Effect of Soaking and Roasting on the Physicochemical and Pasting Properties of Soybean Flour

The effects of soaking and roasting on the physicochemical and pasting properties of soybean flour were evaluated. Soybean seeds were soaked overnight in tap water for 0-72 h, hand dehulled, dried, and part of the sample was roasted. Roasted and unroasted soy beans were milled into flour and analyzed. The results showed that the total carbohydrates (22.8-27.9 g/100 g), the ash content (3.5-3.6 g/100 g), and the total polyphenols (0.29-0.51 g/100g) did not significantly change during both the soaking and roasting processes. However, the total proteins (35.8-46.0 g/100 g) and lipid contents (21.4-29.5 g/100 g) were significantly (p < 0.05) affected only by soaking, with a decrease in total protein and an increase in lipid contents. Phytate content (0.22-0.26 g/100 g) decreased significantly (p < 0.05) only with roasting. The tannins (0.01-0.30 g/100 g) and soluble proteins (4.0-29.0 g/100 g) significantly (p < 0.05) diminished with both treatments. There was a significant increase in the least gelation concentration (20-30 g/100 mL), a decrease in the swelling power (1.3-2.0 mL/mL), and consequently, reduction in the viscosity (range peak viscosity 18-210 cP) of the flour slurry after soaking and roasting. All these qualities-needed for producing nutritious flour for infants-highlighted the efficiency of these endogenous technologies.