Yeast – from East to West
Every whisk(e)y distiller relies on yeast to convert the sugar in the wash/mash to ethanol, which is then distilled in the stills. Granted yeast is but 1 factor, however fundamental, in a litany of variables in which the choices made would affect the character of the new make – For instance in the fermentation stage alone, consider wooden vs steel washbacks, capacity of washbacks, temperature of fermentation, length of time for fermentation, pitching rate of yeast etc. And let us not get into the subject of barrels. But how curious it is that the practice over and the attitude towards yeast seems to vary so greatly around the whisk(e)y world.
First – a word on yeast itself. Yeast is essentially unicellular fungi, of which approximately 1,500 species (comprising about 1% of all yeasts) are known to man. From this pool we get some particularly nasty fellows we ourselves as a species invent all sorts of medicines to combat, but we also raise some benefit from one Saccharomyces cerevisiae (and a few close relatives) – the yeasts responsible for fermentation, without which there would be neither bread nor whisky.
The job yeast needs to do is no mean feat for single cell organisms. It needs to produce as much ethanol as possible, without actually getting killed by it, and it needs to do it as quickly as possible while tolerating a wide temperature bracket, and be resistant to other undesirable yeasts, and infections, above all it has to be consistent in this age of industrial production. The literature never lists addition to flavour very prominently in the job description, and in fact there does not seems to be any clear consensus whether yeast actually contributes to flavour or not.
The Japanese, with their rich history in sake, reverently believe so. Distillers there cultivate a library of available yeasts, employing one or several different strains to achieve different characteristics in the new make. But of course Japanese distilleries are also well equipped to vary most other facets of production as well, and actively do so to produce a variety of styles.
The Irish are less convinced, Midleton (Midleton, Powers, Paddy, Jameson, Tullamore Dew) employs a standard 2 strains of brewer’s and baker’s yeast for all the whisky they distil, blandly described as ‘a traditional type of distilling yeast’. The Irishman (of The Irishman range of whiskey) describes yeast used by the Irish whiskey industry as ‘always the same type and it is not considered to impact on the flavour.’ On the other hand, Irish distillers may use enzyme additions to improve efficiency in washes with low amounts of malt, might alterations to the wash’s flavour be due in part to that as well?
The Americans with their links to the Irish and Scottish distilling have done a one-eighty and taken cultivation of yeasts to a puritanical extreme. Fred Noe and Jimmy Russel, Master Distillers of Jim Beam and Wild Turkey faithfully cultivate the same yeast daily – in Wild Turkey’s case, the same yeast cultivated for six decades. There is a firm belief in mashbill, yeast and tradition in these parts, the same tradition which saw yeast prepared by simply ‘placing a nutrient solution below a pear or apple tree.’
Alltech, an American biotech company has gone so far as to take this back to Ireland by opening an Irish distillery that will use the company’s specially derived strain of distilling yeast. And yeast is even a selling point with the Four Roses ten recipe bottlings series – 2 different mashbills and 5 different yeasts resulting in ten different bourbons. I wonder if this idea has reached the ears of that one man of Tain where it might ferment into yet another glorified NAS offering.
Coming back to the Scots – By and large the Scottish distillers obtain their yeast from the large yeast suppliers – Malt distillers rely on Kerry Ingredients and Flavours for the Kerry ‘M’ and ‘MX’ strains, and Mauri Products for the Mauri Pinnacle strain, and for grain distillers, British Fermentation Products provides an unspecified high yield yeast. A minority are still using brewer’s/other unspecified distiller’s yeasts. Also somewhat common is the practice of mixing in a percentage of another yeast so that 2 strains are used, as there are some synergistic benefits, the science of which is beyond me, for example Bruichladdich uses M and a portion of Mauri, and Macallan uses Mauri with M and some brewer’s yeast mixed in. (Udo) However as far as possible, a distillery will rely on the same yeast strain/formula/pitching ratio from run to run in the interest of consistency.
How did the Scottish distillers get to this point? The history of yeast use is not well documented, but the development of the industry may yet provide answers:
It can only be surmised that the earliest distillers carried forward yeast inocula from batch to batch… As distilling progressed into an industrial scale operation, it is well documented that distillers made use of surplus yeast from the brewing industry. The development of large grain distilleries created a massive demand for yeast, and it became common practice for the larger distilleries to propagate their own strains. Specialist yeast factories then evolved from these grain distilleries producing cultured yeast specifically for that distilling industry…
Inge Russel, Whisky: Technology, Production and Marketing (Handbook of Alcoholic Beverages)
So today’s yeast strains do seem to have its roots in whisky distilling, and the commonality in yeast choices does reflect the ultimate similarities in Scottish distilleries climate and malt distillation regimes: The old DCL ‘M’ strain, precursor to Kerry’s ‘M’ strain, was already widely used in the 70s, along with recycled brewer’s yeast. Though brewer’s yeast is no longer used as much ‘when it was realised that its quality and keeping properties had declined to such an extent that it was no longer viable as a fermentation supplement, either for ethanol production or for flavour quality.’ (Graeme Walker, Tom Bringhurst and James Brosnan, “The Ideal Distiller’s Yeast?”) Also it should be added, that modern strains promised better economic returns to the distiller.
Lastly it should be noted that this facet of distillation is far from stagnant – companies are investing heavily in research, looking for better performing yeasts, as it is after all tied to the bottom line. One only hopes that next to consistency, quality of flavour should also rank highly as a priority.
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