engleski

Influence of enological treatments on the phenolic content in white wine

The composition and concentration of phenolic compounds in wine depend on the grape variety, the enological treatments applied during wine-making and the chemical reactions that occur during the aging of wine. Maceration is the wine-making process where the aroma and phenolic compounds are extracted from the grape skins, seeds and stems into the must. However, extracted phenolic compounds are susceptible to oxidation reactions, thereby causing browning of white wines. Oxidative stability of white wines could be enhanced by adding glutathione, a powerful antioxidant which interferes with oxidation mechanism by trapping phenolic quinones and therefore limiting must and wine browning. The aim of this research was to determine the effect of prefermentative maceration and glutathione addition during bottling on the concentration of phenolic compounds in white wines. Samples, submitted to analyses, were: musts after clarification, wines after alcoholic fermentation and wines after 3 months ageing in bottles with addition of glutathione. Total phenolic content was analyzed by Folin-Ciocalteu method, while hydroxycinnamic and hydroxybenzoic acids were determined by high performance liquid chromatography (HPLC) with photo diode array detection (PDA). Compared with direct pressing of grapes, maceration increased the levels of total extracted phenolic compounds in musts and wines. Among analyzed phenolic compounds, macerated samples showed higher concentrations of gallic and vanillic acid and hydroxycinnamates, mainly caffeic, caftaric and coutaric acid. However, concentrations of p-coumaric and ferulic acids were higher in control samples. During alcoholic fermentation total phenolic content decreased, but concentrations of individual analyzed compounds increased which indicates loss of some other phenolic compounds, such as flavonoids. Glutathione addition, after 3 months ageing, resulted in higher concentrations of vanillic, syringic and coutaric acid in control wine samples, while higher concentrations of vanillic acid were determined in macerated samples.

Glutathione; maceration; phenolic compounds; white wine

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