Changes in the composition of ripening grapes in a warm climate

Abstract

Grapes from 15 wine varieties of Vitis vinifera selected for suitability in warm areas were sampled over their ripening period in 1971 and 1972. Samples were analysed for total soluble solids, titratable acidity, pH, tartrate and malate. At maturity, titratable acidities ranged from 7.3 to 14.0 g l-1and pH from 2.8 to 3.6. In every instance pH was lower in 1971 than in 1972, but there was no pattern evident for titratable acidities. At the commencement of ripening the concentration of malate was always higher than of tartrate, and the rate of decrease of malate was faster than of tartrate. In the final stages of maturity acid losses of up to 1 g l-1 every ten days were common. Based on tartrate : malate ratios, the following varieties warrant further investigation: Barbera, Cabernet Sauvignon, Emerald Riesling, Gewurztraminer, Merlot, Petite Sirah, Pinot Noir, Semillon and White Riesling.