Study On Preparation Process And Activity Of ACE Inhibitory Peptides From Oyster

Oyster is rich in resources and has high nutritional value.Its extracts have biologica l activities such as lowering blood pressure,lowering blood sugar and antioxidation.In t his study,there were four aspects of Oysters studied,including preparation,antihypertensiv e activity,product modification and pilot production.The main results were as follows:(1)The optimum preparation process of ACE inhibitory peptide from oyster was optimized with ACE inhibitory activity,according to the preset technological process.The results showed that desalination and pre-cooking could improve the ACE inhibitory rate of oyster polypeptide,and secondary enzymatic hydrolysis could not only increase the yield of oyster polypeptide,but also increase the ACE inhibitory activity;After ultrafiltration,oyster polypeptide with molecular weight less than 3KDa showed the greatest ACE inhinitory activity.The basic components and amino acid content of the prepared oyster polypeptide were determined under the optimum process.The results showed that the polypeptide content of the oyster ACE inhibitory peptide was 66.7%,the sugar content was 18.2%,the ash content was 6.31%,and the 17 amino acid compositions were good.(2)Spontaneously hypertensive Rats(SHR)were fed with oyster ACE inhibitory peptide less than 3KDa for 28 days to evaluate the antihypertensive effect.The results showed that the systolic blood pressure(SBP)of SHR in oyster ACE inhibitory peptide group was significantly lower than that in control group except the second day.On the 21 st day,the systolic blood pressure of SHR heart decreased to(161.56 ±16.63)mm Hg.Afterwards it remained stable and was significantly lower than that in the blank group(P < 0.01)..At the same time,the ACE inhibitory peptide of oyster had the effect of inhibiting the weight gain of SHR(P < 0.05).The relative indexes of RAS and Antioxidant system in SHR serum were determined by ELISA test kit to study the blood pressure lowering mechanism of oyster ACE inhibitory peptide.The results showed that oyster ACE inhibitory peptide may reduce blood pressure by reducing the production of ANG II and reducing the content of ALD.At the same time,the oyster ACE inhibitory peptide did not cause damage to the SHR.(3)Using the ACE inhibition rate and the amount of free amino acid reduction as indicators,The enzymatic hydrolysis product was modified by Plastein reaction using the neutral protease as the enzymatic hydrolysis.The optimum substrate mass fraction,enzyme amount,temperature and time of the Plastein reaction were screened by single factor experiments.The optimal conditions were substrate mass fraction of 45%,neutral protease addition enzyme concentration of 3%,enzymatic hydrolysis temperature of 60?,and reaction time of 2 h.The comparison of free amino acid content before and after the Plastein reaction showed that plastein reaction can integrate hydrophobic amino acids into oyster peptides,thus increasing the ACE inhibition rate.(4)The pilot scale-up test was carried out on the preparation process of the small-scale test.High activity oyster ACE inhibitory peptides were prepared by ultrafiltration-nanofiltration combined with improved pilot-scale process.The results showed that the activity and purity of oyster ACE inhibitory peptide produced by pilot production were basically the same as that of small scale sample,which indicated that this process could be used in the industrial production of oyster ACE inhibitory peptide.