EFFECT OF DRYING ON PHENOLIC PROFILES AND ANTIONXIDANT ACTIVITY OF LONGAN PULM

In order to investigate the composition of phenolics and the changes of their antioxidant activity during the longan drying, the content and the existing form of total phenolics , the monomer composition and the antioxidant activity before and after drying were analyzed. The results showed that the content of the free phenolics，FRAP antioxidant activity and DPPH antioxidant activity of the free phenolics were significantly decreased after the drying process（P 0.05）. while, the content of bound phenolics and FRAP antioxidant activity of the bound phenolics were significantly increased（P 0.05）. Nevertheless, no significant differences（P 0.05）were shown for the DPPH antioxidant activity of the bound phenolics .Meanwhile, the contents of monomer phenolics of epicatechin and tetramethyl catechol which were the composition of free phenolics were significantly decreased. However, the contents of gallic acid,vanillic acid,coumarate and quercetin were significantly increased（P 0.05）.Compare to the bound phenolics,the contents of syringic acid,tetramethyl catechol, vanillic acid and epicatechin were significantly increased（P 0.05）. These results indicated that the drying process had different impacts on the composition and content of phenolics of longan pulm, and also influence the their biological activity .