Physicochemical properties and isoflavone content of bread made with soy

Epidemiological and experimental evidence suggests that consumption of soybean products may significantly impact upon health. Bread made partially with soy represents a traditional alternative for increased soy consumption, and, if successfully formulated and well accepted, may offer an attractive delivery system for isoflavones and soy proteins. The overall objective of this research was to assess the impact of soy addition on physico-chemical properties in fresh and stored soy bread.; Addition of large amounts of soy (60%) significantly increases the bread density due to lack of gluten network formation and smaller air cell structure in soy bread. Total moisture content in soy bread (44.7%) was higher than in wheat bread (39.9%) and the distribution of water was found to be affected by soy addition. Upon storage, soy bread firmed at a lower rate (1.6 times) than wheat bread (6.7 times), which may be attributed to various factors: (1) Water distribution in the soy bread that favored easily removed bulk water pool that can act as a plasticizer throughout storage and maintain heterogeneity of the product, (2) A lack of recrystallized amylopectin, and (3) No change in mobility of liquid-like protons and a decrease in mobility of solid-like protons.; Total isoflavones were found to be stable during bread making, although their profile was largely altered. The proofing stage in bread preparation was key in the production of isoflavone aglycones in bread dough through beta-glucosidase activity with 48°C for two hours being optimal for aglycone production. Five percent almond addition was found to be an effective and economic level to enhance isoflavone aglycones in the soy bread formula.; No significant changes were found between the isoflavone content and composition in fresh soy bread and soy bread stored for 14 days, showing good stability of isoflavones in soy bread under room temperature. Therefore changes in the water distribution and starch and protein mobility during storage did not affect the amount or profile of isoflavones indicating that bread eaten even a week or two after storage will deliver the same enhanced nutrition.