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Quite a few years ago, while presenting at a rum industry educational series in Jamaica, I was told of a single malt distillery that intermittently used a fission yeast. Besides wine industry use, some one at Lallemand had told me that the only interest they had ever received for fission yeasts was in single malts. And here we are today. Callum Upfold provides us an incredible case study which is his Grenada fission yeast single malt produced in New Zealand. The Grenada yeast is just one from his fission yeast collection. I was nervous about analyzing this spirit because I had never surveyed a single malt with the birectifier. I had no good frame of reference. We thought a win might simply be discovering abnormally low fusel oil and zero off aroma. This distillate was an easy win, but also went a step further.
Fission yeasts produce far less fusel oil than budding yeasts which can be extremely valuable in general but also in hot conditions where the inability to cool the ferment can push fusel oil to gross surplus with a budding yeast, thus compromising less volatile high value aroma. This may be increasingly valuable as climate change advances, but also as single malt production pushes into more southern warmer regions or continues through the summer where previously distilleries took a break.
Fission yeasts are also known to produce off aroma in grain which has led some to abandon their exploration. We have found that off aroma can be mitigated with careful nutrition and there are some strategies tailored to fission yeasts that do not fit a budding yeast. Callum easily avoided off aroma.
Where this distillate went a step further was when we finally discovered that the Scottish single malt distillery intermittently using a single malt was Glen Elgin (hat tip to Andy at Stone Barn Brandy Works). The dominant character of Callum’s single malt matched descriptions of Glen Elgin which I’ve never come across. Bits of other information came in, such as Dave Broom was aware that a few other distilleries had trialed fission yeasts with the goal of developing “green apple” character for use in blends. I did not get a green apple note, but I did get a radiant honey note and remarkable persistence.
Sweet to start, then fruity, Glen Elgin whisky is a typical Speyside – complex, fragrant, with a delicious orange blossom finish.
Douglas Murray of Diageo says:
“In Glen Elgin, the bulk of the character is created before it goes to the still”
It is widely acknowledged that Glen Elgin is important to the Whitehorse blend, but also that it is important to other blends. Anyone want to wager if a special yeast makes it special stuff?
Callum’s single malt featured Vienna malt and Chit malt from Gladfields in NZ. The starting pH was 6.5 and the final pH was 4.5. Fermentation lasted 8 days and fruity throughout with no sulfur or off aroma.
Fraction 1: Very light with no non-culinary aroma. Possible aroma from grain?
Fraction 2: Less concentrated version of fraction 1 as expected.
Fraction 3: Very neutral as expected.
Fraction 4: Slightly cloudy on visual inspection. Unique amount of precipitates floating at the top. Detectable high value fraction 5 character. Definite presence of fusel oil, but light and inline with a fission yeast. Fascinating character on the palate I’m attributing to high value character that started early. Luxurious dense sort of character. No doubt the malt contributes something. Despite the significant amount of fusel oil supposed to be in this fraction whatever high value character that came over early is enough to smother it.
Fraction 5: Visually clear. Very different than the typical fraction 5 possibly because much of the aroma came over early. Slight earthy character. When preparing this fraction earlier I thought I recognized the honeyed character of the distillate, but I’m not so certain now. A possible type of rum oil/rose ketone? There is a sensual character. More plain on the palate, no distinct gustatory acidity.
Fraction 6: Very clean with no off aroma or gustatory acidity. Subtle non-specific character, but no significant aroma.
Fraction 7: Even cleaner and more aqueous than fraction 6.
Fraction 8: Identical to fraction 7, zero off aroma and extremely clean.
Thank you Stephen, it was very fun to make. I can see some easy improvements to make as well. Stay tuned for an optimized high rye Bourbon.