Abstract:

In this work, a spectrophotometric assay was used to investigate the lipoxygenase activity in Cabernet Sauvignon
grapes using linoleic acid sodium as a substrate as a function of reaction temperature, substrate concentration and pH. Gas
chromatography-mass spectrometry (GC-MS) was used to analyze the fatty acid composition in grape skin. The changes in
lipoxygenase activity and fatty acid composition in Cabernet Sauvignon during grape berry development were examined.
The enzyme had the highest activity under the reaction conditions: 40 ℃, a substrate concentration of 2×10-4 mol/L, and pH
7.0. The enzyme activity also showed good thermal stability at 80 ℃. At the veraison stage, the enzyme activity began to
increase, and reached the maximum level at 2 - 3 weeks before maturity followed by a sharp decrease and then stabilization
during the ripening stage. Thirteen kinds of fatty acids were detected in Cabernet Sauvignon grape skins. Palmitic acid and
stearic acid dominated the identified saturated fatty acids; the predominant unsaturated fatty acids were oleic acid, linoleic
acid and linolenic acid. The total fatty acid content reached the maximum at about 1 week before maturity.

Key words: Cabernet Sauvignon, lipoxygenase (LOX), fatty acid, enzyme activity, composition change