optimal vintage date

The specialists of UVaSens of the University of Valladolid are developing a new method of analyzing the skin of the grape to know the optimum date for the vintage.

Usually the vine growers calculate the date of vintage according to the relationship between sugars and acids in the grape, and the other determining factor in agriculture such as weather forecasts.

The University of Valladolid, and its group of chemistry, physics and engineering specialists from UVaSens, are developing a new technology that can help grape growers determine the vintage date, an important factor to obtain quality wines. It is a sensor that determines the optimal date from biomolecular information existing in the skin of the grape. Before the maturation stage, the grape changes color progressively, it is what is known as "envero", passing from the greenish-yellow color, to the red, passing through ocher tones. This process indicates that the maturity of the grape is close. From envero until the ends of maturation, the cells of the pulp accumulate water and sugars, expand, and the skin cells are affected by this expansion, producing and accumulating phenolic compounds and degrading and softening the grape.

These phenolic compounds are antioxidants of interest for the food industry, and their distribution in the skin of the grape determines the degree of maturity and the quality of the wine. With the sensor developed, biochemical changes are detected that will help us determine the ideal date for the vintage.

Three varieties of grapes from Spain were used for the study: Mencía, Prieto Picudo and Juan García and the UVaSens team had the collaboration of the Estación Enológica de Castilla y León, Instituto Tecnológico Agrario de Castilla y León (Itacyl)  and the R & D department of the Bodega Cooperativa de Cigales that provided the samples for the analysis during six weeks throughout the maturation stage and carried out chemical analyzes that served as control. The scientific team calibrated the system with the three types of grapes, given that each variety shows its own maturation characteristics.

Thanks to the use of electrode systems sensitive to electrochemical variations in the skin of the grape, the reduction-oxidation processes were calibrated. In this chemical reaction, phenolic compounds are fundamental for their antioxidant properties. In the experiment, the sensors attached to the skin showed good correlations with respect to the ideal moment of maturation of the grape.

From UVaSens indicate that the new methodology is already available for the industry, but would like to perform more checks on other varieties to improve the calibration, taking into account that in each type of grape skin phenols have a differentiated behavior.

Source: Vinetur 26 June 2018

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