Monoterpenic Characterization of White Cultivars from Vinhos Verdes Appellation of Origin (North Portugal)

The monoterpenic composition of Alvarinho, Arinto, Avesso, Azal, Bawtoca, Loureiro and Trajadura Vitis vinifera cultivars from the Vinhos Verdes region (Portugal), in respect to free volatile compounds as well as glycosidically bound aroma precursors, was determined by GC-MS after adsorption on XAD-2 resin. Eighteen monoterpenic compounds were identified and quantified in the free form and twenty-two compounds in the glycosidically bound form. In the free fraction, the Loureiro variety could be easily differentiated from the other six varieties by the important levels of linalool, above the odor perception threshold. This was in contrast to Alvarinho, Avesso, Arinto, Azal and Trajadura, where geraniol prevailed. The Batoca variety showed a very poor monoterpcnic profile in the free form. On the other hand, Alvarinho was the richest variety in respect to the glycosidically bound form, followed by Loureiro. In this fraction, linalool and 3,7-dimethylocta-1,5-dien-3,7-diol were the most abundant compounds in the Loureiro grape cultivar; additionally, the isomer (E)-8-hydroxylinalool was in a higher concentration than (Z)-8-hydroxylinalool (sub-region Of Sousa), while for the rest of the varieties the (Z) isomer prevailed.