Study of different extraction methods on bound phenols in apple pomace

The bound phenols in the apple pomace were released by alkaline degradation,acid degradation,and enzymatic hydrolysis respectively,and the degradation conditions were optimized using single factor experiment.The HPLC- DAD method was applied to detect the types and contents of individual phenolic in free phenol and three kinds of bound phenols.The optimum alkaline degradation time was 4 h,and the Na OH concentration was 3mol / L,and the optimum acid degradation time was 15 h,and the methanol / concentrated sulfuric acid concentration was 13∶ 1( v / v),and the optimum enzymatic degradation time was 24 h,and the tannase activity was1000 U. Hyperoside,chlorogenic acid,phlorizin,catechin,quercetin,phloretin and gallic acid were the major polyphenols of apple pomace.Catechin,quercetin,phloretin,gallic acid,protocatechuic acid and caffeic acid were mainly in bound form. The highest content of gallic acid,protocatechuic acid,caffeic acid and phloretin by enzymatic hydrolysis were 16.122,18.574,13.030 and 69.934 μg / g respectively,and the highest content of catechin and quercetin by acid degradation were 148.909 μg / g and 66.396 μg / g respectively. Acid degradation and enzymatic hydrolysis were more suitable than alkaline hydrolysis for the extraction of bound phenols of apple pomace.