Winetech Technical Yearbook 2022

mass loss kinetics measurements been taken on different bottles. However, the ge trend across all treatments showed that the cork wines retained their CO 2 nt marginally better than the crown-capped wines after pouring.

had, on average, similar bubble counts. Individually, two wines had notable higher bubble counts after 10 and 20 minutes for the cork-closed wine, compared to their crown-capped counterpart wine. The remaining wine pairs either showed conversely more bubbles in the crown-capped wine or no differences between the two closure types. A tentative conclusion can therefore be made that the closure type does affect the number of bubbles visible in the glass and, in some instances, a cork-closure was more amenable to retaining the appearance of bubbles in a glass of wine for the first 10 minutes after pouring. The CO 2 content of a sparkling wine has been proposed to affect the aroma. Droplets originating frombursting bubbles at the surface of the wine can release aromatic compounds into the immediate atmosphere in the glass. 5,6 This would have a direct effect on how a judge or consumer perceives the wine. The higher the concentration of dissolved CO 2 in the wine, the faster the bubble formation, the larger the bubble size and higher the number of bubbles that can be released from the wine (effervescence). 6 Therefore, the release of aroma compounds out of the glass will also be faster and could be lost to the atmosphere. In this study, the cork wines tended to have lower pressure and dissolved CO 2 than the crown-capped wines, which based on the aforementioned discussion, should lead to slower bubble formation, smaller bubble size and slower release of bubbles and aroma components from the wine glass. This would increase the perceived aroma in the glass. These observations also correlate with the higher number of bubbles counted. The differences in wine pressure could therefore be one of the underlying reasons why the MCC producers observe that cork-closed wines have better foam stability and bubble retention time than crown-capped wines. CONCLUSIONS Six pairs of wines from five vintages, closed by either a cork or crown cap, were investigated. An effect on the CO 2 kinetics was observed after the wines were poured. Cork-closed wines lost CO 2 slower than the crown-capped wines and had visually more bubbles. Based on the data generated in this study, anecdotal observations by MCC producers on the effect of cork on foam stability and bubble texture are tentatively supported. ABSTRACT Carbon dioxide (CO 2 ) content is essential for the bubbles in sparkling wine. Anecdotal evidence suggests that CO 2 kinetics (behaviour of the bubbles) in the wine glass can be affected if a cork closure is used during production instead of the customary crown cap. In a collaborative project undertaken by the ARC and the Cap Classique Producers’ Association, six pairs of MCC wines, closed by either a cork or crown cap during production, were investigated. It was found that the cork-closed wines tended to lose CO 2 slower from the glass after being poured than their crown-capped counterparts. Bubble counts in the cork closed wines were higher than the crown-capped wines for the first 10 minutes after pouring. The data generated tentatively supports the anecdotal evidence that cork usage during the second fermentation and maturation on the yeast lees has a positive effect on the CO 2 kinetics. ACKNOWLEDGEMENTS Le Lude Cap Classique, Graham Beck Wines and Anthonij Rupert Wyne for donating wines and the Cap Classique Producers’ Association for initiating this investigation. ARC Infruitec Nietvoorbij and Winetech for funding. Pieter Ferreira and Paul Gerber for assistance and technical expertise. Prof Gerard Liger-Belair and Dr Clara Cilindre, University of Reims, Reims, France, for sharing their expertise and protocols. Denis Bunner, Champagne Bollinger, for sharing his expertise on Champagne. REFERENCES https://www.wineland.co.za/effect-of-cork-or-crown-cap closures-on-mcc/

