Yeast hulls: effect on spontaneous fermentation in different vinification conditions

Abstract

The effect of the addition of yeast hulls in vinification was investigated during three consecutive years. The study was carried out in the experimental winery of C.I.D.A in La Rioja (Spain) with free running white grape juice of the Viura variety. Four different vinifications were studied. In two of these vinifications, stuck fermentations were detected. In all the studies, the addition of yeast hulls (yeast ghosts) improved the fermentation kinetics, increasing the number of viable yeasts at the end of the exponential stage and decreasing the final content of reducing sugars. This work revealed a new effect of yeast hull addition which had not been identified previously; their selection effect on the wild yeast strain in spontaneous fermentation.