| Grape seed is the waste of wine industry. Making good use of grape seed, will not only avoid environment pollution, but also increase the benefit of wine industry. Grape seed extract has efficient function for health keeping. As for the extraction of grape seed polyphenols, traditional solvent extraction needs long time and the extraction efficiency is low. Because of the high demand of equipments, UAE and supercritical CO2extraction are not often used in the industry. MAE efficiency is high and extraction time is short, which makes it suitable for the application in industry. There are only few studies concerned the MAE of grape seed polyphenols, and most of them ultilized the microwave oven to supply the microwave. But no one has utilized a formal microwave extractor and a proper experiment design to optimize the best condition of MAE of grape seed polyphenols. This study utilized microwave extractor and Central Composite Rotatable Design to optimize the best extraction condition of MAE of grape seed polyphenols, compared the effect of MAE and UAE of grape seed polyphenols, and studied the characteristic of grape seed extracts of MAE and UAE. Main concolusions are as follows:1,Best extraction condition has been optimized, and response surface plots of MAE of grape seed polyphenols have been modeled.Best extraction condition and optimized maximum level of TP content,280nmGAE,260nmTAE,320nmCAE have been achieved. Best extraction condition for TP is ethanol/water47.2%, liquid-solid radio45.3:1and time4.6min. TP content of the extract which was extracted with the best extraction condition is96.25mg GAE/g GS, which is about the same with optimized maximum content96.79mg GAE/g GS.2nd-Order polynomial equations and response surface plots of TP content,280nmGAE,260nm AE,320nmCAE and yield have been gained.2nd-Order polynomial equation for TP content is:y=2.013Xi+1.688X2+6.906X3-0.020Xi2-0.758X32(P=0.005)。2,With the same extraction condition, the effect of MAE of grape seed polyphenols is much better than UAE.This study has compared the effect of MAE of grape seed polyphenols,short time UAE of grape seed polyphenols (UAE-1) and long time UAE of grape seed polyphenols (UAE-2). MAE and UAE-1have the same extraction condition. TP content of UAE-1extract is much less than that of MAE and UAE-2extract. Yields,280nmGAE content and260nmTAE content in UAE-2extract are the highest, while in MAE extract is less, and in UAE-1extract is the least. With the same extraction codintion, effect of MAE is much better than UAE-1.3,Content of polyphenol monomers in grape seed extracts, color and antioxidant ability of extracts have been obtained.(1) Total monomer content in veraison grape seed extracts is higher than that in harvest. Total monomer content in Cha-ver extract is the highest. Epicatechin gallate content in Sau-ver extract is the highest. There is no benzoic acid in UAE-2extracts.(2) Extracts of veraison is much clearer than that of harvest. Extracts of harvest is redder, darker and got more yellow color than that of harvest. Extracts of red varieties is redder and darker than that of white varieties. Clarification levels gradually reduce from MAE, UAE-1to UAE-2extracts. Red and yellow color and total color levels gradually increase from MAE, UAE-1to UAE-2extracts. Difference of clarification, red and yellow color and total color between MAE, UAE-1and UAE-2extracts is highly significant.(3) Difference of antioxidant ability between8samples is highly significant. The antioxidant ability of MAE and UAE-2extracts is about the same, and both are bigger than that of UAE-1. Antioxidant ability of Chardonnay extracts is the highest, while Shiraz is the lowest.(4) The liner relationship between antioxidant ability (including the antioxidant capacity measured by FRAP and DPPH-methods) and TP content, total monomer content, catechin content, epicatechin content, epigallocatechin content, epicatechin gallate, gallic acid are all positive correlation. |
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