrates (at higher %RH), and caking. These were dependent on maltodextrin dextrose equivalent (DE) and storage humidity. Oxidative stability of milk fat encapsulated in powder with DE-36 corn syrup solids was studied at 14–52%RH and 25°C (Collaborative work with two other investigators; Dr. Nitin Hardas and John L. Foley). Oxidation was negligible for powders stored in the dark at all relative humidities. Under UV light, the encapsulated fat significantly increased in peroxide value (PV) and decreased in 18:2 and 18:3 fatty acids over time. The highest rate of oxidation was found at 52% RH, indicating increased diffusivity of oxygen and other components under this condition. In contrast, surface fat oxidative rate was slower at 52% than at 14% and 44% RH. Overall oxidative stability was dominated by the encapsulated fraction although in general the surface fat fraction was oxidized more rapidly.

The objective of this study was to examine the effects of feeding extruded and non-extruded mixtures of wheat dried distillers grains with solubles with peas (WP) or canola meal (WC) on ruminal fermentation, total tract nutrient digestion and milk production in dairy cows. Eight dairy cows (712 ± 54 kg body weight; 90 ± 31 days-in-milk at the beginning of the experiment) were used in a replicated 4 × 4 Latin square design (28-d periods) with a 2 × 2 factorial arrangement of dietary treatments. Four cows in one Latin square were fitted with rumen cannulas for the measurement of ruminal fermentation characteristics. Treatment diets contained either WP or WC combinations fed in an extruded or non-extruded form (16% of DMI). Diets were isonitrogenous (17.1% crude protein; CP) and contained approximately 53% concentrate and 47% forage (DM basis). Dietary treatment had no significant effect on DMI (P > 0.10). Starch intake was higher for cows fed extruded diets compared to those fed non-extruded diets (P = 0.028) and was also higher for cows fed WP compared to those fed WC (P = 0.042). Cows fed extruded diets had higher apparent ruminal digestion of DM (P = 0.02) and a tendency (P = 0.05) for a higher OM apparently digested in the rumen compared to those fed non-extruded diets. Total tract digestibilities of organic matter (P < 0.01), CP (P < 0.01), ether extract (P < 0.01) and starch (P = 0.047) were higher for cows fed extruded diets compared to those fed non-extruded diets. Total tract digestibility of ether extract was lower (P = 0.011) but digestibility of starch was higher (P < 0.01) and CP digestibility tended to be higher (P = 0.08) for cows fed WP compared to those fed WC. Fecal N excretion was lower in cows fed extruded diets compared to those fed non-extruded diets (P < 0.01), but there was no difference in N retention, productive N, RDP or RUP between diets (P > 0.10). Ruminal pH was higher for cows fed non-extruded WC compared to those fed extruded WC, but there was no difference between WP diets (interaction; P = 0.047). Ruminal acetate displayed the opposite interaction where concentration was highest for cows fed extruded WC and lowest for those fed non-extruded WC but there was no difference between WP diets (interaction; P = 0.019). Ruminal ammonia-N concentration tended to be higher for cows fed WC compared to those fed WP (P = 0.06). Ruminal propionate concentration was higher for cows fed extruded diets compare to those fed non-extruded diets (P = 0.026). Ruminal isobutyrate concentration was higher for cows fed WC compared to those fed WP (P < 0.01). Ruminal butyrate (P < 0.01) and isovalerate (P < 0.01) concentrations were higher for cows fed extruded WC compared to those fed non-extruded WC, but concentrations decreased for cows fed extruded WP compared to those fed non-extruded WP. Plasma glucose concentration was higher for cows fed WC compared to those fed WP but concentration was highest for cows fed extruded WC but lowest for cows fed extruded WP (interaction; P < 0.01). Milk protein yield (P = 0.047) was higher and milk yield tended to be higher (P = 0.06) for cows fed WP compared to those fed WC diets. Milk protein content was not affected by diet; however, milk fat content (P = 0.04) and MUN (P = 0.011) were lower, whereas milk yield (P = 0.030), 3.5% fat corrected milk yield (P = 0.027), milk fat yield (P = 0.027), lactose content (P = 0.011) and lactose yield (P < 0.01) were higher in cows fed the extruded diets compared to those fed non-extruded diets. In summary, these results indicate that extrusion had positive effects on overall milk production and total tract nutrient digestion.

A series of experiments were conducted to determine nutritional strategies to improve the efficiency of N utilization in dairy cows when feeding co-products including wheat-based (W-DDGS) and corn-wheat blend distillers grains with solubles (B-DDGS), and dried whey permeate (DWP). In Experiment 1, the objective was to determine the effects of replacing canola meal (CM) as the major protein source with W-DDGS on ruminal fermentation, microbial protein production, omasal nutrient flow, and animal performance. Cows were fed either a standard barley silage-based total mixed ration containing CM as the major protein supplement (0% W-DDGS, control) or diets formulated to contain 10, 15 and 20% W-DDGS (dry matter [DM] basis), with W-DDGS replacing primarily CM. Diets were isonitrogenous (18.9% crude protein [CP]). Inclusion of W-DDGS to the diet did not negatively affect ruminal fermentation, microbial protein production, and omasal nutrient flow. However, there was a 0.7- to 2.4-kg increase in DM intake, and a 1.2- to 1.8-kg increase in milk yield after the addition of W-DDGS in place of CM. In Experiment 2, the objective was to delineate the effects of including either W-DDGS or B-DDGS dried distillers grains with solubles as the major protein source in low or high CP diets fed to dairy cows on ruminal function, microbial protein synthesis, omasal nutrient flows, urea-N recycling, and milk production. The treatment factors were type of distillers co-product (W-DDGS vs. B-DDGS) and dietary CP content (15.2 vs. 17.3%; DM basis). The B-DDGS was produced from a mixture of 15% wheat and 85% corn grain. All diets were formulated to contain 10% W-DDGS or B-DDGS on a DM basis. Feeding up to 10% of dietary DM as B-DDGS or W-DDGS as the major source of protein did not have negative effects on metabolizable protein (MP) supply and milk production in dairy cows. However, reducing dietary CP content from 17.3 to 15.2% decreased milk production. This response was attributed to an insufficient supply of ruminally degradable protein (RDP) that suppressed microbial nonammonia N (NAN) synthesis in the rumen, thus decreasing intestinal MP supply. In Experiment 3, the objective was to determine the effects of replacing barley or corn starch with lactose (as DWP) in diets containing 10% W-DDGS on ruminal function, omasal nutrient flow, and lactation performance. The treatment factors were source of starch (barley vs. corn) and dietary inclusion level of DWP (0 vs. 6%; DM basis) as a partial replacement for starch. Diets were isonitrogenous (18% CP) and contained 3 or 8% total sugar. The starch content of the low sugar diet was 24% compared to 20% for the high sugar diet. Dry matter intake, and milk and milk component yields did not differ with diet. However, partially replacing dietary corn or barley starch with sugar up-regulated ruminal acetate and propionate absorption, and reduced ruminal NH3-N concentration, but had no effect on ruminal pH, microbial protein synthesis, omasal nutrient flow and production in dairy cows. In summary, data presented in this thesis indicate that W-DDGS and B-DDGS can be included as the major source of protein in dairy cow diets without compromising ruminal function, nutrient supply and milk production in dairy cows. Feeding medium to low CP diets, and partial replacement of starch with sugar in diets containing W-DDGS and B-DDGS can improve N utilization efficiency in dairy cows. Additionally, an upregulation of facilitated transport of acetate and propionate across epithelial cells possibly prevents the occurrence of ruminal acidosis when lactose partially replaces starch in cow diets.