RT Journal Article
SR Electronic
T1 Levels of Glutathione and Activities of Related Enzymes During Ripening of Koshu and Cabernet Sauvignon Grapes and During Winemaking
JF American Journal of Enology and Viticulture
JO Am J Enol Vitic.
FD American Society for Enology and Viticulture
SP 264
OP 270
DO 10.5344/ajev.1999.50.3.264
VO 50
IS 3
A1 Tohru Okuda
A1 Koki Yokotsuka
YR 1999
UL http://www.ajevonline.org/content/50/3/264.abstract
AB The glutathione content of berries and wines and the activities of six enzymes related to glutathione metabolism were investigated during the ripening of Koshu and Cabernet Sauvignon grapes and during winemaking from the two varieties. In general, changes associated with ripening were similar in both. The glutathione content in berries increased during ripening, and over 90% of it was reduced. The highest levels of reduced glutathione were 107 and 69 nmol/g fresh weight of Koshu and Cabernet Sauvignon grapes, respectively. Catalase, nonspecific peroxidase, and ascorbate peroxidase activities were undetectable in grapes of either cultivar during ripening, but glutathione reductase, dehydroascorbate reductase, and glutathione peroxidase activities were detected in both. Dehydroascorbate reductase showed a high level of activity (0.03 U/g fresh weight) during berry ripening, but the activity rapidly disappeared at 18° to 19° Brix. The levels of glutathione reductase and glutathione peroxidase were low or absent until 18° to 19° Brix, after which they increased. These enzyme activities may indicate maturity of the grape berry. During winemaking, the activities of glutathione peroxidase and dehydroascorbate reductase decreased but glutathione reductase showed increased activity in both wines, which was probably derived from yeast.