Treatment technology of soy milk improving texture characteristics of lactone tofu

Abstract: Tofu is a nutritional, gel-like soy food. Its preparation generally includes soaking and grinding of soybeans in water, filtering, boiling and coagulation of soy milk, molding and pressing in the same basic methods. It is consumed in significant amounts in Asian countries like China and Japan because of their inexpensive, high quality protein. Because of its bland taste, the textural properties markedly influence its food quality and consumer acceptability. The textural properties are governed by soy milk concentration, coagulant type and concentration, gelation pressure and temperature, and gelation time. The textural properties of tofu also varied with the density of the gel network, the size of protein granules in the network from microscopic view. The particle size of soy milk was changed by some treatments to improve the texture characteristics of lactone tofu. Effect of plate gap (10-30 μm), ultrasound power (1-3 W/g) and homogenate speed (1 000-5 000 r/min) on texture characteristics of lactone tofu were studied in this article. The results showed that treatment with colloid mill significantly (p<0.05) increased elasticity and cohesion of lactone tofu. However, grinding for longer time lowered hardness of lactone tofu under the condition of plate gap of 10 μm. Treatment of soy milk for 2 min under the plate gap of 10 μm effectively improved the quality and texture characteristics of lactone tofu. Hardness and elasticity of lactone tofu all offered upgrade firstly then descending latter tendency under different intensities of ultrasound power. Cohesion of lactone tofu was decreased significantly (p<0.05) by ultrasound treatments. Treatment with ultrasound powder of 2 W/g for 3 min exhibited better quality of lactone tofu. All texture characteristics of lactone tofu showed descending following its ascending under homogenate conditions. Soy milk treated by homogenate at 1 000 r/min for 8 min was better choice. By multi-index comprehensive evaluation of Topsis, the results showed that homogenate at 1 000 r/min for 8 min was more suitable for soy milk as its improvement of texture characteristics of lactone tofu. The size of particle was shifted from 8.6 to 4.2, 1.6, 1.4 μm when soy milk treated by colloid mill, homogenate and ultrasound, respectively. The results of particle size analysis showed that the processing could reduce the particle size of soy milk, which played an improvement role in texture characteristics of lactone tofu. The texture characteristics of lactone tofu were improved by processing technology of soy milk to meet the different requires. The result can provide a reference for the processing technology of lactone tofu.