Thesis (M.Sc.) -- University of Western Sydney, Hawkesbury, 1997. / Includes bibliographical references (leaves 168-205).

No description available.

Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves.

published_or_final_version / Botany / Master / Master of Philosophy

Batters are highly complex systems with wide ranging ingredients including flours, water, flavorings, and spices. Interactions between the ingredients determine the performance of batters and the final quality of coated products. Addition of hydrocolloids into batters of different types of flour provides special effects on batter performance. The functionalities of hydrocolloids-flour mixtures in terms of the thermal and rheological properties of the resulting batter systems were investigated in this study. / The rheological properties of the batter were determined using a strain/stress control rheometer. A steady state method was used to measure the viscosity as a function of the shear rate varying from 0.5 to 150 s-1 at 15°C. The resulting data was then fitted to the Herschel-Bulkley Model. The viscoelastic properties were monitored as a function of temperature and were determined using a dynamic oscillatory test. Two different temperature profiles were used to simulate cooking and storage processes. Differential scanning calorimetry (DSC) was used to determine thermal properties (namely glass transition temperature, gelatinization temperature, ice melting temperature, and enthalpy) and to describe the phase transitions that occur during heating and cooling processes. / The rheological and thermal properties varied for different types of flours and their combination ratios, as well as different types of hydrocolloids at different concentrations. The replacement of corn flour greatly altered the viscosity and viscoelastic properties of wheat based and rice based batter systems. Using 100% corn flour based batter showed highest yield stress, whereas 100% rice flour based batter did not show any yield stress. Higher temperatures and longer times were required to gelatinize starch at the higher levels of rice flour for each batter system flour mix combination. The various combination ratios of the flours apparently did not significant influence the gelatinization temperatures of the batter systems. However they significantly influence the total enthalpies (DeltaHG) of the various samples. Wheat flour based batters showed the lowest glass transition temperatures. Thermal properties of wheat-based batters were influenced by the replacement of wheat with rice or corn flours. Corn flour based batters required considerably more energy for gelatinization during the cooking process. / Hydrocolloids lowered flow behavior index (n) and increased the consistency index (k) of all batters. The gums also changed the onset temperature of structure development and the storage and loss moduli of the batter systems. Hydrocolloids greatly influenced the thermal properties of batter systems. The gums shifted gelatinization temperature and depressed glass transition temperature of resulting batter systems. Further, MC increased the melting temperature (Tm) for the test batter systems as compared with the values for the control system without methylcellulose (MC). Carboxymethylcellulose (CMC) did not show statistically significant effects on the total enthalpies of ice melting for all samples. However, MC and CMC showed more pronounced effects on rice, corn, and their combined flour based batters than it did on wheat flour based batters. However, this characteristic does not show in batter systems containing xanthan gum.

No description available.

This thesis reports the use of capillary electrophoresis (CE) for the analysis of carrageenans, anionic polysaccharides extracted from red seaweeds and widely used in the food industry for their gelling and thickening properties. The three main types, kappa, iota and lambda, differ in the number of sulfate groups and the presence or absence of a 3,6-anhydro bridge in the disaccharide residue repeat unit. CE separates analytes according to their charge to frictional coefficient ratios, therefore it is suitable to separate these biopolymers. In order to detect polysaccharides in CE, our approach consisted in derivatising the reducing ends of the saccharides by reductive arnination with a fluorophore, l-arninopyrene-3,6,8- trisulfonate (APTS). This allowed sensitive detection by laser induced fluorescence. Method development gave optimal conditions for separation using a polyvinyl alcohol coated capillary and a 25 mM ammonium acetate, pH 8.0 background electrolyte. The effects of changes of both instrumental parameters (temperature, injection mode, field strength) and, the composition of the BGE (concentration and pH) are reported, and explained in terms of the physical chemistry of the BGE and the biopolymers. The conditions of the derivatisation reaction were studied in order to minimise degradation due in particular to acid catalysis and to reduction of the reacting sites occurring in competition with derivatisation. Characterisation of the derivatised carrageenans by SEC-MALLS- RI was performed and showed that the extent of degradation occurring during the labelling reaction was a maximum of 40 % for kappa and 20 % for iota and lambda. The presence of the label APTS in excess and its reaction with the reagents during the labelling reaction produces peaks interfering with those from the carrageenan. A sample clean-up was therefore required before injection onto CEo A comparison was made of a range of clean-up procedures (centrifugation, dialysis, preparative SEC) to remove side products of the reaction and salts and to concentrate the carrageenans. Various seaweed extracts were analysed, including standards of carrageenans not available commercially. This study revealed that carrageenans are complex structures, and often occurring as hybrids between sUb-types. CE has the ability to characterise these hybrids, unlike spectroscopic methods which detect individual residues. When using actual food products, preliminary steps such as defatting and dialysis were found to be necessary to allow satisfactory detection of carrageenans. Finally the strategy for sample purification, derivatisation, clean-up and separation was successfully applied to additive mixtures used as raw materials in the food industry and to finished products (jelly, dairy products). CE has proved to be a fast and sensitive method to identify and provide semi-quantitative information on carrageenans present in such mixtures.

