Whole Bunch / Carbonic Maceration (CM)
“Incidental Berry Autofermetation”, “Carbonic Maceration”, “Semi-Carbonic” “Intra-cellular Fermentation” – however you want to spin it – whole berry clusters fermented in the absence of oxygen produces some incredible aromas and flavours. CM techniques facilitate early maturation red wines with distinctly ‘fruity’ qualities BUT used on the wrong variety it can have the unwanted effect of masking varietal aromas. Cabernet or Merlot are good examples of where NOT to use CM.
From a risk point of view there are a few things to consider. It’s evident that it encourages malic acid decarboxylation (great for minimal intervention winemaking – faster malo = faster stabilisation) and extracts less tannin (also good for us as we don’t use fining agents).
On the flip-side, the fruit needs to be of very high quality, handpicking is a must and fruit needs to be essentially disease free. Whole bunches must be kept intact and void of oxygen to ensure ethanol generation inside the berry commences and if stems aren’t lignified enough there is a risk of astringent tannin abstraction. Further, wine pH can increase which can encourage the dreaded Dekerra yeast not to mention increased levels of VA. If you’re gonna dance with the devil, come prepared.
So what causes the distinct aromas and flavours in Carbonic and Semi-Carbonic type ferments? The idea is that Schikimic acid accumulates inside the berry and becomes the precursor for an array of aromatic compounds – ethyl cinnamate, benzaldehyde, vinylbenzene  and ethyl decanoate for example. These compounds are considered distinct indicators of CM and present as strawberry, raspberry, cherry etc.  Done correctly, there is also less chance of ‘green’ or ‘vegetal’ aroma production as there is a reduced capacity of fatty acid oxidation in an anaerobic environment.
End of the day, it’s a fun way to make wine and something we use as a tool as opposed to a focused style year in year out. If anything, it’s an interesting discussion point at the dinner table….hell what you’ve learn’t in this post could be used as your SOCIAL CURRENCY next time the convo stalls!