Studies for the ultrasound application in winemaking for a low impact enology

IIn winemaking, although some research has been carried out, the practical application is still in an early stage. The cavitation process induced by ultrasounds leads to the breakage of the cells walls, thus facilitates the release of the cell content in the wine. The aim of this work is to study the effects produced by the ultrasound on crushed grapes, seeds, lees, and wines, in order to verify the possible speeding up of the extraction, the polymerization of the phenolic compounds, and the release of compounds from the yeast cells. After some preliminary tests, an experimental design has been created to optimize the test conditions, like time, amplitude and frequency. After different laboratory activities, recent experience in the cellar with a prototype have confirmed the possibility of using ultrasound for a short time (3-5 minutes) as a pre-treatment on crushed red grapes for the extraction of polyphenols and on crushed white grapes for the extraction of aromas. The treatment on the lees has confirmed the possibility of shortening the time of aging on the lees. Also good results have been reached in young red wines using the ultrasound to promote a positive tannin evolution. Experiences are ongoing to create an industrial plant for treatment with ultrasound in cellar, with variable flow rates between 50 and 300 hL/h; we are also being studied further applications in other stages of the winemaking process.