Influence of culture and nutritional conditions on self-flocculation of a Kloeckera apiculata wine strain

Abstract

The current work examines the environmental conditions to control the expression of self-flocculation of Kloeckera apiculata mc1 isolated from Argentinian grapes with proven beneficial effect on wine aroma. Temperature had a direct effect on the expression of flocculation resulting in an increase in the number of zymolectin sites determined with a BSA-Gal-FITC probe and quantified with the Scatchard plot. Agitation had a positive effect on yeast flocculation and the effect did not correlate with an increase in the hydrophobic index. The addition of glucose, fructose or ethanol to yeast nitrogen base medium without amino acids or ammonium sulphate stimulated flocculation. Assimilative nitrogen sources had a negative impact on flocculation in the absence of an energy source. During winemaking, control of flocculation by environmental factors such as temperature and the presence of nutrients could be applied in order to optimize the fermentation process and hence the quality of the final product. Knowledge of the effect of different parameters on flocculation of the wine yeast K. apiculata mc1 allows prediction of the behaviour of this yeast during fermentation.