EVOLUTION OF PHYTOSTEROLS IN CHARDONNAY GRAPE BERRY SKINS DURING LAST STAGES OF RIPENING

This study presents the results of rapid phytosterols analysis in grape skins during last stages of ripening. The analysis is related to the evolution of sterol content by comparison with ripening degree on two vineyards of Chardonnay grape variety in Burgundy: Meursault ler Cru and Hautes Cotes de Beaune. The characterization of sterols is realized by using combined gas chromatography-mass spectrometry from trimethylsilyl ethers of sterols. After optimization of extraction by azeotropic mixture (chloroform/methanol 2:1 v/v), the analysis allows to identify four sterols in grape skins: beta-sitosterol, campesterol, stigmasterol and lanosterol. In all the samples, beta-sitosterol is the major phytosterol (86 to 89 % of the total detected phytosterols). The evolution of phytosterols content during last stages of ripening shows a similar comportment of beta-sitosterol, campesterol and stigmasterol in grape skins: the maturation induces a loss of phytosterols in grape skins. An increase of phytosterol contents occurs at peak maturity and can be related with over-maturation phenomenon. The relationship between phytosterol content in grape skins and S/A ratio indicates a markedly negative correlation.