Effects of soybean protein composition and processing conditions on silken tofu properties

Texture and water holding are important for silken tofu manufacturers and are affected by many factors, including soybean variety and processing conditions. In this study we evaluated these two key quality attributes of silken tofu produced from two soybean varieties - Bunya and Cowrie - using a soak or a dry processing method with glucono-δ-lactone or nigari as coagulant at concentrations of 1.5-5.0 g kg⁻¹.

The soak method produced substantially firmer silken tofu with either coagulant. The optimum coagulant concentration to achieve maximum hardness was 2.5-3.0 g kg⁻¹. At 3.0 g kg⁻¹, Bunya produced silken tofu with firmer texture for each of the coagulant-method combinations and lower water loss, an indicator for water holding capacity, for the soak method. The two varieties differed significantly in the composition of major protein subunits for the seed and soymilk. Bunya had no 11SA4, less 11S and more 7S and therefore a lower 11S/7S ratio.

Both variety and processing conditions affect textural properties and water loss of silken tofu. The absence of 11SA4 and subsequent protein subunit compositions are important in determining these two key quality attributes. Variety Bunya produces silken tofu with firmer texture and lower water loss.