The objective was to examine the use of acetic acid (AA) with xanthan gum (XG) or konjac flour (KF) to reduce variation in cooked color of ground beef patties varying in myoglobin and pH. Beef clods were selected from carcasses of young (<24 months, Y) and mature (>48 months, M) animals. Within each age category, high (>6.0, H) and normal pH (5.3-5.7, N) clods were chosen. Ground beef was prepared from each maturity/pH combination and treatments applied at 12% of the meat block: control (mixed only), 0.5% AA, 0.25% XG/0.5% AA, or 0.125% KF/0.5% AA. Dry and moist cooking was performed in a convection oven to internal temperatures: 65.6 degrees C, 71.1 degrees C, and 76.7 degrees C. Patties were held at 76.7 degrees C for up to 240 min in dry and moist environments. Internal (assessed at 0, 120, and 240 min of holding) and external (assessed every 30 min, 0 to 240 min of holding) color evaluations (CIE L*a*b*, visual doneness, and pink scores) were conducted. Three replications were performed. The YN patties had the most done appearance internally and the highest denatured myoglobin percentage. Generally, the YH and MN patties had responses between YN and MH got most variables. The MH patties had the highest internal a* color space values, lowest degree of doneness scores and low percentage of denatured myoglobin. The YN patties responded normally to the different internal temperatures achieved during cooking. The YH, MN, and MH patties had increased doneness to 71.1 degrees C and plateaued between 71.1 degrees C to 76.7 degrees C. Visual degree of doneness decreased during moist holding and this was most evident in dry cook/moist held patties. Patties from MH meat were not affected by the treatments as much as the other meat types. The inclusion of AA, XG/AA, and KF/AA in patties made from YH and MN can effectively reduce visible redness and increase myoglobin denaturation in comparison to the control YN beef patties. These ingredients could be viable options to reduce the variation that pH or myoglobin content imparts on ground beef patty cooked color, but as seen in the MH meat, treatment additions were not effective for overcoming both pH and high myoglobin content.

Alternative methods to reduce the variation caused by pale, soft, and exudative (PSE) and dark, firm, and dry (DFD) conditions in meat tissues need to be examined. The objective of this dissertation was to determine if functional ingredients, like hydrocolloids and bicarbonates, improved the quality of PSE and DFD meat. This was accomplished by examining the rheological characteristics of meat model systems and products after enhancement with hydrocolloids and bicarbonates ingredient solutions. These results will be used to formulate and manufacture either enhanced beef steaks, beef roasts, or frankfurters to test the efficacy of use to improve the quality of DFD or PSE meat. The flow behavior, steady-shear viscosity, and dynamic testing of hydrocolloid solutions were determined. Torsion Analysis (TA) and Texture Profile Analysis (TPA) were performed on PSE muscle tissue gel samples and frankfurters. Raw and cooked CIE color space values, pH, and sensory evaluation determination were made on meat gel samples, beef steaks, roast beef, and frankfurters. Hydroxypropyl methylcellulose (1.0%HPMC), methylcellulose (1.0%SGMC), and konjac flour (0.125%KF) were found to be Newtonian in behavior. The dynamic moduli of these ingredients were resistant to changes in ionic strength and were tested for viability in a meat model system. Potassium bicarbonate (KHCO) was a viable substitute for sodium bicarbonate. The synergistic effect of combining KHCO with hydrocolloids, salt and sodium phosphate (SP) improved the color, pH, and textural properties of PSE ground pork and frankfurters, but did not effect sensory characteristics. Acetic acid (AA), KF, and xanthan gum (XG) were added to beef steaks and bottom rounds to reduce the meat quality variation caused by high pH and animal age. The addition of AA and hydrocolloid treatments improved the color and pH of high pH muscles and did not appreciable affect shelf-life flavor of cooked roast beef. Solutions of AA, KF and XG were viable enhancement treatments for use in high pH beef bottom rounds to produce a fully cooked roast beef product.

