Changes of free and glycosidically bound monoterpenes and aromatic alcohols in Moscatuel and Ruby Seedless table grapes during development
Aims: The evolution of free and bound aromatic compounds (monoterpenes and aromatic alcohols) during ripening was determined in two cultivars of Vitis vinifera : Moscatuel (muscat aroma) and Ruby Seedless (neutral aroma). The aim was to identify the aromatic compounds in both varieties and to understand the differences in their aromatic characteristics.
Methods and results: The aromatic compounds were measured at six different maturity stages by gas chromatography and mass spectrometry. The most abundant compounds detected in Moscatuel grapes were linalool, geraniol, citronellol, nerol, citral, α-terpineol, linalool oxide I, linalool oxide II, rose oxides, benzyl alcohol and 2-phenylethanol. In general, the concentration of the main terpene compounds increased during grape development. The most abundant compounds detected in Ruby Seedless grapes were benzyl alcohol and 2-phenylethanol at concentrations higher than those observed in Moscatuel. The concentrations of the bound compounds were higher than those of the free forms, except for geraniol, nerol and citronellol in Ruby Seedless. Based on the Odour Activity Values (OAVs), linalool was the most odour-active odorant at the end of maturation in Moscatuel grapes. Other monoterpenes potentially contributing to the muscat aroma (OAV > 1) of this variety were rose oxide, citral and geraniol. In Ruby Seedless none of the studied compounds showed OAV > 1.
Conclusion: Several differences between Moscatuel and Ruby Seedless were observed in the monoterpene and alcohol profile and their contribution to the aroma.
Significance and impact of the study: This study characterizes and compares two non-previously described varieties of table grape, very appreciated by consumers, with different aromatic characteristics.
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