The Glucose-Fructose Ratio of Vitis Vinifera Grapes

Abstract

Concentrations of glucose, fructose, and total soluble solids in the fruits of 28 table varieties, 26 red wine varieties, and 24 white wine varieties of Vitis vinifera L. were determined at an early and a late stage of maturity. All fruits were from virus-free vines grown at Davis, California. The glucose-fructose ratio of table varieties ranged from 0.74 to 0.97 (mean 0.91 for the slightly to moderately ripe fruits, and 0.83 for the very ripe to overripe fruits). The ratio for the wine varieties ranged from 0.74 to 1.05 (mean 0.94 for the early-harvested fruits, and 0.85 for the late-harvested fruits). In every variety there was either a decrease or no change in the glucose-fructose ratio between the early- and the late-harvested fruits.

Table varieties with relatively high amounts of fructose (glucose-fructose ratio less than 0.9) included Beauty Seedless, Black Corinth, Canner, Early Muscat, July Muscat, Loose Perlette, Niagara, Perlette and Black Monukka. High-fructose wine varieties were Chardonnay, Chasselas doré, Feher Szagos, Green Hungarian, Pinot blanc, Pinot gris and Red Veltliner.

Varieties that were relatively high in glucose (glucose-fructose ratio greater than 0.9) at the late stage of fruit maturity were Exotic, Malaga, and Muscat of Alexandria table varieties, and Burger, Chenin blanc, Early Burgundy, Emerald Riesling, Flora, Grey Riesling, La Rienha and Zinfandel wine varieties.

The glucose-fructose ratios of mature fruits from six varieties were lower during the warm 1966 season than during the cooler 1964 and 1965 seasons.