Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

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Alpha (α-) tocopherol is the most active component of vitamin E and is a highly desirable and heritable trait in soybean seed. The objectives of this study were to identify and validate regions of the soybean genome that correspond to tocopherol accumulation in seed. A mapping population (07-225) of 190 RILs was derived from a cross between Keszthelyi A.S. x 2355RR which identified that α-tocopherol expression in soybean seed was strongly associated with the Satt381 – Satt196 region of chromosome 9 (LG K) in lines with Keszthelyi A.S. in their pedigree. Two other F4:5 validation populations derived from the crosses Keszthelyi A.S. x PRO 2995R (population 07-223; 94 RILs) and Keszthelyi A.S. x 2355RR (population 07-226; 45 RILs) were used to validate QTL in literature. The markers Satt079 (Ch 6; LG C2), Satt440 (Ch 20; LG I) and Satt381 (Ch 9; LG K) were significantly associated with α-tocopherol expression in these populations. / OMAFRA Food Program, Grain Farmers of Ontario, CanAdvance, Hendrick Seeds

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Oil-bearing plants are important sources of edible oil and proteins; they have attracted attention recently because of their antioxidant, antimicrobial and anti-inflammatory properties. The objective of this work was to investigate the nature of phenolic compounds in oil-bearing plants and the effects of phenolic compounds on protein isolates from soybean and flaxseed. Proteins were isolated from full-fat and defatted soybean and flaxseed using sodium hydroxide extraction and isoelectric precipitation. Free phenolic compounds were extracted from the oil-bearing plants and protein isolates using methanol; for bound phenolic compounds the oil-bearing plants and proteins were subjected to basic and acidic hydrolysis followed by methanol extraction. Total free and bound phenolic compounds were determined by spectrophotometric analysis. Reversed phase-HPLC was used for separation of individual phenolic compounds, which were identified by mass spectrometry (MS). Molecular characteristics and biological properties of the protein isolates were studied using RP-HPLC, polyacrylamide gel electrophoresis (PAGE) and MS. Thermal and gelation properties of protein isolates were investigated using differential scanning calorimetry (DSC) and rheometry. Generally, bound phenolic compounds (20%-30% of total phenolic content) were higher in protein isolates from flaxseed than in protein isolates from soybean (10%-20% of total phenolic content). With flaxseed protein isolates, removal of phenolic compounds showed little effect on the electropherotic behavior of the proteins or the protein subunits. Native-PAGE. SDS-PAGE and RP-HPLC for the peptides profiles of hydrolyzed protein isolates from both full-fat and defatted soybean revealed the removal of free and bound phenolic compounds affect on the biological properties of protein isolates. Removal of free and bound phenolic compounds affected the thermal stability and gelation properties of protein isolates from flaxseed and soybean.

Full-fat soybeans require heat treatment to denature trypsin inhibitors which interfere with proper digestion of the soybean protein. This study examines the heat treatment of soybeans in a continuous particulate-medium conduction processor. / Whole soybeans at 13% and 23% moisture were roasted at salt temperatures of 225, 250 and 275$ sp circ$C for residence times of 15, 30 and 60 seconds. The soybeans reached temperatures ranging from 107$ sp circ$C to 134$ sp circ$C, after which they were maintained in an insulated container for 0, 5, 10 or 15 minutes. Salt temperature, residence time, and moisture content were found to significantly affect final temperature, temperature change, moisture loss and total heat transfer. Moisture losses in the processor were very high, indicating that combining the processes of heat treatment and drying may provide a high combined efficiency. / Analysis of trypsin inhibitor activity and soluble protein indicated that all three factors likely affect soybean quality, and the soybean quality achieved in these tests is likely to be sufficient for livestock feeding, although this remains to be confirmed through feeding trials.

The effect of infra-red heating (micronization) on the composition and textural properties of full-fat soybeans and its product (soy isolate, soymilk and tofu) were investigated. There was little difference in the overall proximate composition between the micronized and processed soybeans. Yield, protein content and textural properties of tofu made from micronized beans using standard procedures (70$ sp circ$C and CaSO$ sb4$.2H$ sb2$O as coagulating agent) were lower than those of tofu from unprocessed beans; tofu prepared from micronized beans and coagulated at 90$ sp circ$C using a mixture of citric acid (0.01M) and calcium sulphate (0.03M) showed improved characteristics. The microstructure of tofu prepared from micronized beans lacked the regularity of honeycomb-like structure as shown by tofu from unprocessed beans. / Functional, biochemical and nutritional properties of the micronized soybeans, soy isolate, soymilk and tofu were studied. The results indicate the following: the digestibility of micronized soybean (84.3%) was higher compared to the unprocessed soybean (76.5%); the available lysine content of soy isolate, soymilk and tofu from micronized soybeans were higher than the corresponding products derived from unprocessed beans; the unprocessed soybean flour displayed maximum foam capacity at pH 9.0 while the micronized soybean flour showed no foam capacity at pH 3.0 and 5.0; polyacrylamide-disc gel electrophoresis showed that heat treatment by micronization had little effect on the protein constitution of the soybean and on the protein-carbohydrate interaction but induced some interactions of protein and lipid components in the soybeans.

A laboratory assessment and three in vivo trials were conducted to measure the nutritive value of whole soybeans subjected to various methods of heat treatment. No significant differences were found for ADG and feed conversion ratio. There was a significant reduced proportion of saturated-to unsaturated fatty acids in the loin eye area of pigs fed whole soybean products, when compared to soybean meal control. Extruded whole soybeans resulted in a lower degree of unsaturation than the other heat treated whole soybeans. Whole soybean products were evaluated for their digestibility in weanling (21 days) piglets. Feces were collected daily during two 5-day periods. It was found that the ether extractable portion of extruded whole soybeans has a higher digestibility than that of the remaining four soybean treatments. It was also found that CP is more digestible in animals at 6 weeks of age than in animals at 4 weeks of age. In conclusion: heat treated whole soybeans do not adversly affect the performance of weaners nor that of growing and finishing pigs, even at high dietary levels (25%). Feeding whole soybeans results in a higher degree of unsaturation in the carcass. The EE fraction of extruded whole soybeans is more digestible than whole soybeans of other heat treatments. (Abstract shortened by UMI.)