There is a strong link that creates a correlation between the yeasts that live in the grape at the time of collection and the typicality of the wine: the climatic conditions.
During harvest, the winegrowers follow strictly the ripening of their grapes. Its collection at the optimum point guarantees certain characteristics that will determine the sensory profile and the typicality of the final wine. But getting this status is no easy task when it comes to changing weather conditions.
During ripening of the grape, which has an average duration of 46 days, a complex process of transformation takes place in the fruit, which includes phenomena such as thickening and softening of the berry, enrichment in sugars, loss of acidity, accumulation of Polyphenolic compounds and aroma formation. As we can see, the maturity of the grape is not a concrete state, but rather a compendium of different types of maturation that ideally have to coexist so that the fruit does not harbor imbalances.
A slight change in the temperature or humidity of the area can change the profile of the grapes, altering the ripening rate and causing the acceleration or deceleration of some of the ripening types: physiological, saccharimetric, aromatic, phenological, etc. It is at this point that we introduce the concept of “microbiological ripening“, which so far has not been taken into account as a determining factor. It is necessary to discover its importance as a bioindicator of reference to determine the optimal point of harvest. It is a moment in which the fermentative species of yeasts and bacteria that live in the grape reach their maximum percentage in relation to the rest of the microbial community.
Achieving the optimum point of harvest means to pick the grape with a suitable microbiological diversity in line with the rest of ripening indicators. But can all these conditions occur at the same point? This is the great difficulty of ripening control, which, although exhaustive and precise, can be affected by the climate. How?
Several studies have explored the differences in the composition of grape yeast communities associated with geographic origin. In the article “Association between Grape Yeast Communities and the Vineyard Ecosystems” written by João Drumonde-Neves in collaboration with Ricardo Franco-Duarte, Teresa Lima, Dorit Schuller and Célia Pais, they describes how a study carried out in several areas of the archipelago of the Azores Islands finds qualitatively significant differences among the yeast communities of vineyards of several localities. These differences cause different results during the fermentation of the must by producing different metabolites in different quantities, which affects the final taste and aroma of the wine. Therefore, this study determines that the biodiversity of the yeasts in the vineyards is affected by the macro and microclimatic conditions and the geographical location of the vineyard, among others, which translates into a variation of the sensory tipicity of the wine.
Climatic conditions are a critical parameter in relation to the evolution of the maturation of the grape and can cause imbalances that will affect the sensorial characteristics of the wine. Climatic variations can cause a mismatch between saccharimetric maturation and phenolic ripening; compromising the quality of the wine from a qualitative point of view. The microbiological maturation can be compromised too by the climatological factor causing the appearance of diseases due to pathogenic fungi with the consequent loss of the quality of the grape and its health status.
Winemakers and oenologist have a really complicated task, to adjust the optimum point of harvest to different types of maturation, paying special attention to microbiological maturation and combining it with a constant control of temperature and humidity in the area. For this, it is essential to have an analysis of the microbial population in the grapes near harvest time. Discover the microbiota of your grapes with WineSeq!