Volatile Aroma Constituents of Vitis Rotundifolia Grapes

¹ Departments of Chemistry and of Viticulture and Enology, University of California, Davis

1. The volatile essence compounds from mixed varieties of Vitis rotundifolia have been determined to include ethyl alcohol, n-butyl alcohol, n-hexyl alcohol, -phenylethyl alcohol, an acetate ester, a laurate ester, and an isopropyl ester. Methyl alcohol, n-hexanal, 2-hexenal, and acetal also are probably present.

2. The volatilte essence from the crop of a later year from the same vines was isolated by a technique which included the aroma material produced by fermentation of the grapes. This essence was found to contain methyl alcohol, isoamyl alcohol, acetaldehyde, biacetyl, n-hexanal, 2-hexenal, isobutyraldehyde, ethyl acetate, a caproate ester, a caprylate ester, and a caprate ester in addition to the compounds found definitely present in the unfermented essence. Methyl-ethyl ketone and acetal were also probably present.

3. A reduced pressure pot distilling volatile essence isolation technique is compared with a flash evaporation technique and it is demonstrated that the latter technique isolates an essence which is probably most nearly representative of that which actually exists in the intact grape.

4. Vitis rotundifolia volatile essence is shown to be free of nitrogen and sulfur containing compounds, thus providing a possible means of differentiation from labrusca varieties which contain anthranilic acid esters.

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