Effect of grape temperature on the phenolic extraction and quality of Cap Classique made using whole bunch pressing
Van Jaarsveld, F P
Van Jaarsveld, F P
De Vries, F
Du Toit, W
Chidi, B S
Van der Rijst, M
Objectives & Rationale
The main objective of this study is to investigate the influence of grape temperature at harvest on phenolic extractability, composition, concentration and evolution during the different phases of sparkling winemaking, and quality, when whole bunch Chardonnay and Pinot Noir grapes are pressed in the making of Cap Classique.
Grapes from Vitis vinifera L. cv. Chardonnay and Pinot Noir grapes, from commercial cellars representative of a warm and a cool climatic region, respectively, were harvested (hand-picked) early morning at optimum maturity/ripeness at the sugar/acid ratio related to the production of Cap Classique, and transported and delivered to the Nietvoorbij cellar before 10h00. At the Nietvoorbij cellar grapes were divided into equal, representative lots, and chilled to 0, 10, 25 and 30˚C, respectively, representative of some individual practices and natural ranges. Freerun juice from lightly pressed whole-bunch grapes were inoculated with yeast IOC 18-2007, fermented and processed further. Blended base wines received tirage liqour, and underwent second alcoholic fermentation in the bottle. Wines were riddled, disgorged and crown capped. Samples were collected at various stages during the production of Cap Classique, analysed for total phenols and general wine parameters, and sensorially evaluated.
The temperature of grapes at pressing, achieved through overnight storage, has more of an impact on aroma of the Méthode Cap Classique wines than on the taste, and has an effect on the extraction of phenolics, but does not affect the oenological parameters. Sensory analysis of the wines made from grapes stored at 0 and 10ºC showed that the wines had generally more desirable aroma attributes such as fruity, fresh and floral compared to higher temperature treatments. Grapes stored at 25 and 30ºC produced wines which were associated with positive aroma attributes (i.e. buttery, caramel, oaky and nutty) most commonly associated with older sparkling wines, but they were plagued with negative aroma attributes such as VA, solvent-like and oxidation, which are not expected of only 9 month-old wines. Also, MCCs made from grapes stored at lower temperatures (0 and 10ºC) were found to have lower total phenolic content, colour intensity, and total hydroxycinnamates than wines made from grapes stored at higher temperatures (25 and 30ºC). This showed that there was greater phenolic extraction at higher temperatures. No changes in the phenolic content was observed throughout winemaking.
Grape temperature at the time of processing does impact MCC sensory and chemical quality. The greater extraction of phenolics at higher temperatures (25 and 30ºC) is not desired by TSW winemakers. Therefore, to ensure constant quality, MCC producers should preferably harvest grapes early morning and/or chill grapes before processing if such facilities are available. In cases where grapes are sourced in from different grape producers and regions, it would be ideal to obtain grapes that have been exposed to lower environmental at harvest, and transport temperatures.
Mafata, M, Buica, A, du Toit, W, Panzeri, V, van Jaarsveld, F P. 2018. The effect of grape temperature at pressing on the sensory perception of Méthode Cap Classique wines, South African Journal of Enology and Viticulture, v. 39 (1) https://doi.org/10.21548/39-1-2620
Mafata, M, Buica, A, du Toit, W, van Jaarsveld, F P. 2018. The Effect of Grape Temperature at Pressing on Phenolic Extraction and Evolution in Méthode Cap Classique Wines Throughout Winemaking, South African Journal of Enology and Viticulture, v. 39 (1) https://doi.org/10.21548/39-1-2621