Volatile sulfur compounds (VSCs) and nonvolatile thiol-containing compounds (NVTCs), which are potential precursors of VSCs, were monitored by gas chromatography during fermentation of eight white grape musts: one Thompson Seedless, one Palomino, one Chenin blanc, two Sauvignon blancs, and three Chardonnays. The assimilable amino acid (EAA) concentration of the musts ranged from 480 mg/L to 2022 mg/L (mean = 1131 mg/L). Using a GC-flame photometric detector, three sulfur containing peaks were tentatively identified based on their retention times: hydrogen sulfide (H2S), ethylmercaptan, dimethylsulfide, and one unknown peak (RT, 9.7 min) was detected. The predominant VSC, H2S, was continuously produced throughout fermentation and was highest during rapid growth phase of yeast. All juices produced H2S most rapidly during rapid yeast growth, but musts with low EAA generally produced higher levels of H2S throughout the fermentation. Total H2S, which ranged from 112 to 516 mg/L, was inversely correlated with concentration of assimilable amino acids (p < 0.01) and with total nitrogen content (p < 0.10). H2S at the end of fermentation was negatively correlated with EAA (p < 0.01) and positively with days to dryness (p < 0.05). For all musts, concentration of NVTCs, primarily glutathione (GSH), steadily increased towards the end of fermentation. Final wine concentration of GSH (0.1 to 5.1 mg/L) was correlated with both total N (p < 0.01) and EAA (p < 0.05).
- Copyright 2000 by the American Society for Enology and Viticulture