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Wurth K.,Fachgebiet Weinanalytik und Getrankeforschung | Bonerz D.,Fachgebiet Weinanalytik und Getrankeforschung | Will F.,Fachgebiet Weinanalytik und Getrankeforschung | Patz C.-D.,Fachgebiet Weinanalytik und Getrankeforschung | And 4 more authors.
Deutsche Lebensmittel-Rundschau | Year: 2012

Genuine grape juices were produced by means of usual juice technology from the grape varieties Pinot noir, Rotberger, and Dunkelfelder in the vintages 2003, 2004, and 2005. The primary goal was the investigation of anthocyanin losses and the effect on the colour after storage of the samples at 4, 20, and 37°C over 12 months. Negative colour alterations occurred rather early especially at 20 and 37°C. On the basis of the spectral data (400-700 nm) a fast reduction of the colour intensity at 520 nm was evident. The CIELAB colour determination failed to work with the L*-value (lightness) of the colour-intensive Dunkelfelder juice. Generally, the L*- values increased during storage, and the juices lightened. The red-green moieties (a*) decreased, whereas the blue-yellow moieties (b*) were shifted to blue. Visually, these shifts resulted in a reduction of the red colour. Total polyphenols and the antioxidant capacities showed vintage differences up to 100% within a wide range of 403 mg/L (Rotberger 2004) to 4760 mg/L (Dunkelfelder 2005). Significant polyphenol losses with analogous effects on the antioxidant capacity occurred only at the 37°C storage. All varieties contained 3-O-glucosides of delphinidin, cyanidin, petunidin, peonidin, and malvidin, cv. Dunkelfelder additionateiy acetyiated and coumaroylated types. Regarding the anthocyanin concentrations, we also found strong vintage dependencies up to 100%. In comparison to cv. Dunkelfelder (1115-2275 mg/L), cv. Pinot noir and Rotberger turned out to be anthocyanin- poor varieties, which already at 4°C showed anthocyanin losses of > 50 % in one year. Source

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