I obtained 11 samples of non-Saccharomyces yeast from the USDA and have been conducting trials for my hard cider batches. Three of those strains where Pichia kluyveri. If you haven’t read it, I would encourage you to review my overview of Pichia kluyveri and the other strains. Just search non-Saccharomyces on the site or look for a link to the articles below. For a quick overview, Pichia kluyveri is a very common yeast that is naturally found on apples and fruit. Compared to Saccharomyces cerevisiae strains, it is a slower fermenter and is known to produce higher levels of polyols, like glycerol. It also tends to produce thiols that have tropical fruit aromas. The strains I tested had tropical fruit aromas but even more distinct was the banana aroma that each strain created. Let’s first review the approach I took for this trial and then review the results.
I used a blend of early apples and pears (60% Sweetie, 30% Akane, and 10% Hoshi Asian Pear) making three 1-gallon fermenters. The juice was treated with pectic enzyme and racked off after clarifying. I included 75 grams of the Sweetie apple peels in each fermenter. The Pichia kluyveri yeasts (y-17774, Y-11519, and Y-17228) were added after having propagated them using my standard method. The specific gravity started at 1.049 for this mixture and I monitored the ferments using my Tilt Hydrometers.
The ferment was slower than most Saccharomyces strains that I have used with mild fermentation activity through day 7. Fermentation became more vigorous at day 8 and lasted for 2 more days. All three strains had finished at 1.000 when I racked them at day 14 and moved them to storage. The temperature was in the 74-76F (23-24C) range for the ferment. Most commercial strains of Saccharomyces yeast I use finish in 4-7 days when I ferment in similar conditions. Most ciders improve with some aging but, I like to sample mine when racking to get a feel for how they fermented and how they could develop. Sometimes, the ones that I like least straight from fermentation become the ones I like best with some aging. However, after aging for 4 months, I judged the Y-17228 strain my favorite. I call this yeast “Tropical Breeze” given the fruity and tropical aromas it creates, especially banana. It will be interesting to see if this changes with additional aging. I also harvested these strains and begun reusing some for further trials.
|Strain ID||Ferment Days||Final Gravity||Clarity||Aroma||Taste|
|Y-17774||10||1.000||Hazy||Banana||Banana & Sour|
|Y-11519||10||1.000||Clear||Sulfur & Sour||Sour|
Overall, I deemed this trial a success. While a little slower, the yeast fermented to completion and the aromas were positive compared to many commercial strains that I have tried. I really liked the tropical, banana, and fruity aromas the Pichia created. While I used Fermaid-O in the propagation of the yeast, I didn’t use any nutrients in the fermentation. This year, I will ferment some with Fermaid-O added to the fermentation. I also didn’t get any measurable residual sweetness but, I wasn’t expecting it given my lower starting gravity. Some of the other non-Saccharomyces strains did finish with measurable residual sweetness, especially when I started with a higher sugar level. For now, I will be conducting additional tests with the Y-17228 strain. I am working on a cider yeast trail pack if you are interested in exploring some of these non-Saccharomyces yeast strains with me. Check The Shop & Recommended Products Page for available options or use the below button to jump to the Cider Yeast page.
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