Sugar concentration is a major physical property analyzed in grapes and wine. The amount of sugar available will determine the sweetness of wine flavor. Residual sugar is also important to know as any sugar present in wine is a potential substrate for microbial growth. Sugar concentrations are commonly analyzed by measuring the density of juice or wine. Brix is the unit of measurement used in the United States when analyzing density. One degree of Brix is roughly equivalent to 1% sugar in solution or 10 g/L of sugar. Density measurement is normally done with a hydrometer.
Sugar concentrations in ripe grapes will range in Brix values from the low to upper twenties. Full physiological ripeness in grapes is about 25 Brix. Values higher than that come from dehydration of the berries as they begin to raisin. Residual sugar levels below 0.4 Brix, or 4 g/L sugar are considered complete fermentations.
