Biochemical aspects of the lipids in Vitis vinifera grapes (Macabeo variety). Part 1. Linoleic and linolenic acids as aromatic precursors

The aim of this work has been to study the temporal evolution during the vegetative stages of the composition of linoleic and linolenic acids, lipoxygenase activity and C 6 aldehyde content in Macabeo grapes. Linoleic acid was found to be the main fatty acid, especially in skin and pips, and higher levels of linolenic acid have been found in the polar lipid fraction, and in the pulp. Lipoxygenase activity is higher during the semi‐ripe stage, and the aldehydes are not direct products of lipoxygenase action. There appears to be no direct relationship between the contents of linoleic and linolenic acids, lipoxygenase activity and C 6 aldehydes in Macabeo grapes during their vegetative stages. All these results suggest that in addition to lipoxygenase other enzyme systems must be involved in the metabolic processing of unsaturated fatty acids to C 6 aldehydes.