Matrix Effects Of Polyphenol On Aroma Formation From Terpene Glycosides During Grape Juice Fermentation

Terpene glycosides（TGs）are the main origin of free terpene compounds in wines,and polyphenols are the predominate non-volatile flavor compounds in wines,so,it has strongly theoretical and practical meanings to research the matrix effects of polyphenol on aroma formation from TGs during winemaking.In this work,mimic grape juice with TGs was fermented,and catechin,gallic acid,quercetin,p-coumaric acid and tannic acid were added separately as single virable in 25%,50%,100%,200%and 300%of the concentration in young red wines（100%）.Then,the dynamic formation of free terpene compounds during fermentation and sensory evaluation of final wines were both studied,and the matrix effects of polyphenol on aroma formation from TGs were explored.The results were as follows:（1）TGs were prepared and analyzed.In this work,TGs from grape skins were extracted by Meili I（0.1 mol/L citric acid-0.2 mol/L Na₂HPO₄,p H 3.2）,Meili II（0.1 mol/L citric acid-0.2 mol/L Na₂HPO₄,12%（v/v）ethanol,p H 3.2）and Meili III（0.1 mol/L citric acid-0.2mol/L Na₂HPO₄,12%（v/v）ethanol,p H 7.0）,respectively,then purified by XAD-2 resins,and finally detected by G-G method,GC-MS and LC-MS.The G-G results showed that the total concentration of TGs were no significant difference among the three treatments.While,GC-MS results showed that Meili III had the most free terpene compounds with 414.66μg/kg,and linalool was the most abundant one,taking up 45%-48%of total contents.LC-MS results showed that the kinds of TGs with molecular formula C₂₁H₃₆O₁₀ and C₂₁H₃₆O₁₁ were the most,and the later one was also the richest ones.So,Meili III which had more kinds of the last two groups of TGs was chosen as the extraction methods.（2）Influence of polyphenol on formation dynamics of free terpene compounds during fermentation were also studied.In all,nine free terpene compounds were detected by GC-MS,namely,linalool,hotrienol,citronellyl acetate,L-α-terpeniol,geranyl acetate,citronellol,nerolidol,2,3-dihydro farnesyl acetate and farnesol.And 8,7,7,7 and 5 kinds were detected in catechin,gallic acid,quercetin,p-coumaric acid and tannic acid treatments,respectively.Except catechin,polyphenol had considerable influence on free terpene compounds,particularly,750 mg/L（300%）gallic acid could significantly promote the production of all free terpene compounds,and 750 mg/L（100%）tannic acid was better for the formation of linalool,hotrienol,L-α-terpeniol and nerolidol.While,at 250 mg/L（100%）p-coumaric acid,the contents of hotrienol,L-α-terpeniol and nerolidol were the lowest.Besides,during fermentation,gallic acid could significantly reduce the contents of nerolidol;quercetin may markably restrain the formation of hotrienol and 2,3-dihydro farnesyl acetate,and the effects for the latter one was gradually enhanced when gallic acid increased as well as the promotion effects for farnesol;p-coumaric acid could dramatically cut down the concentration of hotrienol,nerolidol and 2,3-dihydro farnesyl acetate,and its suppression effects on linalool was strengthened with its addition increased;tannic acid could notably inhibited the production of hotrienol and nerolidol,while its promotion effects for farnesol was increased when its addition enhanced.（3）Influence of polyphenols on aroma characteristics of wine were analyzed.Sensory evaluation results showed that fruity and floral aroma were the main attributes for all wine samples.Catechin,gallic acid and quercetin could significantly suppress tropical fruity and temperate sweet fruity aroma,while the suppression was declined as the polyphenol contents increased,it showed that more catechin and gallic acid（both 750 mg/L,300%）were benificial for fruity aroma,as for quercetion,it’s better for temperate acid fruity and floral aroma at 100%concentration（100 mg/L）.And p-coumaric acid and tannic acid had the best wine aroma at 100%concentration.But,p-coumaric acid could restrain tropical fruity and floral aroma,and its suppression on citrus aroma was increased as its concentration increased.While,tannic acid can inhibit tropical fruity and citrus aroma,and when its addition increased,the inhibition on tropical fruity was increased,but on citrus was declined.（4）Polyphenol effect on aroma formation from TGs were explored based on quantum chemistry method.The energy changes of single and binding compounds from gallic acid,linalool and its linalool-arabinofuranosyl-glucopyranoside（linalool-Ar-G）were calculated in this work.Results showed that gallic acid could form more stable adducts with linalool-Ar-G（ΔG=-3.83 kcal/mol）which driven by hydrogen bonds and dispersion energy.So,when addtion was low,gallic acid may bind linalool-Ar-G firstly,then,when its addtion increased and no more linalool-Ar-G,linalool would be bound gradually.It may explain the formation of linalool during fermentation and the aroma difference among final wines with various contents of gallic acid.And it speculated that other TGs in gallic acid fermention system and TGs in other 4 polyphenol fermentation systems may conclude the similar results.