Using of a combined approach by biochemical and image analysis to develop a new method to estimate seed maturity stage for Bordeaux area grapevine

Abstract

Aim: The importance of phenolic maturity (depending on tannins and anthocyans) of the grape is crucial at harvest and determines the final quality of wine. The work presented here aims to characterize the evolution of phenolic maturity of seeds for 3 varieties combining macroscopic analysis and biochemical analyzes of these tannins at phenological stages of interest. Methods and results: Using R software for macroscopic analyzes have been shown that the color varies dramatically (from green to dark brown) in the two months between the bunch closure and maturity. Biochemical analysis (HPLC measurement) shows that tannins in seeds are increasing from bunch closure to early veraison and decrease after this step until maturity. Conclusion: All together these results have shown that the color variation is correlated to the tannins content in the seeds. Significance of the study: Nowadays, no easy ways of prediction of phenolic maturity are known. The aim of this work is to use these results (usually considered independently) to have an knowledge of seed level of phenolic maturity necessary without biochemical analysis to establish a date of great harvest for the most favorable conditions for the extraction of tannins required for the organoleptic quality of a wine .The originality of this work is to use the combined visual seeds and its biochemical composition in tannins (correlation established by CPA). Forward, these results will help to develop a decision support tool based on simply system to acquiring seed image easily usable by winemakers.