Antioxidant And Antibacterial Properties Of Olive Pomace Extracts And Spectral Characteristics Of Its Complex With Whey Protein

In recent years,the rich phenolic substances in olive by-products have attracted the attention of many researchers,and there are many studies on the interaction between polyphenols and whey protein.Some people also study the interaction between natural product extracts and protein,but there are few reports on the interaction between olive pomace extracts and protein.This paper mainly studied the main components of olive pomace extract and its antioxidant and antibacterial properties,as well as the interaction mechanism between olive pomace extracts and whey protein.Firstly,the extracts of olive pomace was extracted with four solvents（H₂O,50%ethanol,70%ethanol and 90%ethanol）by heating reflux method,and the components and total phenol of the extracts were determined by HPLC and GC-MS.Secondly,the antioxidant and antibacterial properties of the extracts were evaluated.Then,the effects of the extracts on the characteristics of UV,FTIR and fluorescence spectra of WPI and the antioxidant activity of WPI were studied.Finally,the interaction mechanism between extracts and WPI was speculated by studying the interaction mechanism between HT and WPI.The results showed that:1.The contents of total phenol and hydroxytyrosol（HT）in 90%and 70%ethanol extracts were higher than the other extracts.Volatile component analysis showed that H₂O extract was similar to 50%extract,70%extract was similar to 90%extract,and the contents of acids,esters and olefins were higher in the four extracts.2.The four olive pomace extracts have antioxidant activity,and the overall antioxidant level of 90%ethanol extract is higher than that of the other three extracts.90%ethanol extract has a certain inhibitory effect on the colony growth of Botrytis cinerea,and can prolong the spore germination time,affect the edge growth of hyphae,and make the hyphae thinner,shorter and dense.3.The study on the interaction between extracts and WPI showed that the extracts interacted with WPI and changed the structure and conformation of WPI.90%ethanol extract has a significant effect on the spectral characteristics of WPI.The antioxidant activity of WPI significantly was improved after interaction between the extract and whey protein,and the data of particle size and zeta potential indicated that the complex solution is relatively stable.4.The study on the mechanism of the interaction between WPI and HT illustrated that the interaction between WPI and HT spontaneously forms a complex with a binding site of about 1 through hydrogen bond and van der Waals force.Therefore,it was inferred that the interaction between WPI and olive pomace extract forms a complex with a binding site of about 1 through hydrogen bond and van der Waals force,rather than in the form of a simple mixture.To sum up,four olive pomace extracts contain phenols,and the content of 90%ethanol extract is higher.The extracts presented antioxidant activity,and the antioxidant activity of 90%ethanol extract is better than that of the other three extracts.In addition,90%ethanol extract showed some extent inhibitory on Botrytis cinerea,such as,effect on colony growth and spore germination.The extracts interacted with WPI,according to the interaction between HT and WPI,it was deduced that the complex with binding site of about 1 is formed between the extract and WPI through hydrogen bond and van der Waals force interaction.