Winetech Technical Yearbook 2022

AUGUST

Cork or crown closures during bottle fermentation of MCC? THE ARC AND THE CAP CLASSIQUE PRODUCERS ASSOCIATION UNDERTOOK A COLLABORATIVE PROJECT TO INVESTIGATE A SELECTION OF BOTTLE-FERMENTED SPARKLING WINES CLOSED WITH CORKS AND CROWN CAPS.

LISA LOTTERING

BY NEIL JOLLY

INTRODUCTION The use of crown caps during the production of bottle-fermented sparkling wine is a standard practice worldwide. Before the development of crown caps, bottles were closed with a cork held in place with a metal staple (agrafe). The first crown caps were used commercially in the 1960s. 1 In South Africa, there are an estimated 250 producers of bottle-fermented sparkling wine (Méthode Cap Classique or MCC). 2 In an ever-more competitive market, one of the tools that can be used to produce niche products is the use of a cork instead of a crown cap during the second fermentation. Some international producers still follow this practice for the production of their premium products despite the risk of cork taint. For example, the Champagne Dom Perignon Plénitude can be in contact with a cork while on the yeast lees for up to 15 years before being released. 3 Anecdotal observations made by some MCC producers are that the use of a cork leads to stylistic changes in the wines, such as smaller bubbles and an increase in wine complexity. It has also been observed that this beneficial ‘cork effect’ becomes more noticeable the longer the wine on the lees is in contact with the cork. In still wines it has been shown that compounds such as phenolics migrate from the cork to the wine at the cork-wine interface, 4,5,6 but not much is known about sparkling wine where a two-disc cork is used. This article is a summary of information found in a publication in the South African Journal of Enology and Viticulture , Volume 42. 7 MATERIALS AND METHODS Six treatment pairs of commercially prepared bottle-fermented sparkling wines were obtained for analyses from three South African producers (2012, 2013, 2015 and 2018 vintages). These wines had been in contact with the yeast lees between four and 72 months. For each sparkling wine pair, the only differences between the wines were a cork or crown cap closure during fermentation and maturation on lees. Wines used for chemical analyses had their lees intact, while wines for sensory analyses

investigations were clarified by disgorging. The disgorged wines received no dosage. Individual bottles served as replicates and the results were analysed statistically to ensure validity of the data. RESULTS AND DISCUSSIONS In this study each cork-crown wine pair originated from the same bottling tank with the only variable being a cork or crown cap closure for the second fermentation and ageing on lees. Conse quently, individual cork-crown wine pairs could be compared and overall trends deduced across the various wine pairs. A variation in bottle pressure within treatment replicates was observed, but overall, crown-capped wines tended to have higher pressures than their cork-closed counterparts. The crown cap was therefore deemed a more effective barrier than the cork for maintaining bottle pressure. Notwithstanding, the final pressure of the cork-closed wines was well above the legal minimum limit (>300 kPa) for the final products. Analyses of infra-red spectral fingerprints generated by an Alpha spectrophotometer during standard wine analyses showed varying degrees of separation between the cork-closed and crown-capped wines for the oldest vintages, and less/none for the youngest vin tages (as illustrated in figure 1a and 1b). This indicates a chemical difference in the wine matrix of the older wines and supports the MCC producer’s observations that longer periods of cork contact are required before a ‘cork effect’ is noticeable. Further chemical analyses showed that total acidity, pH and malic acid content, largely determined during base wine prepa ration before bottling, were not affected by the closure and were the same for each cork-crown wine pair. Yeast autolysis, generally regarded as a positive contributor to the sensory profile of bot tle-fermented sparkling wines, also leads to an increase in mouth feel (body) of wine and an increase in nitrogen levels. Therefore, YAN (yeast assimilable nitrogen) and total extract measurements can serve as broad indicators of the progress of autolysis. In the youngest wine (2018 vintage), which had only been on the lees for four months, it appeared that autolysis had started sooner in the

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WINETECH TECHNICAL YEARBOOK 2022