This is the second of the non-Saccharomyces cerevisiae yeast that I plan to explore next season. In my first post on alternative yeast for hard cider, I covered Lachancea thermotolerans. A yeast that was misclassified for over 70 years before being identified through gene sequencing in 2003. This post is about Hanseniaspora uvarum, which is another yeast commonly found in many wild fermentation. Like the Lachancea spp., Hanseniaspora is not widely studied or understood. It has also had different names over the years. For example, it was known as Kloeckera apiculate for a time. Like Lachancea, it is also often overwhelmed by Saccharomyces strains in fermentations and is sometimes considered a spoilage yeast. However, research continues to be performed and a better understanding of this yeast is taking shape. It also offers some interesting aspects that could be beneficial for hard cider production but like most cider research, it is limited compared to wine and beer.
Like I did for the Lachancea genus, I wanted will explore the biochemical traits and fermentation kinetics of this yeast. I do not know of any commercial strains that are available. I acquired three strains from the USDA for my research. I must say that I am extremely excited to try these yeasts. Two of the samples were collected and sealed in their glass tubes in 1945. No, I didn’t make that up. One sample is from July 23, 1945, which is before the end of World War II. The other is from December 3, 1945. The last sample was packaged much more recently, 1984. Don’t say that was a long time ago! I remember 1984 quite well! I find it amazing that yeast can still be viable but I shouldn’t be. There are beers brewed with yeast salvaged from sunken Roman vessels that were laying on the bottom of the ocean. It reminds us how well equipped yeast are to survive in all sorts of extreme conditions.
The Hanseniaspora uvarum strain is commonly found in wild or naturally fermented hard ciders as well as other fermented beverages(1). It is often the most prevalent yeast found on grapes in the vineyard. However, it has been found on various animals as well as on plants and in soil. Hanseniaspora uvarum is only believed to ferment glucose. It is not shown an ability to ferment sucrose, maltose, or lactose(2). Given apples have mostly simple sugar like fructose, glucose, and sucrose, this again offers an opportunity to leave some residual sugar in hard cider. It is known to create glycosidases, which are important in creating aromas in hard cider and wine. For wine, co-fermentation with Saccharomyces cerevisiae strains are what most research advocates and is how Hanseniaspora is being assessed. In these conditions, Hanseniaspore uvarum is not found in the wine at the end of the process.
Hanseniaspora uvarum is an apiculate yeast, which means it has a cell structure with points at opposing ends, like a lemon. As, I previously mentioned many apiculate yeasts are considered spoilage yeast and some reports indicated that H. uvarum is known to produce higher levels of sulfur compounds. However, this view of it being a spoilage yeast is changing. As genome sequencing continues, our understanding of how yeast interact and impact fermentation flavors is evolving. Another example was the long-term belief that Hanseniaspora spp. are eliminated during fermentation by the production of ethanol. Since many Hanseniaspora yeast have been shown to live in solutions over 10% ABV, this belief is shifting towards killer factors produced by other yeasts like Saccharomyces being the reason the Hanseniaspora yeasts decline as fermentation progresses. Hanseniaspora uvarum is itself believed to be a potential killer yeast. Reports indicate that it is capable of limiting fungus growth like that commonly found on grapes, Botrytis cinerea or gray mold, as well as Aspergillus ochraceus, which is known to produce mycotoxins.
My Interest: A yeast that naturally can’t process sucrose, may help create larger amounts of aromas, and offers potential biocontrol of mold/fungus. I need to try that! It will be interesting to see if by inoculating it in a juice with a natural active micro flora, it can overwhelm these other yeasts, especially any Saccharomyces cerevisiae strains that might be present. Since Saccharomyces cerevisiae is less often on apples and more often on equipment, it may depend on the amount present as to whether it will be the dominant yeast at the end of fermentation. I recognize there is a risk of creating sulfur compounds like hydrogen sulfide. However, I am hoping it will consume the nutrients, make a stable hard cider with nice esters and aromas, and leave some residual sugars. It never seems to work that way but, that is the nature of experimenting. There is always a chance it might not go in unexpected directions.
Some research indicates that Hanseniaspora uvarum builds mass and ferments at a rate similar to Saccharomyces while others says it is slower. As I noted above, it is not supposed to ferment glucose, maltose, or lactose(2). M. Lorenzini and associates showed that it had residual sugars similar to Torulaspora delbruekii, around 12 grams per liter versus 0.5 grams per liter for Saccharomyces cerevisiae. Compared to Torulaspora delbruekii, it finished fermenting with slightly higher sorbitol and acetic acid(3). You might think that H. uvarum and H. osmophila would perform similarly but, M. Lorenzini found that H. osmophila was more similar to S. cerevisiae in sugar, sorbitol, and malic acid. You might also think that since H. uvarum was considered a spoilage yeast, it would be sensitive to treatments of SO2. However, N. Guaragnella and associates found that of the 26 strain they assessed 15 were not sensitive to SO2(4), which could further support the idea that treating juice with Campden may not have the effect we believe.
My Interest: My main goal remains finding a yeast (or combination of yeasts) that will allow me to naturally have some residual sugars. This would provide me a wonderful tool to create more balanced ciders from any apple. Using peels allows me to add polyphenols and color so now I just need to find a yeast that offers more control over sugar and sweetness. Using it to control other micro flora would be a bonus since I try to avoid preservatives and pasteurization. A raw or alive cider is a healthier cider from a gut microbe perspective. The very recent work being done to sequence and identify H. uvarum genes is exciting because it may lead to more readily available strains.
Unlike Lachancea thermotolerans, I have not been able to find any commercial offerings of Hanseniaspora uvarum. If someone knows of one, leave a comment so others can explore it. For now, that means you will need to go to one of the culture sites or try to culture some from a wild fermentation. Hanseniaspora uvarum is often found in hard cider that is fermented with wild or natural micro flora. Here is the list of culture collections that I have found. I am still looking for centers in other countries so if someone finds one in Canada, Australia, Africa, Europe, or wherever, please let me know. The nice thing about the USDA’s site is that you only have to cover shipping costs to obtain samples.
(1) J. Badura and associates, