Research On Preparation Of Phenolic Compounds From Hazelnut Nuts And Its Antioxidant And Antibacterial Activities

Hazelnut is a common nut around us,most of which is fried.The baked hazelnut kernel is full of fragrance and mellow taste.Hazelnut is rich in nutrients,such as oil,protein,sugar,starch,vitamins and minerals.In addition,it also has a variety of functional components,one of which is polyphenol.The results showed that polyphenol had antioxidant,bacteriostatic,antitumor and other activities,but there were few studies on the functional components of hazelnut in China.The deep processing of hazelnut in China is still in its initial stage,with low utilization and shallow excavation.This study mainly studied the preparation technology,type and content of antioxidant,bacteriostatic,antitumor and other activities of wild hazelnut polyphenol in China,in order to provide theoretical basis for the development of hazelnut functional food and the improvement of medicinal value.Taking corylus hazelnuts collected from Tieling City,Liaoning Province as experimental materials,ultrasonic assisted extraction method was used to explore the effects of ultrasonic power,ethanol concentration,solid-liquid ratio and extraction time on the extraction amount of polyphenol in hazelnut kernel in this study.On the basis of single factor,the optimum extraction conditions of hazelnut polyphenol were obtained by four-factor and three-level experiments: the maximum extraction amount of polyphenol is 0.42 mg/g when the ultrasonic power is 240 W,the concentration of ethanol is 65%,the ratio of materials to liquid is 1 to 60,and the ultrasonic time is 100 min.After repetitive experiment,the extraction amount of polyphenol was 0.43 mg/g.The components of different forms of phenolic acids(including free type,free ester type and binding type)of two kinds of hazelnut(corylus hazelnuts,hybrid hazelnuts)were determined and compared by UPLC-MS/MS.A total of 13 kinds of phenolic acids were identified,which are 3,4-dihydroxybenzoic acid,4-hydroxybenzoic acid,gallic acid,syringic acid,neochlorogenic acid,catechin,epicatechin,vanillic acid,p-coumaric acid,erucic acid,ferulic acid,isoferulic acid,salicylic acid,respectively.The highest content of total phenolic acid in corylus hazelnuts and hybrid hazelnuts was vanillic acid,and the contents of other components were obviously different.The total amount of phenolic acid in corylus hazelnuts was 33.50 g/kg,while the total amount of hybrid hazelnuts was 21.53 g/kg,the former was significantly higher than the latter.The polyphenol of the kernels in corylus hazelnuts were separated into bound phenol and free phenol by alkali hydrolysis.The antioxidant capacity of free phenol and bound phenol was evaluated by calculating and comparing the ic50(50% inhibitory concentration)value.In the removal experiment of DPPH,the ic50 value of free phenol was 2.09,and the ic50 value of combined phenol was 4.89.It was found that the scavenging efficiency of free phenol in DPPH was stronger than that of combined phenol.In the removal experiment of ABTS,the ic50 of free phenol was 5.78,the scavenging ability of combined phenol on ABTS was not obvious,and the IC50 value could not be calculated.The removal efficiency of ABTS was stronger than that of binding phenol.In terms of total reduction power,the absorbance of free phenol was 1.53 when the concentration of free phenol was 6.00 mg/mL.While the absorbance value of bound phenol was 0.93 when the concentration of bound phenol was 6.00 mg/mL.It was found that the total reduction ability of free phenol was stronger than that of bound phenol.By comparing the scavenging efficiency of DPPH,the scavenging efficiency of ABTS and the total reduction ability,the antioxidant capacity of free phenol was better than that of bound phenol.Finally,the bacteriostatic effects of free phenol and bond phenol on four bacteria and one fungus were determined by filter paper method.The results showed that the two kinds of phenol had inhibitory effect on staphylococcus aureus,bacillus subtilis,escherichia coli and pseudomonas aeruginosa.The inhibitory effect of free phenol on Staphylococcus aureus was obvious,and the inhibitory effect of combined phenol on pseudomonas aeruginosa was better.However,the inhibitory effect of the two kinds of phenol on candida albican was not obvious.Because hazelnut free phenol has no bacteriostatic ability against candida albican,four kinds of bacteria were treated with hazelnut free phenol,and it was found that the growth rate of bacteria was slowed down to a certain extent.Among them,the growth rate of staphylococcus aureus slowed down the most obviously,which further proved its bacteriostatic effect.In summary,we studied the extraction process of hazelnut phenol,the determination of phenolic acid and their antioxidant and bacteriostatic activities.The results provided basic data and technical reference for the comprehensive utilization of hazelnut resources and the development of edible and medicinal value in China.