Ultrasound application in winemaking

The aim of this work is study the effects produced by cavitation induced by ultrasound on different winemaking phases, in particular skin maceration, yeast lysis, color evolution and lees filterability. After some preliminary tests with laboratory equipment, an experimental design was created to optimize ultrasound conditions like time, amplitude and frequency depending on product treated and on enological objective. Tests that gave best results in the laboratory were compared to the traditional enological practices. Concerning skin extraction, best results were shown using 90% amplitude for 3-5 minutes with the frequency between 20 and 27 kHz, leading a significant increase in total phenolic compounds. Ultrasounds applied on crushed grapes before vinification reduced significantly maceration time on red grapes (up to 50%) and white grapes maceration for aroma extraction can be avoided. To evaluate the effect on yeast cell after fermentation, some trials were performed with ultrasounds on fine lees from white wines. The results showed a significant rise in yeast soluble cell compounds. This increment implies a reduction of aging period of wines on lees in comparison with conventional techniques. Recent experiences shows a significant effect of ultrasound treatment on juice and wine clarification lees that increase the tangential filtration performance in term of liquid recovery and treatment costs. Also the effect of ultrasounds on tannins and anthocyanins evolution were tested on young red wines, in order to investigate the changes during aging process. Good results were reached in each test and the use of ultrasound improve the tannin polymerization and color stability. An industrial plant was made for the winery application; the results obtained in pilot scale application in different viticulture region around the world, confirm good results for the different applications using few minutes of treatment. Technological factors (time and amplitude) must be calibrated depending on specific enological application