3. Results and Discussion
3.1. Effects ofenzyme hydrolysis parameters on the yield of protein and oil bodies
The extraction rate of protein reached maximum value (88.69%) at 1:2 solid- liquid ratio, but decreased and tended to level out as the ratio increased (Fig. 1a). Such a trend could be attributed to gradual dissolution of water-soluble whey protein and salt-soluble arachin and conarachin with the increase in the solid-to-liquid ratio until reaching the threshold at which arachin and conarachin were non-degradable due to their stable spatial structure (XU, LIU, & SHI, 2016; LIU, ZHAO, & SU, 2013). The yield of oil bodies increased and then decreased; it reached the maximum (42.37%) at the solid- liquid ratio of 1:4. The increase in the aqueous solution promoted the decomposition of peanut cell wall structure, but further increase in the solid-liquid ratio reduced the enzyme activity, resulting in decreased yield of oil bodies. The yield of both protein and oil bodies initially increased and then decreased, with both reaching maximum levels (68.45% and 39.28%, respectively) at the enzyme concentration of 1.25% (Fig. 1b). Increasing the enzyme concentration to a certain level increased the degree of cell wall damage and allowed that protein and oil bodies were released in the cell at a relatively stable rate. The efficiency of enzyme hydrolysis is highly dependent on temperature. The effect of different enzyme hydrolysis temperature on the yield of protein and oil bodies is shown in Fig. 1c. The protein yield decreased after an initial increase, reaching maximum levels (78.86%) at 55 °C. The yield of oil bodies followed the same trend, but reached the maximum (38.86%) at 50 °C. The protein yield reached maximum levels (79.91%) at 80 min, whereas the yield of oil bodies started increasing at 20 min and plateaued at 80 min (Fig. 1d). The rate of enzymatic hydrolysis was increased fast initially as the enzyme bound with the substrate. However, as the reaction progressed, the concentration of the substrate and the reaction rate decreased, and the yield of protein oil bodies stabilized.