| Proteins were extracted from walnut cakes after making oil and were hydrolyzed by 7 proteases of alkaline protease, neutral protease, flavourzyme, papain, protamex, trypsin and pepsin respectively, the walnut peptides were isolated and purified from the zymolytes by the treatment of Ultra-filtration and gel chromatography. The antioxidative and antihypertensive effects of zymolytes were evaluated in vitro for obtaining the high antioxidative and antihypertensive activity walnut peptide. The work will be a base for exploring the potential of walnut protein.Zymolytes obtained by single enzyme and combinations of two enzymes, the antioxidative and antihypertensive activity of zymolytes were studied. The results showed that the walnut protein by different enzyme had different antioxidative and antihypertensive activity. The walnut peptide from zymolyte hydrolyzed with 5h by alkaline protease had the highest antioxidative activity and its IC50 value of antioxidative activity was 3.23mg/mL; The walnut peptide from zymolytes with 5h by neutral protease had the highest antihypertensive activity and its IC50 value of antihypertensive activity was 0.97 mg/mL.The optimum technological conditions for making walnut peptide with highest antioxidative activity by alkaline protease was as follows: The time for hydrolysis was 5h, temperature 55℃, PH7.5,concentration of substrate was 8% and the dosage of enzyme was 3%(E:S).The optimum technological conditions for making walnut peptide with highest antioxidative activity by neutral protease was as follows: The time for hydrolysis was 5h, temperature 45℃, PH7.0,concentration of substrate was 5% and the dosage of enzyme was 3%(E:S).The walnut protease zymolytes was divided into different molecule weight range by Ultrafiltration with 30kD,10kD,3kD,1kD regenerated cellulose membranes, the content of the walnut protease zymolytes with the with mole-cule weight less than 1kD was highest.The results showed that there was no significant change (p>0.05) for the scavenging rate of DPPH of the peptides with the molecule weight between 3kD and 10kD, but the antioxidative acti-vity was the highest. However,the antihypertensive activity of walnut peptide was increased with molecular weight reducing,and the antihypertensive activity of walnut peptide by neutral protease hydrolysis was highest for the peptide with molecule weight less than 1 kD.The zymolytes by neutral protease hydrolysis with molecule weight less than 1 kD was further separated by gel filtration chromatography method and two fragments representing by peak 1 and peak 2 were obtained. The second fragment representing by peak 2 has the smaller molecule weight. The result showed that the inhibition rate of angiotension converting enzyme (ACE) was higher, its IC50 value was 0.25 mg/mL. |
