Effect of Soybean 7S Protein Fractions, Obtained from Germinated and Nongerminated Seeds, on Dough Rheological Properties and Bread Quality

Germinated soybean flour has been proposed for use in bread making as a product to improve bread quality when small amounts are added to wheat flour. However, it is not clear which soybean components promote this action, and how these components may influence bread quality. The aim of this work was to evaluate the effect of the addition of soybean 7S protein fraction obtained from germinated and nongerminated seeds in dough rheological properties (farinographic and extensographic) and bread quality, including loaf volume, texture (firmness, compression force, resilience), colour (L*, a*, b*), crumb grain structure (cell density, mean cell area, shape factor), and consumer acceptance (sensory analysis). Results showed that this protein fraction just slightly affects bread quality, since no significant changes (P > 0.05) on bread volume and texture were obtained. Only crust and crumb colour were affected in a small amount, and a coarser crumb structure was also observed when adding 7S protein obtained from germinated soybean at its highest concentration. As the proportion of protein increased in the flour, both kinds of 7S fraction (germinated and nongerminated) were related to the increment in water absorption, as well as to the increment in extensographic maximum resistance to extension, specifically when adding 7S protein obtained from nongerminated soybean seeds. These results showed that the 7S soybean protein, as obtained in this work, is not related to the reported loaf bread quality improving effect of this legume when it is added in small quantities.