Effect of Soaking Time on the Quality of Soymilk and Their Correlation Analysis

The effects of soybean soaking time (6, 8, 10, 12, 14, 16 h) on the physicochemical properties and sensory quality of soymilk were studied, which provided theoretical support for the selection of soybean soaking time. Soybean moisture content and distribution, soluble protein content, solid content, particle size, viscosity, stability and sensory score were used as indicators to analyze the influence of soaking time on the quality of soymilk and determine the optimal soaking time of soybean. The relationships between soaking time, soybean moisture composition and soymilk quality were analyzed by using the Pearson's correlation method. The results of low-field NMR showed that with the increase of soaking time, the signal values of T₂₁, T₂₂ and T₂₃ increased, and the proportion of adsorbed water increased. The soybean moisture reached saturation after 12 h soaking. The results of the quality study showed that with the increase of soaking time, the protein transfer rate, the average particle size at volume and viscosity of soymilk had a trend of increasing first and then decreasing. The total solids content decreased significantly (P<0.05), and soymilk stability decreased first and then increased. The sensory comprehensive score first increased and then decreased, with the highest score of 1.0466 after 8 h soaking, followed by 10 h soaking. Based on the above results, 8 h was chosen as the best soaking time for soybeans to make soymilk. Despite the viscosity, the taste score and the brightness value were low after 8 h soaking, the soluble protein content was the highest, which was 0.905 g/100 g, and the protein transfer rate reached 16.61%. The total solids content was 3.185 g/100 g after 8 h soaking, which was second only to 6 h of soaking. Meanwhile, b value was the lowest, and the sensory comprehensive evaluation value was the highest after 8 h soaking. The correlation analysis results showed that the soaking time was significantly negatively correlated with the proportion of soybean bound water and free water, and significantly positively correlated with the proportion of adsorbed water (r=−0.9638, −0.8241, 0.9391). The quality index of soymilk was affected by the soaking time, which was significantly negatively correlated with the soluble protein, the total solids content and the L value, and significantly positively correlated with a value (r=−0.9122, −0.9726, −0.8238, 0.9385).