Integrative grape to wine metabolite analyses to study the vineyard “memory” of wine

Abstract

Wine production is a complex multi-step process and the end-product is not easily defined in terms of composition and quality due to the diversity of the raw materials (grapes) and the biological agents (yeast and bacteria) used/present during the fermentation. Furthermore, linking what happens in the vineyard to the wine fermentation and ultimately to characteristics in the wine during ageing is often attempted in scientific studies, but clear causal relationships between factors are not easy to extract. Most wine research is therefore split along viticultural or oenological experimentation. Oenologists/yeast biologists seek direct links between the yeast fermenting a specific juice and the resulting changes in the wines, whereas viticultural studies explore treatments and their effects on grape production and berry quality parameters. If these studies indeed attempt to link back to the vineyards or the wines respectively, invariably one or more of the steps in the wine system is left unexplored, or being handled as a black box. The scientific challenge and opportunity therefore remains to study wine as a system (from vineyard to tank to barrel to bottle to glass). Our approaches in this regard will be explained by using examples from model vineyards under study where grape berries and their reactions to modulated environmental factors were studied using climatic monitoring in combination with molecular and metabolite profiling of the berries during all stages of development. These characterised grapes were then fermented into wines while continuing the detailed metabolite profiling of the juice and wine matrices. The wines were also subjected to sensory evaluations to complete the analysis of the final products. With these studies, we hope to contribute to the analysis of grape and wine active compounds in a holistic manner in order to identify correlations and predict outcomes under a specific set of conditions.