Ask the AWRI - Carbonic Maceration

ask the Ask the AWRI - Carbonic maceration

During the 2016 and 2017 vintages, the AWRI made small-lot Pinot Noir and Shiraz wines from single batches of fruit, demonstrating the effects of changing one winemaking variable at a time. During tastings of these wines presented across Australia, many winemakers have asked why there are such large sensory differences between wines made with 100% pure carbonic maceration and those made with the more common semi-carbonic maceration treatment or whole bunch fermentation. This column explores what is happening during carbonic maceration.

kirsch’ aromas (particularly in Beaujolais wines), but also with ‘vanilla’, ‘spice’, ‘almond’, ‘cinnamon’, ‘sandalwood’ or ‘oak-like’ characters. These characters often override any varietal fruit character, but conversely can also add aroma to wines with low varietal or fruit character. The wines are generally softer, less acidic and have lower extraction of phenolic compounds. They are reported to mature faster than traditionally fermented wines. As such, historically the technique has been recommended for lighter bodied/ fruity wines intended for early consumption. There are reports that Australian winemakers are experimenting with carbonic maceration or partial whole bunch ferments in Pinot Noir and Shiraz to produce more elegant and perfumed wines, and to aid as blending options. How do you do it? Michel Flanzy invented the original technique in 1934. A modified version, patented by Stephen Hickinbotham in 1986, involves whole grape bunches placed into a plastic bag supported by a pallet box, into which a small quantity of dry ice in an insulated container has already been placed. The plastic bag is then sealed and sometimes fitted with a one-way valve to allow carbon dioxide to escape but to prevent entry of air. Carbonic maceration character and structure occur best if grapes are kept at temperatures around 30-32°C for 5-8 days. At lower temperatures, more subtle and short-term aromas are produced, but the intensity of the character can vary depending on grape variety or wine style. Carbonic maceration takes place more readily in a gaseous atmosphere, so the volume of juice released by the berries is often inversely proportional to the degree of carbonic maceration flavour (Sneyd 1989). With increased juicing, and more aerobic conditions, fermentation What is carbonic maceration? by yeast and bacteria can occur, with the resulting flavours, and Carbonic maceration involves placing 100% intact whole those from stem contact, limiting or overriding those from the bunches of grapes, with absolutely no free grape juice, in a carbonic maceration. closed fermentation vessel filled with carbon dioxide. A range of intracellular reactions occur within grape berries that are What reactions are happening within the berry and how treated in this way. These reactions are conducted by enzymes do they affect flavour? in the complete absence of oxygen, and independent of any Carbon dioxide is absorbed by the grape berries, filling the yeast or microbial activity. The enzymatic reactions occur over berry to around 50% of its volume. Reactions within the berry, approximately a week at temperatures up to 35°C, after which which is still a living entity whilst intact, shift from a respiratory time they cease due to the small amount of alcohol produced. The to an anaerobic metabolism. fruit is then destemmed and crushed and fermented with yeast The enzyme malic dehydrogenase plays a key role in carbonic under normal winemaking conditions. maceration, by metabolising malic acid into ethanol, succinic acid and aminobutyric acid but without producing any lactic acid Why do it? What impact does it have on wine? (Flanzy et al. 1987). This results in a decrease in titratable acidity Carbonic maceration wines have a distinctive aroma and an increase in pH. which often polarises tasters. The aromas can be described as Grape alcohol dehydrogenase transforms sugar into ethanol ‘fruity’ or ‘musk-like’, with ‘strawberry/raspberry’ and ‘cherry/ and carbon dioxide. Only 0.5-2.2% of ethanol is produced,

70 Grapegrower & Winemaker www.winetitles.com.au April 2018 – Issue 651 possibly because at this concentration limited in the anaerobic environment of higher pH, elevated temperatures and the ethanol begins to disrupt the cell carbonic maceration. absence of sulfur dioxide. Additionally, membrane integrity. The quantity if a carbon dioxide-rich environment of carbon dioxide produced during the What are the effects on phenolics? is not adequately maintained, aerobic The extraction of phenolics, such first 24 hours is approximately the same microorganisms can quickly take over, as anthocyanins and tannins, from as that absorbed. again causing wine spoilage. grape skins is different during carbonic Glycerol and shikimic acid For further information contact the maceration compared to standard are produced, with shikimic acid AWRI helpdesk on (08) 8313 6600 or winemaking. While in both methods accumulating within the berry, and then [email protected] ethanol acts as a solvent for the extraction degrading to cinnamic acids, and further of phenolics, in standard fermentations, to the three main aroma compounds References a greater proportion of skin and seed Ducruet, V. 1984. Comparison of the associated with carbonic maceration: contact time occurs at higher alcohol headspace volatiles of carbonic maceration benzaldehyde (‘cherry’, ‘kirsch’, ‘almond’), concentrations than with carbonic and traditional wine. Lebensmittel- vinylbenzene (‘styrene’, ‘plastic’) and maceration, resulting in greater extraction Wissenschaft & Technologie 17(4): 217-221. ethyl cinnamate (‘cinnamon’, ‘strawberry’, of anthocyanins and tannins. Etaio Etaio, I. Elortondo, F. J. P. Albisu, M. ‘honey’) (Ducruet 1984). Other enzymes et al. (2008) suggest that with carbonic Gaston, E. Ojeda, M. Schlich, P. 2008. can produce volatile aromas that may maceration, anthocyanins diffuse from Effect of winemaking process and also contribute to carbonic maceration the skin into the pulp, which can be addition of white grapes on the sensory flavour, including ethyl and methyl seen to turn the flesh pink. Extraction of and physicochemical characteristics of vanillate (‘vanilla’), ethyl 9-decenoate any tannin into the pulp at low alcohol young red wines. Aust. J. Grape Wine Res. (‘sweet’, ‘fruity’, ‘quince’) and 1-octanol concentrations would also more likely 14: 211-222. (‘almond’/’buttery’). be skin tannin rather than seed tannin, Flanzy, C., Flanzy, M., Benard, P. Carbonic maceration wines often which could lead to a perception of softer 1987. La vinification par la maceration exhibit lower primary fruit flavours, and tannin in the wine. carbonique. Paris: INRA. this could be because the concentrations Sneyd, T. N. 1989. Carbonic maceration: of some common wine esters are lower in Are there any risks involved in an overview. Aust. N.Z. Wine Ind. J. these wines. For instance, hexyl acetate carbonic maceration? 4(4): 281-282. 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