Considerations of the Biological Significance of Some Volatile Constituents of Grape (Vitis spp)

Abstract

The intensity and diversity of volatile constituents in the fruit of grape (Vitis spp.) cultivars assume importance to humans as sources of aroma and flavour of wine. These volatile constituents include hydrocarbons, esters, aldehydes, ketones, alcohols and compounds of miscellaneous structure (Schreier 1979). Their determination has been based invariably on juice expressed by maceration of the fruit or its parts and usually by chromatographic analysis of headspace or solvent extracts. Many of these constituents are common to most cultivars, and many are probably the products of hydrolytic andlor oxidative reactions resulting from the disruption of the internal compartmentation of the plant cells. For example, six carbon aldehydes form readily from unsaturated fatty acids under such conditions (Schreier 1979). While some of the volatile constituents of grape juice can therefore be considered products of cellular disorganisation, others are clearly products under genetic control, particularly those compounds associated with specific cultivars. In other biotic systems compounds of this latter group are now known to have important functions not associated directly with primary metabolism and have thus become known as secondary metabolites. Their adaptive value seems to rest with a role in ecological interactions with other plants, animals andlor the physical environment.