Proton Extrusion as Indicator of the Adaptive State of Yeast Starters for the Continuous Production of Sparkling Wines

Abstract

A rapid test to evaluate the adaptive state of active dry yeast (ADY) starters used in continuous sparkling wine production is proposed. This method is based on the determination of an exponential constant of ethanol-enhanced passive proton diffusion across the yeast plasma membrane, which can be estimated rapidly and easily. A correlation was found (correlation coefficient = 0.929) between the enhancement constant k and the specific death rate of yeast populations (harvested at different stages of starter preparation) cultivated in tirage conditions under 5.1 ± 0.1 x 10⁵ Pa CO₂ pressure. The results support the method validity and suggest the importance of an ADY adaptation prior to tirage inoculation.