Optimization of Enzymatic Hydrolysis of ACE Inhibitory Peptide from Jujube Kernel

In this experiment, jujube kernel protein was extracted from defatted jujube kernel residue by alkali solution and acid precipitation, taking the inhibition rate of angiotensin converting enzyme (ACE) and degree of hydrolysis as indicators to screen the compound enzyme species. Using the response surface method, with proportion of neutral protease/alkaline protease, pH, substrate concentration, enzymolysis temperature, digestion time as test factors, the optimum enzymatic hydrolysis parameters of ACE inhibitory peptide from jujube kernel were optimized. The results showed that neutral protease and alkaline protease were selected as complex enzymes, and the optimal amount of enzyme was determined to be 6000 U/g. The order of influence of five factors on the ACE inhibition rate and hydrolysis degree was: Enzymatic hydrolysis temperature, enzymatic hydrolysis time, pH, ratio of neutral protease to alkaline protease, substrate concentration. Through the fitting equation analysis, the optimum conditions of ACE inhibition of peptidyl enzymatic hydrolysis of jujube kernel were as follows: Neutral protease/alkaline protease ratio 2.1:1, hydrolysis temperature 54 ℃, substrate concentration 3.1%, pH7.5, hydrolysis time 62 min. Under these conditions, the actual ACE inhibition rate and hydrolysis degree of the hydrolysate were (79.46%±0.49%) and (31.45%±0.85%), respectively, which were close to the theoretical values. Compared with captopril, the ACE inhibitory rate of the prepared ACE inhibitory peptide was (79.46%±0.49%), and the deviation from captopril was (19.28%±0.12%), which proved that the ACE inhibitory peptide had a significant antihypertensive effect. This study proved that the ACE inhibitory peptide could be effectively obtained by enzymatic hydrolysis of jujube kernel protein and optimized the enzymatic hydrolysis process, aiming to provide reference direction and theoretical basis for the reuse of jujube kernel residue.