Optimisation of wheat-sprouted soybean flour bread using response surface methodology

The effect of sprouted soybean flour on wheat bread was studied. Sprouting significantly increased the vitamin C content of soybean flour from 2.0 mg kg-1 to 3.25 mg kg-1. The sprouted soybean flour resulted in increased loaf volume, a firmer, spongy and more elastic loaf. However, increasing the sprouted soybean flour beyond 10% adversely affected these qualities. The loaf with 4% yeast and 5% sprouted soybean was significantly rated better in taste and general acceptability than the control. Significant differences existed (p < 0.05) in the proximate composition between the wheat-sprouted loaves and their respective controls. The addition of the 5% sprouted soybean resulted in a significant increase in protein, fibre and ash content of white bread. The quadratic polynomial regression model was adequate and acceptable at 0.05% for predicting the specific loaf volume and apparent yield stress. Response surface was saddle shaped for specific loaf volume where a maximum or minimum response is found at various combinations of the independent variables, corresponding to the optimal yeast (2.15%) and sprouted soybean flour (11.8%). Apparent yield stress value of 120 kN/m2 can be obtained from baking with yeast (2.4%) and sprouted soybean flour (10.6%).