Characterization and differentiation of five "vinhos verdes" grape varieties on the basis of monoterpenic compounds

The aromatic profiles of three white grape varieties (Alvarinho, Loureiro, and Avesso) and two red varieties (Amaral and Vinhao) from the Vinhos Verdes region have been established with respect to the monoterpenic compounds, present either in free and in glycosidically bound fractions. Seventeen compounds have been identified and quantified in the free form and 21 in the glycosidically bound form. Loureiro variety is characterized by important levels of linalool in the free fraction, above the odour perception threshold; in contrast, Alvarinho and Avesso varieties do not contain compounds above the perception threshold. For Alvarinho, geraniol prevails, followed by linalool, while Avesso only has, in much low concentration, geraniol, nerol and citronellol; red varieties do not contain terpenic compounds. Loureiro and Alvarinho are still the richer varieties with regard to the glycosylated fraction; linalool and 3,7-dimethylocta-1,5-dien-3,7-diol have equivalent concentrations, and linalool is around the odour perception threshold; Avesso does not contain linalool. The isomers (Z) and (E) of 8-hydroxylinalool seem to differentiate white varieties; they are similar in Loureiro but the (Z) isomer prevails in Avesso and especially in Alvarinho; Avesso has a more balanced distribution. Amaral only contains alpha-terpineol, nevertheless of similar concentrator found in Loureiro; Vinhao has a more balanced distribution of isomers but the concentrations are very low. The results show that profiles of the terpenic compounds vary to a significant degree for the grape varieties studied and as is already known empirically, the white varieties are richer than red varieties, especially Loureiro. (C) 2003 Elsevier B.V. All rights reserved.