Last season, I obtained some additional non-Saccharomyces yeast samples from the USDA-ARS Culture Collection (NRRL), which is based in Illinois. In this batch, I received two strains of Zygosaccharomyces rouxii yeast (Y-229 and Y-1294), which is a species that was positively noted in various research papers. For reference, Y-229 was found in grape must in Italy while Y-1294 was not specified. However, this species appears to be common on grapes and other fruits, so it fits with my goal of inoculating with cider yeasts (i.e. those commonly found on the fruit) as a way to create unique ciders while having more control over the process. It has even been even isolated directly from cider(1). I haven’t provided a detailed overview of this yeast before so I thought I would give you some of the basic data(2) for this species.
The yeast tends to be spherical in shape and it will ferment glucose and usually maltose and sucrose. It is not know to ferment many other sugars like Galactose and Lactose. It will usually ferment at temperatures up to 37C (99F) and is killed easily above 45C (113F). The genome was sequenced in 2000. It is often found on grapes but also frequently in various fruit jams and syrups. It is commonly used and found in the fermentation of soy products, like soy sauce and miso, and even balsamic vinegar to bring out the desired flavors. It appears to be sensitive to sorbic acid, benzoic acid, and acetic acid. At times, the Zygosaccharomyces genus was considered to be part of the Saccharomyces genus but was separated into its owns genus in the 1980s. Currently, there are seven species under this genus with S. rouxii being one. In some research, it was unable to ferment all sugars from grape, which naturally have higher levels of sugars than apple juices.
For this test, I used a 2:1 blend of sharp and sweet apples with the sharps being Arkansas Black and the sweets, Red Delicious. The juice’s starting gravity was 1.057 with a pH of 3.5, and Total Acids of 8.5g/l malic acid, so slightly acidic given the higher ratio of sharps. I fermented two three-gallon batches and added 200 grams of Arkansas Black peels in each. I included 5 grams of Fermaid-O in the juice as well. Remember Fermaid-O is a source of organic nitrogen as it is made from dead yeast. I propagated the yeast samples using Fermaid-O and sterile organic juice. I monitored the fermentation process using my Tilt Hydrometers, which I recommend on the shop page as a great tool to actively monitor your hard cider.
Zygosaccharomyces rouxii is known to be a weaker fermenter leaving residual sugar in wine. I find for cider that many non-Saccharomyces yeast are capable of finishing the fermentation. I also find they still tend to produce a cider that has more sweetness to it. This is usually from the creation of more glycerol by the yeasts. This yeast was slower to start and had fermented between 20-25 points after 14 days. This is slower than most Saccharomyces cerevisiae strains but a great rate for a warm ferment (23C/74F) as it helps retain more of the aromas. After 21 days, the cider was clearing and Y-229 had dropped to 1.010 and Y-1294 to 1.000. Y-229 finished fermenting at 1.000 after another 7 days. I bottled them with 2.2 volumes CO2 and starting sampling them after 3.5 months. I have also included these on an accelerated aging trial that I am doing. I received mixed favorites from my tasters with regards to which strain was their favorite. Both are clear and have a comparable color, Y-1294 was deemed to be sweeter and less bitter, but that bitterness was appreciated by some. Overall, both were deemed “good” by all tasters.
| Strain ID | Ferment Days | Final Gravity | Clarity | Aroma | Taste |
| Y-229 | 27 | 1.000 | Clear | Fruity | Bitter Apple |
| Y-1294 | 20 | 1.000 | Clear | Very Fruity | Sweet Apple |
This yeast has many promising characteristics. The slower but complete ferment with a higher level of perceived sweetness has good promise as a cider yeast. It makes a very good cider using non-bitter apples. Like most of the non-Saccharomyces yeast, these produced ciders that were more flavorful than most ciders I have made with Saccharomyces strains. I selected Y-229 to propagate initially because of its potential to leave more residual sweetness and the more complex notes it had. I am offering this through the Cider Yeast page for others to try. I believe you will appreciate the complex aromas and tastes this yeast creates, even with common apples. After my extended aging trails, I will assess them again but cider made with these yeast appear to be improving with age.
(1) A. Gschaedler and associates, Use of non-Saccharomyces yeasts in cider fermentation: Importance of the nutrients addition to obtain an efficient fermentation, International Journal of Food Microbiology, 347, 2021
(2) S. James and M. Stratford, The Yeasts, a Taxonomy Study, Descriptions of Teleomorphic Ascomycetous Genera and Species, Zygosaccharomyces, Ch. 84, 2011
I have created some trial packs of non-Saccharomyces strains if you want to test some as well. You can find them on the Cider Yeast page in the The Shop. I also included the following button to go directly to the yeast page.
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