Green odorants of grape cluster stem and their ability to cause a wine stemmy flavor.

Five aliphatic carbonyl compounds and two methoxypyrazines (MPs) were identified as olfactory dominant green odorants in macerated grape cluster stems of Vitis vinifera var. Cabernet Sauvignon and Chardonnay by a gas chromatography eluate sniffing and dilution analysis technique. Quantitative analysis of these odorants and related volatiles showed that the MP content of the stems was higher than those of the berry or leaf samples, though the aliphatic carbonyl compound content of the stems was not as high as the other parts. The addition of blended stems to the vinification process increased the MP content of the wine, but the identified aliphatic green odorants of the macerated stems were not detected in the wine. Keywords: Grape stem odorant; Cabernet Sauvignon; Chardonnay; methoxypyrazine; stemmy flavor; Vitis vinifera; wine