The effect of grape temperature on the phenolic extraction and sensory perception of Méthode Cap Classique wines

[摘要] ENGLISH ABSTRACT: The first sparkling wine in South Africa was released in 1971. The South African Cap ClassiqueProducers Association (CCPA), formed for the appreciation of Méthode Cap Classique (MCC)traditional style sparkling wines (TSW), was established in 1992 and has since contributed to thegrowth of these wines on a competitive footing with the international market. Generally, studies onTSW have focused primarily on the foam capability, volatile composition and autolytic character ofthe wines and very little on phenolic content of the wines. Phenolic compounds are important qualityindicators of wine. Their composition in wine is determined by various factors including grape variety,terroir, viticultural practice, and oenological practices. In this project, MCC wines were made by thetraditional method using Chardonnay and Pinot noir grapes harvested from two regions (Robertsonand Darling) and stored at 0, 10, 25 and 30ºC, over two vintages (2014 and 2015). The phenolicconcentration of the wine samples throughout the winemaking process was analysed byspectrophotometer and the aroma and taste of the final 9 month old sparkling wines performed. Thestudy was aimed at investigating the effect of the grape storage temperature on the phenolic contentand the sensory properties of MCCs through a quantitative phenolic analysis. The study found thatMCCs made from grapes stored at lower temperatures (0 and 10ºC) had lower total phenolic content,colour intensity and total hydroxycinnamates than wines made from grapes stored at highertemperatures (25 and 30ºC) showing that there was greater phenolic extraction from grapes storedat 25 and 30ºC. The total phenolics, as measured by spectrophotometer, was below the range citedin literature for Champagne made from the same cultivars. The sensory evaluation of the MCCscomprised a sorting analysis similar to that used for beers. Separating the aroma and taste sortingof the MCCs, the study showed a grouping of the MCCs according to temperature treatments forboth vintages. There were, however, clear vintage differences in terms of the attributes cited and thefrequency of citations. Based on frequency of citation, 2014 MCCs made from grapes stored at 0and 10°C were described by judges as being fruity, fresh and crisp whilst those made from grapes stored at 25 and 30°C were described as having oxidised fruit, volatile acidity and solvent-likearomas. The judges perceived less oxidation and VA (in terms of the frequency of citation) in thearoma of 2015 MCCs, although higher temperature treatments were still associated with lessdesirable attributes compared to lower temperature treatments. Judges were better able to separatethe Darling wines according to treatments compared to the Robertson wines. This study has shownthat the grape storage temperature has an effect on the phenolic extraction and the sensoryperception of MCCs aged 9-months with no changes in the phenolic content observed throughoutwinemaking.

[发布机构] Stellenbosch University