Light lees that spent more than one year in barrels were used for ultrasound-assisted yeast lysis (22 W/L, 18 °C) in a model wine. For comparison, a classical yeast autolysis at mild temperature (25 °C) was performed.
The effect of ultrasound on lees was evaluated by analysing the release of proteins and polysaccharides to the model wine, and the viability of the yeasts contained in the lees.
Under conditions tested, ultrasound-assisted yeast lysis increased the concentrations of proteins and polysaccharides in the model wine due to the release of these compounds from yeasts.
Unlike the classical autolysis, ultrasound led to a high cell disruption, and after 20 h of ultrasonic treatment, viable cells were hardly found.
Furthermore, the final cell concentration for the ultrasound-assisted yeast lysis was much lower than that for the classical autolysis. The inactivation rate constant of ultrasound-assisted yeast lysis was 2.54 × 10−5 s−1.
Finally, the morphological changes in cells were examined by scanning electron microscopy to verify the effect of ultrasound on yeast cells.