The Vine and Wine Research Institute of the University of León (ULE) has initiated a novel area of study on the modulation of the alcoholic strength of musts at the time of the harvest by the application of hormones. This research has great potential as alcoholic strength is an essential parameter in the production of wine not only from a business viewpoint but is also associated with numerous organoleptic characteristics and in short with its quality.
 
As DiCYT has been informed by the director of the Vine and Wine Research Institute, Enrique Garzón Jimeno, a large number of environmental factors condition one of the key processes in the production of the wine: the ripening of the grapes. One of the stages of this ripening cycle is the so-called veraison, in which a series of metabolic processes such as photosynthesis or the accumulation of organic acids slow down, while others such as the accumulation of anthocyanins (red, violet, and blue pigments depending on the variety that forms on the skin of the grape) begin, changing the colour of the grapes.
 
The veraison process, which takes place in summer, is determinant because it allows the calculation of the time of the grape harvest, depending on the variety and the climatic conditions where the plant is grown.
 
According to the researchers, despite the efforts of the scientific community in the studying of the physiological processes that take place in the grape from the veraison until the time of the harvest, there are still many questions to be answered on this critical period of the annual productive cycle of the vine.
 
It has been known for some time that hormones have the capacity to modulate the development of plants by means of complex systems”, the researcher explains, adding that the effect of the various hormones during the ripening of the grapes is not only of scientific interest but “may also be interesting for both vine growers and wine cellar (bodega) owners as they allow the bringing forward or the delaying of the ripening of the grapes by modifying their qualitative parameters and consequently those of the wines”.
 
In this way interesting aspects of current viticulture such as the controlling of sugar levels at the time of harvest (which are the precursors of the alcoholic potential of the wines obtained) can be regulated by means of the “rational” use of these hormones.
 
In this field the Vine and Wine Research Institute of the University of León has initiated a study of the control procedures of the probable alcoholic strength of musts at the time of harvest in collaboration with Bodegas Valbusenda from the Toro denomination of origin. Among these procedures the team of researchers has tested the judicious use of phytohormones or hormones of plant origin.
 
He explains that phytohormones “are a set of regulators of the development of plants, which among other functions coordinate the ripening of the grapes and changes in the expression of genes which are of great importance in the regulation of the ripening processes”.
 
The test consisted of the application of phytohormones at certain intervals in the phenological state of veraison, with the objective being the assessment of its impact both on the sugar levels of the grapes when they are collected and on the remainder of the habitual control parameters during the harvest period (the pH, total acidity, and weight of the grapes).
 
The results obtained in these initial experiments have been “promising” according to the director of the Institute, which suggests their potential use on a vineyard handling scale.