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.