Effect of grape temperature on the phenolic extraction and quality of Cap Classique made using whole bunch pressing

Project Number
WW 08-36

Project title
Effect of grape temperature on the phenolic extraction and quality of Cap Classique made using whole bunch pressing

Project leader
Van Jaarsveld, F P

Team members
Van Jaarsveld, F P
De Vries, F
Du Toit, W
Versari, A
Chidi, B S
Paulsen, C
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.

Methods
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.

Key Results
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.

Conclusion/Discussion
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.

Articles
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

 

  – Record end –

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