Whisky Magazine Issue 21
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The influence of yeast on the final flavour of a whisky is hotly debated within the industry. Ian Wisniewski takes a closer look at whisky's most active ingradient.
The hardest worker in any distillery has always been yeast, according to traditional staff humour. But then yeast's job description has always entailed two vital functions performed simultaneously: converting fermentable sugars into alcohol, while also creating a range of aromas and flavours beyond wort's integral cereal characteristics.
Needless to say, the influence of the yeast also depends on other contributory factors, including the sugar concentration in the wort, the pitching temperature and rate of fermentation, not to mention distillation and maturation.
As different types of yeast are believed by some distillers to promote varying flavour compounds, deciding which to use can be significant. This means a choice of either distiller's yeast, with Quest M developed in the 1960s for example, or the more historic option, brewer's yeast.
Being a cultured yeast, often cultivated using sugar such as molasses, principal strains of distiller's yeast include Quest M, Quest MX and Mauri Pinnacle, with so-called ‘fast acting' and ‘slower acting' strains available. These behave as you would expect, with some distillers
combining both to promote more sustained action during fermentation.
Whether to use fresh or dried distiller's yeast is another consideration. Fresh yeast is typically used in a ‘pressed,' also known as ‘caked,' format, with the yeast drained of liquid and pressed into a cake. This keeps for up to two weeks when refrigerated, at an optimum temperatu...