Study On The Condensation Of Proanthocyanidins And Its Properties In Wine System

The aim of the study was to investigate the effect of different conditions on the reactionbetween acetaldehyde and (+)-catechin that was mainly the major flavan-3-ols of grape skinproanthocyanidins using reversed phase high performance liquid chromatography.Furthermore, grape skin proanthocyanidins as raw material prepared four different meandegree polymerization (mDP) fractions through solvent precipitation. The relationship ofantioxidant activities and astringency of the four fractions has been presented. Detail researchcontents were as following.The results showed that the decrease of (+)-catechin content with time followed thefirst-order kinetic, which was in agreement with the previous study. The condensation rateincreased with the promotion of the reaction temperature and initial concentration. In addition,the kind of aldehydes affected the reaction obviously; the rate from high to low was in turn asfollows, acetaldehyde, furfural, and vanillin. By the ESI-MS analysis, in a negative ion mode,three model systems contained various polymers, up to tetramer. Results showed that thealdehydes induced condensation reactions had the same pathway. The condensation between(+)-catechin and acetaldehyde was apparently enhanced by pulsed electric field (PEF)treatment. The condensation was increased with increasing PEF intensity and reactiontemperature, as well as with decreasing pH values. Moreover, it was demonstrated that theactivation energy (Ea) of the condensation reaction was reduced remarkably by PEF treatment(from41.59kJ/mol to28.98kJ/mol below40kV/cm). However, it was seen that ultrasonictreatment did not enhance the (+)-catechin-acetaldehyde condensation reaction.The condensation reaction (+)-catechin-furfural/acetaldehyde/vanillin in model wine asstudy object, the effects of only the condensation reaction on color were studied by usingWSF. Results demonstrated that the reaction rate of (+)-catechin-acetaldehyde is faster thanthat of (+)-catechin-furfural/vanillin. With the increasing of polymerization degree, thechroma rise rapidly in model wine. The chroma of (+)-catechin-furfural were higher than thatof (+)-catechin-furfural significantly.Using grape skin proanthocyanidins as raw material prepare four fractions through solventprecipitation. The mDP of fractions was from low to high in turn by spectrophotometricmethod and circular dichroism spectrum analysis. The capability of scavenging sodium nitriteand DPPH· were determined by spectrophotometry, and compared with vitamin C, BHT. Theresults demonstrated that the scavenging rate of NaNO2and DPPH· showed the positivecorrelation with the concentration of the grape skin proanthocyanidins, the capability of scavenging NaNO2and DPPH· was94.61%and92.56%, respectively. It was explored thatwith the increase of polymerization degree, the capability of scavenging decreases.Grape skin procyanidins and protein as study object, effects of protein kinds, concentrationratio, pH value, alcohol content, and mDP on the reaction between PAs and protein bynephelometry were discussed. Protein reaction with PAs has certain selectivity. pH valuesaffected turbidity value obviously. The turbidity value was first increased and then decreasedwith increasing pH values. At about3.5, the turbidity value arrived maximize. Moreover,when the pH value above3.0, the turbidity value was first increased and then decreased withincreasing alcohol content. When the pH value was below3.0, the turbidity value appearedstable with increasing alcohol content.