Mayonnaise is a mixture of egg yolk, vinegar, water, spices and 70-80% oil forming a semi-solid oil-in-water emulsion. When preparing a low-fat mayonnaise with an increased water content, thickening agents are required for increased viscosity and emulsion stability. The hydrocolloids xanthan gum and guar gum are sometimes used for this purpose and they act synergistically creating a viscosity increase. However, guar gum has poor acid stability, and because mayonnaise is an acidic product guar gum will eventually start to degrade causing a viscosity decrease and subsequent emulsion separation. Despite this fact, guar gum and xanthan gum are extensively used in mayonnaises today. The aim of this degree project was to explore how the synergy between guar gum and xanthan gum influences the viscosity of a low fat mayonnaise and whether high acidity will have an impact on the viscosity over a 4-week period. This was to examine if and if so, how a mayonnaise recipe can be modified to maintain a cost efficient product with the desired rheological properties in times of hydrocolloid price fluctuations. The study was conducted by preparing 15 mayonnaises with 50% fat, either at pH 3,5; 4 or 5 and a total of 0,6 % hydrocolloids with varying proportions of guar gum and xanthan gum. The mayonnaise samples were studied by measurements of viscosity, color changes and a visual comparison of their mayonnaise-like flow-properties compared to Hellmann’s Real Mayonnaise used as reference. The viscosity of the mayonnaises increased with increasing ratio of guar gum. On the other side, there were greater viscosity losses in mayonnaises with increasing ratio of guar gum 4 weeks after preparation compared to 4 days, with no apparent signs of correlation between higher acidity and hydrocolloid degradation. Mayonnaises with 20% xanthan gum and 80% guar gum had the texture most similar to the reference. In these low-fat mayonnaises, the use of more xanthan gum led to an undesired “slimy” texture and a lower viscosity – an important aspect if adjusting a low-fat mayonnaise recipe by increasing the ratio of xanthan gum. Because a commercial mayonnaise sometimes is consumed several months after manufacturing, that time frame is most likely required in order to fully measure how much the high acidity in mayonnaise will affect its viscosity. This project has shown a pattern where viscosity in the assessed mayonnaises starts to decrease a few weeks after preparation. However to find out exactly to what extent and how this would affect the overall product, and ultimately: if guar gum/xanthan gum combinations are suitable for long-term mayonnaise applications, further studies are required. / Viskositet och syrastabilitet i majonnäs med låg fetthalt och olika proportioner av xantan och guarkärnmjöl Majonnäs är en blandning av äggula, vinäger, vatten, kryddor och 70-80% olja som bildar en semi-solid olja-i-vatten-emulsion. För att tillverka en lågfettsmajonnäs med högre vatteninnehåll behöver förtjockningsmedel tillsättas för viskositet och emulsionsstabilitet. Hydrokolloiderna xantangummi och guarkärnmjöl används ibland i detta syfte och de utövar en synergi som ger ökad viskositet. Dock har guarkärnmjöl dålig syrastabilitet och eftersom majonnäs är en sur produkt kommer guarkärnmjölet efter ett tag att brytas ned vilket leder till en viskositetsminskning och emulsionsseparation. Trots detta används guarkärnmjöl och xantangummi i stor utsträckning i majonnäser idag. Syftet med examensarbetet var att undersöka hur synergin mellan guarkärnmjöl och xantangummi påverkar viskositeten i en lågfettsmajonnäs och huruvida en hög syrahalt kommer att påverka viskositeten under en 4-veckorsperiod. Detta för att se om och i så fall hur ett majonnäsrecept kan modifieras för att erhålla en kostnadseffektiv produkt om priset på hydrokolloider växlar. För arbetet bereddes 15 majonnäser med 50% fetthalt, antingen med pH 3,5; 4 eller 5 och totalt 0,6% hydrokolloider med olika proportioner av guarkärnmjöl och xantangummi. Majonnäserna undersöktes genom mätning av viskositet, färgförändringar och en visuell jämförelse av deras majonnäsliknande flytegenskaper i förhållande till Hellmann’s Real Mayonnaise som användes som referens. Viskositeten i majonnäserna ökade med ökande halt guarkärnmjöl. Å andra sidan minskade viskositeten i högre grad med ökande halt guarkärnmjöl 4 veckor efter tillverkning jämfört med 4 dagar, men inga tydliga samband mellan högre syrahalt och nedbrytning av hydrokolloider syntes. Majonnäser med en blandning av 20% xantangummi och 80% guarkärnmjöl hade den konsistens som var mest lik referensen. I dessa försök med lågfettsmajonnäser ledde användandet av högre halt xantangummi till en oönskad ”slimig” textur och en lägre viskositet – en viktig aspekt om ett recept på lågfettsmajonnäs ska modifieras genom att öka halten xantangummi. Eftersom en kommersiell majonnäs ibland konsumeras flera månader efter tillverkning så är det troligtvis den tidsramen som krävs för att helt kunna mäta hur mycket den höga syrahalten i majonnäs kommer att påverka dess viskositet. Detta projekt har påvisat ett mönster där viskositeten i de analyserade majonnäserna börjar minska några veckor efter tillverkningen. Men för att få reda på exakt i vilken utsträckning och hur detta skulle påverka produkten i sin helhet, och i slutändan: om kombinationen med guarkärnmjöl och xantangummi är lämplig för majonnäser med lång hållbarhet krävs ytterligare studier.