Effects of papain enzymolysis on the functional properties, stability and sensory quality of soy milk after thermal steam treatment

This study investigated the effects of different levels of papain addition (0.5 %, 0.75 %, 1.0 % and 1.25 %) on the functional properties, stability, and sensory quality of soy milk derived from thermally steamed soybeans. Compared with untreated samples, the contents of basic components in thermally steamed soy milk, increased after enzymolysis, along with the β-turn and random coil contents of soy milk proteins. Incorporating, 1.0 % papain significantly reduced the droplet size, enhanced the apparent viscosity, and increased the absolute ζ-potential from 21.40 to 38.45 mV. Confocal laser scanning microscopy (CLSM) and stability analyses revealed that moderate enzymolysis reduced the size of oil droplets and protein aggregates, thereby improving the stability of soy milk. Furthermore, thermal steaming reduced the beany odor of soy milk, and enzymolysis further decreased the contents of beany flavor compounds, resulting in higher sensory scores and better flavor.