Effect of high intensity ultrasound on yeast of Brettanomyces genus and sensory quality of wine

Brettanomyces/Dekkera yeasts are commonly found in all vineyard regions worldwide, and are well known as wine spoilage microorganisms. They produce off-flavors (barnyard-like, pharmaceutical, burnt plastic and mousy off-flavors) volatile acids, which degrade the quality of wines. The aim of this work was to examine how high intensity ultrasound at a frequency of 24 kHz with an ultrasound probe of a nominal power of 400 W effects yeasts of Brettanomyces genus and sensory quality of wine. FTIR-wine analysis and detection of Brettanomyces yeast from wine samples have been done before and after ultrasound treatments. Ultrasound is efective in Brettanomyces destruction. Ultrasound has negative influence on wine flavour. Time, temperature and ultrasound sonde have strong influence on Brettanomyces and wine quality. Yeast isolates designated as 22A, A1, 3A and N4 metabolized substantial quantity of p-coumaric acid (70-80%) during 5 days of cultivation, and produced about 70 % of theoretical 4-ethyl phenol concentration with exception of N4 isolate (30 %). Yeast isolates 4B and N8 metabolized about 50 % of p-coumaric acid during 5 days of cultivation, and produced about 50 and 25 % of theoretical 4-ethyl phenol concentration respectively.