Study On The Degree Of Polymerization Of Phenolic Compounds And Procyanidins In Grape And

Phenolic compounds are commonly found in grapes and wines, and play an important part in the sensory characteristics and health promoting effects of grape and wine. The phenolic compounds of21varietal vitis vinifera (grape pulp, grape skins and grape seed) from germplasm resources nursery (Tai Gu) of Shanxi Province were investigated, and the polymeric flavan-3-ol composition of wines and skins also had been studied using fractionation on C18Sep-Pak cartridges followed by reaction with acid-catalyzed degradation in the presence of toluene-R-thiol (thiolysis). Meantimes, the absorption of phenolics of wines had been studied through the in vitro digestion method. Finally, these studies provided the theory basis for the machining of the wine as well as quality evaluation.The main research findings are as follows:(1) The determination results showed that the significant differences were detected in the phenolic compounds of the analyzed21varietal vitis vinifera. Meanwhile, the significant differences of phenolic compounds also had been observed in the different grape tissues. In relation to the total phenols, Walpole grape (grape seed), Ruby Cabernet grape (grape skin) and Seibel Noir (grape pulp) displayed the highest total phenol values. With respect to the total flavanol, Ruby Cabernet (grape skin) and Walpole grape (grape seed) contained the highest total flavanol values. The analysis of fifteen monomeric phenolics in vitis vinifera was performed by HPLC. phenol profiling varied considerably among different vitis vinifera varieties and different grape tissues. Therefore, the content and the composition of polyphenols differ, depending on grape varietal and their localization in the grape tissues.(2) Statistically significant differences were found in the mDP, the galloylation and the prodelphinidins. As regards wines, The polymeric flavan-3-ol composition showed a mean degree of polymerization (mDP) value of7.6-9.2, with Cabernet Gernischt presenting the highest values, and Merlot has the lowest values. In Contrast, Merlot presented the highest percentage of galloylation (6.0%), while Cabernet Gernischt showed lowest values (3.3%). In addition, The values of prodelphinidins are in the range between10.5%and14.9%, and the change order was consistent with mDP. In relation to grape skin, Ruby Cabernet presenting the highest values of mDP(62.5), and Pinot Gris has the lowest values(28.6). In Contrast, Ruby Cabernet and Pinot Gris showed lowest percentage of galloylation (2.1%). While Merlot presented the highest percentage of galloylation (4.5%). Moreover, The value of prodelphinidins are in the range between19.1%and29.5%. Finally, The thiolysis of procyanidins results showed that epicatechin and epicatechin-gallate were the major composition in the extension units, and catechin was the major composition in the terminal unit.(3) By in vitro gastrointestinal digestion procedure, the content of total polyphenols, total flavanols and individual phenolic of red wine were higher than white wine. At the same time, when dialyzing2h, the content of phenolics come to34%and40%of total digestive fluid, and the content of individual phenolic come to50%of total digestive fluid. In the artificial simulated gastric fluid, due to gastric acid and pepsin, with the increase of pH, the content of the total polyphenols, total flavanols and individual phenolic of four wines gradually reduce, and the proportion of dialysate also gradually reduce. In the artificial simulation intestinal fluid, with the longer duration of digestion, the content of the total polyphenols, total flavanols and individual phenolic of four wines gradually increase, and the proportion of dialysate also gradually increase. By in vitro gastrointestinal digestion procedure, with the increase of wine, the change tendency was similar to time. The in vitro digestion method is closer to the real physiological environment. and more rapid and simple.