CHANGES IN CONCENTRATION OF NITROGENOUS COMPOUNDS DURING FERMENTATIONOF WHITE GRAPE MUSTS AT PILOT-PLANT SCALE

Five vinifications were performed in 500 L tanks using two musts of th e Malvar white grape variety. Four vinifications were carried out with or without the addition of sulphur dioxide by spontaneous fermentatio n and by a mixed culture of yeasts (Kloeckera apiculata, Torulaspora d elbrueckii and Saccharomyces cerevisiae var ellipsoideus). A fifth exp eriment was performed with the addition of sulphur dioxide and the ino culation of a commercial active dry yeast (Saccharomyces cerevisiae 71 B). The decrease in amino acids during fermentation was similar in all the experiments carried out on the same must in which there was no ma lolactic fermentation, regardless of the species of yeast conducting t he fermentation, the free amino acid content of the corresponding must or whether sulphur dioxide was added to the musts or not. There was a smaller decrease in free amino acid concentration in wines where malo lactic fermentation took place. This could be related to the release o f amino acids from the wines' peptides by the peptidase activity of la ctic acid bacteria.