Tannin content and antioxidant capacity of five Greek red grape varieties

Tannins are located in skins and seeds and are responsible for important sensory and quality attributes of red grapes and wines, such as astringency, bitterness and colour stability. However, little is known regarding Greek Vitis vinifera varieties. The aim of this study is to evaluate the grape phenolic content and to present data that may contribute to the development of suitable winemaking techniques for these varieties. In this study berry attributes, skin and seed content of tannins and antioxidant capacity from five Greek Vitis vinifera varieties, namely 'Mavrotragano', 'Mandilaria', 'Kotsifali', 'Agiorgitiko' and 'Xinomavro' were analyzed. Significant differences were observed in berry weight and the distribution of berry component mass in mature berries, among the different varieties. 'Mandilaria' and 'Kotsifali' had the heavier berries while the higher contribution of skins and seeds in berry was observed in 'Agiorgitiko' and 'Mavrotragano' grapes respectively. According to the results, the higher content of seed tannins in berries was determined in 'Mandilaria' and the lower in 'Kotsifali'. Finally, varieties with high concentrations of tannins, 'Mandilaria' and 'Mavrotragano', also demonstrated significant high values of antioxidant capacity

Sensory and instrumental astringency determination in wine

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Differentiation of young red wines based on chemometrics of minor polyphenols constituents

For reasons of examining any possible discrimination of young red wines based on selected, minor polyphenols, a survey was carried out including 35 samples originating from three Hellenic native and three international Vitis vinifera cultivars from various regions of Greece. All samples were experimental wines vinified and stored under identical conditions, in an effort to minimize the effect of different winemaking technologies as well as aging. The polyphenols analyzed belonged to two categories: benzoic acid derivatives, including gallic acid, protocatechuic acid, vanillic acid, and syringic acid, and stilbenes, including astringin, piceid, and resveratrol (all trans isomers). Data handling employing discriminant analysis (DA) yielded very satisfactory categorization of samples in terms of both cultivar and geographical region of origin. This outcome was discussed with regard to the value of certain minor polyphenols that could serve as characteristic indices for discrimination of varietal red wines, after appropriate implementation of chemometrics. © 2007 American Chemical Society

The application of an improved method for trans-resveratrol to determine the origin of Greek red wines

A rapid and sensitive method has been developed for the determination of trans-resveratrol in wine. This method consists of a solid phase extraction step followed by a rapid HPLC quantification step (30 min). The improvement of this method consists of the washing step of the solid phase extraction method carried out at pH 8.0 (12% ethanol in a phosphate buffer solution), thus permitting a more efficient removal of the interfering phenolic compounds in conjunction with the required low volume of tested sample. Trans-resveratrol content was determined for 29 red Greek wines of appellation of origin. The concentrations found varied between 0.550 and 2.534 mg/l. The wines produced by grape varieties grown in the Greek islands (Rhodes, Crete and Paros) were richer in trans-resveratrol. The grape variety Mandilaria, in particular, was the Greek variety with the highest trans-resveratrol content. (C) 2001 Elsevier Science Ltd. All rights reserved