Pre-treatment of Soy Slurry with Viscozyme L and the Concentration of Sugars and Isoflavones and the Microstructure of Silken Tofu

Silken tofu which retains soluble solids present in the soymilk was investigated for differences in the microstructure, sugars and isoflavones content from regular silken. Soy slurry treated with Viscozyme L (2.5 mL/L) was incubated for 30 minutes at 55°C. Stachyose was the predominant oligosaccharide in treated tofu, 4.58 g/100 g and 3.30 g/100 g in control tofu, raffinose content was 1.21 and 0.75 g/100 g in treated and control tofu, respectively. Glucose was approximately duplicated in treated tofu (1.66 g/100 g) compared to control (0.74 g/100 g) while fructose content was three times higher (1.09 g/100 g). Comparing isoflavones content, malonyl conjugates were double the amount of the control tofu, with the exception of malonylgenistin, but the total amount of isoflavones was not different. The tofu of the treated slurry showed a fibrous three-dimensional network structure, but with larger protein aggregates and was more tightly connected than the control.