Chemical Changes of Some Important Sulfur-Containing Compounds
We added glutathione (300 mg/L) to a Chardonnay juice prior to yeast inoculation. .After primary fermentation the wine was subjected to malolactic fermentation. The resulting wines were compared to corresponding control wines which were made in parallel without glutathione addition. Results indicate that added glutathione does not seem to contribute to sulfur defects that occur in wines. Indeed, if anything, glutathione seems to provide some protection against oxidation in the resulting wines. We added glutathione (300 mg/L) to a Cabernet Sauvignon must just after crushing. The must was fermented to dryness and subjected to malolactic fermentation. The resulting wine was compared to the corresponding control wine which was made in parallel without glutathione addition. Testing shows some interesting differences, but once again no sulfur defects were found in the wine to which glutathione had been added. Unexpectedly, the differences noted in testing are related to color and tannin. We determined the amount of tannin in the Cabernet Sauvignon wines using a plate binding assay we developed in conjunction with another project. We found that the amount of tannin in the wine to which glutathione was added was significantly higher than the control wine. There also appears to be more anthocyanin in the wine to which glutathione was added. The results related to anthocyanin and tannin were completely unanticipated, but the experiments are consistent with the white fermentations in showing that glutathione added to a must prior to yeast inoculation does not give rise to sulfur defects in the resulting wine. We have compared several parameters related to color in the Cabernet Sauvignon wines made with and without added glutathione. Total red color was higher in the glutathione treated wine at pH 3.6 even though the percent color due to anthocyanins was lower than in the control. The percent of the color due to polymer was higher in control wines than in the glutathione-treated wine, and total phenols and tannin were higher in glutathione-treated wine. The largest difference was observed in the amount of color due to copigment complex. Color due to copigmentation as only 2%for the control wine but was found to be 23%in the glutathione treated wine, a difference of more than 10 fold.