## 2 Results and Discussion
### Quantification of Polyfunctional Thiols in Commercial Wines
For example, wine grapes are typically hand-harvested in the Finger Lakes and Napa, and it is reported that hand harvesting grapes results in lower 3-MH precursor concentrations and eventually lower 3-MH in wines as compared to machine harvesting [28]. However, this argument would not be appropriate for California Central Coast where machine harvesting is common. Other factors reported to affect final 3-MH concentrations include vineyard nitrogen availability, yeast assimilable nitrogen, abiotic stresses, disease pressure, oxygen status during maceration, and post-fermentation oxidation [1], and a recent study has reported modest correlations of over 20 grape metabolites (amino acids, fatty acids, _etc._) with wine 3-MH concentrations [29]. Discerning which of these factors would lead to low 3-MH concentrations in Sauvignon blanc and Gewurztraminer samples in this study is not possible. It was found that 3-MHA was only detectable in two out of the 30 New York wines evaluated; one rose wine, and one Sauvignon Blanc wine. Formed by partial enzymatic acetylation of 3-MH during fermentation [30], 3-MHA will decrease during storage due to acid-catalyzed hydrolysis [31]. As a result, average 3-MHA values are reported to be 10%-20% the concentration of average 3-MH values in Sauvignon blanc [29], and can be much lower [24]. Since the average 3-MH concentration across New York State wines in this study was 195 to 569 ng/L, and many of the wines were 2-3 years old at the time of analysis, it is unsurprising that 3-MHA was generally below the 17 ng/L detection limit of the method. Additionally, New York State grapes tend to be low in \(\alpha\)-amino acids as compared to other regions [32], and several of these amino acids have been correlated with lower 3-MHA/3-MH ratios [29]. Furthermore, 3-MHA could not be quantified in the California Sauvignon blanc samples due to an unknown interference on the quantifier ion, which could not be identified by library search. However, 3-MHA could be detected in California Cabernet Sauvignon, and mean values across sub-regions (46-67 ng/L) were approximately 10% of 3-MH concentrations. Similar to 3-MH, there is a lack of analytical data regarding 3-MHA in red wines, but values are within the range estimated for Bordeaux red wines, 1-200 ng/L [27]. In contrast to 3-MH and 3-MHA, mean 4-MMP concentrations in both New York (27 ng/L) and California (44-50 ng/L) Sauvignon blanc wines were greater than the mean values (5-10 ng/L) reported for Sauvignon blanc from most other wine regions [24]. The highest reported mean value for 4-MMP in this previous survey was for the Wairarapa region of New Zealand (19 ng/L), but this region also had order of magnitude higher concentrations of 3-MH. In addition, 4-MMP was not detectable in other _V. vinifera_ wines, except for trace concentrations (mean = 2.5 ng/L) in NY State Riesling wines. To our knowledge, this is the first report of thiol concentrations in any American wines from specific wine regions, rather than the general category of US wine [24]. The study also included the first analysis of thiols in wines produced from interspecific hybrids-Niagara and Cayuga White. The former contains _V. labrusca_ parentage, and the latter is a complex interspecific hybrid with mixed parentage. The 3-MH concentrations in Cayuga White were significantly lower than in _vinifera_ wines, and the other two thiols were not detectable. However, concentrations of 4-MMP in New York Niagara (mean = 18 ng/L) did not differ significantly from New York Sauvignon blanc (\(p>0.05\)), and were significantly higher than all other varietal wines (\(p<0.05\)). The \"foxy\" smelling \(o\)-aminoacetophenone and methyl anthranilate have previously been implicated in contributing to Niagara juice and wines [33,34]. Because 4-MMP exceeded sensory threshold by an order of magnitude in the majority of Niagara wines, 4-MMP may also be important to the varietal character of Niagara wines, but confirmation by sensory studies was not part of this study.