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FIGURE 1. Total CO 2 mass loss from an ISO standard tasting glass of six pairs of Méthode Cap Classique sparkling wine after 20 minutes ± stan dard deviation. Comparison of a wine fermented under cork (orange) and crown cap (blue). Within a cork and crown wine pair, bars with the same letter do not differ significantly (p<0.05). The second part of the CO 2 kinetic evaluation determined bubble counts in four of the six sets of wine using photographic images of glasses of wine. The initial average count (time zero) over all treatments varied greatly, but was slightly higher for the cork-closed wine (881 ± 488 bubbles/image) than the crown capped wine (826 ± 197 bubbles/image). The use of a single flute glass for all the measurements eliminated bubble nucleation sites as a variable, therefore, the observed differences can be ascribed to intrinsic wine characteristics. The number of bubbles counted per individual glass decreased exponentially over 20 minutes, which was similar to the trend observed for mass loss. Expressing the bubble count as a percentage of the number initially present in the glass, showed that after 10 minutes in the glass, cork-closed wines generally had higher bubble counts than crown-capped wines (figure 2). However, this was not sustained and after 20 minutes, the cork-closed and crown-capped wines GURE 1. Total CO 2 mass loss from an ISO standard tasting glass of six pairs of Méthode Cap Classique sparkling wine after 20 minutes ± standard deviation. mparison of a wine fermented under cork (orange) and crown cap (blue). Within a and crown wine pair, bars with the same letter do not differ significantly (p<0.05). econd part of the CO 2 kinetic evaluation determined bubble counts in four of the ts of wine using photographic images of glasses of wine. The initial average count zero) over all treatments varied greatly, but was slightly higher for the cork-closed (881 ± 488 bubbles/image) than the crown-capped wine (826 ± 197 es/image). The use of a single flute glass for all the measurements eliminated e nucleation sites as a variable, therefore, the observed differences can be bed to intrinsic wine characteristics. The number of bubbles counted per individual decreased exponentially over 20 minutes, which was similar to the trend observed ass loss. Expressing the bubble count as a percentage of the number initially nt in the glass, showed that after 10 minutes in the glass, cork-closed wines ally had higher bubble counts than crown-capped wines (Figure 2). However, this not sustained and after 20 minutes, the cork-closed and crown-capped wines had, erage, similar bubble counts. Individually, two wines had notable higher bubble s after 10 and 20 minutes for the cork-closed wine, compared to their crown ed counterpart wine. The remaining wine pairs either showed conversely more es in the crown-capped wine or no differences between the two closure types. A ative conclusion can therefore be made that the closure type does affect the number ubbles visible in the glass and, in some instances, a cork-closure was more nable to retaining the appearance of bubbles in a glass of wine for the first 10 tes after pouring. ative conclusion can therefore be made that the closure type does affect the number ubbles visible i the glass and, in som instances, a cork-closur was mor nabl to retaining the ppearance f bubbles in a glass of wine f r the first 10 tes af er pourin .

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58 (b) GURE 2. Percentage remaining bubbles in a flute glass of Méthode Cap Classique ne from four pairs of cork-closed (blue) and crown-capped (orange) bottles (a) 10 nutes, and (b) 20 minutes after pouring. The bubble count was derived from three b-sample photographic images of a flute wine glass poured from a single bottle of wine. (b) GURE 2. Percentage remaining bubbles in a flute glass of Méthode Cap Classique ne from fou pairs of cork-closed (blu ) a d crown-capped (orange) bottles (a) 10 utes, and (b) 20 minutes after pouring. The bubble count was derived from three b-sample photographic im g s of a flute wine glass p red from a single bottle of wine. CO 2 content of a sparkling wine has been proposed to affect the aroma. Droplets nating from bursting bubbles at t e urface of the wine can release aromatic FIGURE 2. Percentage remaining ubbles in a flute glass of Méthode Cap Classique wine from four pairs of cork-closed (blue) and crown capped (orange) bott e (a) 10 minutes, and (b) 20 minutes fter pour i g. The bubble count was erived from th ee sub-sample photog aphic images f a flute wine glass poured from a sing e b ttl of wine. WINETECH TECHNICAL YEARBOOK 2022 CO 2 content of a sparkling wine has been proposed to affect the aroma. Droplets

For more information, contact Neil Jolly at jollyn@arc.agric.za.