Variation in content of monomeric phenolics during the processing of grape seed and skin flours
2009
Sun, J. | Elena, G.G. | Peng, H.X. | Guo, Q. | Yang, B. | Zhu, E.J.
Phenolic compounds were extracted from grape seed and skin flours. Three major monomeric phenolics, gallic acid, (+)-catechin and (-)-epicatechin, were identified and quantified by high performance liquid chromatography. To evaluate the feasibility of using both flours for the development of phenolic-rich functional foods, the variation in content of these monomeric phenolics were determined after baking, illumination and microwave radiation processes. The results showed that baking both flours at 110°C had no significant influence on the contents of the three monomeric phenolics. However, after baking at 145°C, the contents of gallic acid exhibited an increasing trend, while the contents of (+)-catechin and (-)-epicatechin gradually declined. During the illumination process, the contents of gallic acid and (+)-catechin in both flours increased, while (-)-epicatechin decreased after 10 days. Microwave processing baked flours for 1 min had no significant effect on the contents of these three monomeric phenolics. After processing for 3 and 5 min, the gallic acid contents significantly increased, but the other two decreased. These results indicated that producing foods containing grape seed or skin flours should avoid being baked at higher temperatures for long periods, and the microwave radiation process should be performed as quickly as possible, so that the phenolic ingredients in these foods are better retained.
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