engleski

Effect of Grapevine Solarization Technique on the Anthocyanin Content of Autochthonous

The main purpose of grapevine solarization technique is reflection of sunlight into the grapes, and therefore changes in light spectrum and temperature can be noticed. An artificial solarization experiment was conducted on a parcel of Teran grapevines grown in the subregion Istra (Brtonigla vineyard location) of Croatia in the year 2005 and 2006. Main organic acids (tartaric, malic, lactic, citric and succinic) were analysed by HPLC using DAD set at 210 nm on C-18 analytical column. Samples were prepared by solid phase extraction using SAX cartridges in order to clean up interferences like sugars and alcohols. It is well known that Teran is one of the red grape varieties characterized by high to very high total acidity (8, 0-14, 0 g/L) and high content of malic acid (4, 0-10, 0 g/L). Compared with standard vinestocks grown on bare soil, solarization technique also caused higher anthocyanins content in Teran wines, analysed by HPLC method just after the end of alcoholic fermentation. A simple and fast method was used for separation of nine anthocyanins in Teran wine by direct injection using DAD set at 518 nm. Phosphate buffer at pH 1.6 and acetonitrile were used as mobile phases. The low pH of the mobile phase is required to keep the anthocyanins homogeneous in the flavylium form according to the pH-dependent equilibria. The linearity was investigated for malvidine-3- glucoside in the range of 5-250 mg/L at seven concentration levels. All of the samples exhibited malvidin-3-monoglucoside as the major compound, representing about 55% of the sum of all individual anthocyanins. The strongest solarization effect was seen through the higher content of 3-O-glucosides of delphinidine, petunidin and malvidin and acetylated as well as coumarylated forms of malvidine and peonidin. Total phenolic contents of samples were also determined using the Folin-Ciocalteu method. The wines were sensory tested by the O.I.V./U.I.OE. method by 100 positive points. This study suggested that solarization technique positively influenced the quality of Teran wines.

wine; solarization; Teran; anthocyanins; HPLC

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