Study On The Preparation And ACE Inhibitory Activity Of Pea Peptides

Field pea protein resources in China are abundant and the price of peas is cheap.However the amino acids are basically in the form of aggregation in proteins, whichseriously affect the absorption by the human body and the application of the proteins.At present, most domestic manufacturers of field pea processing focus on the peastarch extraction and ignore the development of proteins. As the result the resource offield peas has been wasted since the remaining protein materials were usually used aslivestock feed or even discarded. In order to improve the performance and nutritionalavailability of pea proteins, protease could be used to hydrolysis the proteins to obtainthe peptides biological activities.In this research, pea proteins were used as raw material, and three different kindsof proteases were selected to study the enzymolysis on the proteins. The optimumprocessing conditions of protease hydrolysis of pea protein were determined:(1) thealkaline protease: with enzyme concentration6%, the substrate concentration3%, thetemperature of55℃, pH8.0;(2) neutral protease: enzyme quantity7%, the substrateconcentration7%, temperature50℃, pH7.0;(3) papain: enzyme quantity5%, thesubstrate concentration3%, the temperature of55℃, pH6.5. By comparing therelationships between the degree of hydrolysis and the ACE inhibitory activity,alkaline protease was found to have highest ACE inhibitory activity and used as theprotease for the further study.The process for preparing the protein peptides with high ACE inhibitory activitieswas optimized by single factor tests and response surface design. The optimumprocess conditions were: Enzyme quantity6%, the substrate concentration6%,temperature53.9℃, pH8.22. Under this conditions, the ACE inhibitory rate was36.02±0.48. And the stability of the peptides obtained was further studied, it wasfound that the ACE inhibitory peptides showed strong resistance to pepsin and trypsindigestion. Hence ACE inhibitory peptides produced in this study showed goodbiological activity.Uultrafiltration technology was further used for peptide fractionation, and the optimal conditions of ultrafiltration for the hydrolyzed peptides solutions wasdetermined: operating pressure is0.14MPa, material liquid concentration is2%~3%,ultrafiltration cycle for60min. After comparing ultrafiltration grading ACEinhibitory activity of the peptides with different molecular weight, it was found that,with the increase of molecular weight, ACE inhibitory activity of each composition isdecreased. The peptides with molecular weight less than1000was collected byultrafiltration and its molecular weight distribution is measured by high-performanceliquid chromatography (HPLC). The fraction with MW300~500componentaccounted for60.39%, which means this fraction mostly contain2~4amino acidsresidues. It confirms that pea peptides with smaller molecular weight were found tohave better ACE inhibitory activities.