Date of Award
Doctor of Philosophy
Food and Nutrition
Tofu was prepared from soybean samples with calcium sulfate being used as the coagulant. Texture measurements were made using the Instron Universal Testing Machine. Percentage solids were determined in soybeans, tofu and okara. Soybean, soymilk, okara and tofu were analyzed for Kjeldahl nitrogen, crude lipid, copper, iron, calcium and phytic acid. Kjeldahl nitrogen, copper, iron and calcium were determined in whey. Recoveries of soybean protein, phytic acid and copper in soymilk were relatively high (>50%), however, the recovery of soybean iron in soymilk was lower (39%). Retention of soymilk protein, phytic acid and iron in tofu was also high (>90%), however, losses of copper in whey were substantial (37%). The composition of soybeans had a marked effect on the composition of soymilk. Thus, soybean composition is a useful indicator of the composition of soymilk prepared from those soybeans. High correlations between the same component in soybeans and soymilk were found for protein, phytic acid, calcium, copper and iron. Soymilk composition was a predictor of tofu composition for some but not all components. Soymilk levels of lipid, phytic acid and copper were significantly correlated with the same component in tofu. Soybean composition was also indicative of tofu composition for certain components, notably phytic acid, copper and iron. Components of soybeans that were found to be the best indicators of tofu texture were iron and phytic acid, which were related to tofu fracturability (r = 0.73) and elasticity (r = 0.82), respectively. The presence of these two components in soymilk was also related to tofu elasticity (r = 0.84 and 0.80) and these were the components for which correlations with textural characteristics were the highest, although concentrations of soymilk protein (positively) and lipid (negatively) were also related to tofu texture. In finished tofu, lipid was best related to tofu cohesiveness (r = 0.92) although copper (negatively), calcium and phytic acid were also significantly correlated with textural characteristics of tofu.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Mary Jane Schaefer
Schaefer, Mary Jane, "The phytic acid and trace mineral content of soybeans and their effects on tofu texture " (1986). Retrospective Theses and Dissertations. 8300.