FERMENTATION IN WHISKY

We unpack this under-appreciated, yet crucial aspect of whisky production.

Fermentation beaker sample, courtesy Waterford Distillery.

To say fermentation is fundamental to spirit, or any alcohol, is an understatement.

All whisky is a beer (which is technically a fermented grain beverage) before it is distilled into new make white spirit, ready to be matured in barrels. One simply cannot discuss fermentation without discussing yeast.

Brewers or distillers yeast is a most wonderful organism. A single-celled organism, which shares some properties of the animal and plant world, though it is technically a plant, belonging to the fungi kingdom. It can exist and thrive in both aerobic (with oxygen) and anaerobic (without oxygen) environments. To make a beer prior to distillation in a distillery, it is the brewer’s job to extract and breakdown the starchy sugar from the barley grain into simpler sugars that a yeast cell can digest. And when I say a yeast cell, I’m actually talking about as many as a trillion yeast cells per 200L of beer. The yeast cells, when presented with this lovely sugary extract from barley, set about multiplying, and then digesting sugar, and converting it to C02 gas (very bubbly fermentations), ethanol (thanks yeast cell!), and some other by-products like esters and other compounds, which may or may not have flavour and aroma characteristics.

Yeast cells in replication, known as budding. Courtesy, Waterford Distillery.

Fermentation has not featured much in the marketing parlance of whisky brands. Is it not a sexy subject? Traditionally, commercial distiller’s yeasts, which have been isolated and banked for commercial production, have been valued for their efficiency in alcohol production, and alcohol tolerance. The more alcohol they can produce in the beer, the more alcohol yield you will have through distillation. Different distilleries will have different yeast strain preferences, based on their specific objectives, some of those objectives will be the flavours the yeast produces as a by-product of fermentation. And here lies the crux of this article, because it is this author’s opinion that a lot of (sexy) innovation and excitement lies in pursuing expanded fermentation options in whisky.

To make a flavourful beer, that you would choose to drink as a beer, you would not use a distiller’s yeast. You would probably use an ale yeast, for its superior flavour and roundness. It makes complete sense to me, then, that we are seeing some progressive artisanal whisky brands in emerging markets like Japan and the USA, not only do more innovative things with fermentation, but also talking about their fermentations as a point of differentiation. Slower, controlled fermentations can be responsible for preserving or elevating the subtle flavour from the raw material, barley. Ireland’s Waterford distillery are particularly vocal about expressing barley, and about their fermentations, for that matter, and for good reason. I can taste some unique expression of barley in their spirit, from highly controlled and slower fermentations.

All hail the humble yeast cell, and the process of fermentation, where would we be without this? I anticipate an emerging focus towards fermentation among more progressive brands, and we are already starting to see this from Japan and the emerging American Single Malt category.