RECENT APPLICATIONS OF ULTRASOUND IN WINEMAKING: FROM THE MACERATION TO THE WINE AGING

The ultrasound technology is an innovative technique in food production, however, in winemaking, although some research has been carried out, the practical application is still in an early stage. The aim of this work is to study the effects produced by the ultrasound on crushed red grapes, lees, and young red wines, in order to verify the possible speeding up of the skin extraction, the polymerization of the phenolic compounds, and the release of compounds from the yeast cells. Experiments were carried out in the laboratory and in the cellar with a prototype. The frequencies used are variable between 20 and 27 KHz at different amplitudes for times varying from 3 to 10 minutes. The ultrasounds has been applied on crushed grapes before microvinification; during these trials, skins have been removed from the wine after 2, 3 and 4 days and the measured phenolic compounds and anthocyanins content have shown that the ultrasounds can save up to 3 days of maceration, comparing to the traditional treatment that usually takes 5 days. Experiences on white grape in the cellar at 27 KHz, have shown interesting sensory responses and made it possible to eliminate the traditional maceration normally used for extraction of aromas and aromatic precursors. In order to evaluate the effect on the yeasts cell structure after fermentation, some trials have been performed with ultrasounds on fine lees from white wines. The results shown that the release of yeast cell compounds (colloids, proteins, and polysaccharides) was increasing mostly together with the increasing time of the treatment, and only marginally with the increasing amplitude percentage. This rapid release of cell compounds implies an acceleration of the maturation kinetic of wines on lees and it is possible to reduce by several months the period of aging. Also the stabilizing properties of ultrasounds on tannins and anthocyanins have been tested on young red wines, in order to investigate the possibility to accelerate the aging process. Good results have been reached in each test and the use of ultrasound it is proving to be available and promising technology for wine polyphenols evolution, in particular for the evolution of the tannins. Laboratory and cellar experiments allow the use of the industrial application of ultrasounds for the process of maceration of red and white grapes, for the yeast lysis and for the evolution of red wines, more applications are being studied. However, properties and features of plant equipments for large scale application have still to be defined, in order to optimize the process and the costs in industrial scale.