DISTRIBUTION OF FREE AND GLYCOSIDICALLY BOUND MONOTERPENES IN THE SKIN AND MESOCARP OF MUSCAT OF ALEXANDRIA GRAPES DURING DEVELOPMENT

The major free and glycosidically bound monoterpenes of Muscat grapes accumulated during ripening. Approximately 90% of the monoterpenes were glycosidically bound, while only 10% were in the free odor-producing from in whole berries. The distribution of free and bound monoterpenes in the skins and mesocarp changed constantly during ripening of the berries. At harvest, 4.6% and 5.9% of the three major monoterpenes (linalool, geraniol, and nerol) occurred as free terpenes located in the skin and mesocarp, respectively, whereas 31% and 59% of total terpenes occurred as glycosides in the skin and mesocarp. Fluctuations in bound monoterpene concentrations during grape development seemed to correspond to changes in temperature. However, due to fairly low levels of free monoterpenes, the response of the free monoterpenes was less clearly related to temperature changes than that of the bound forms.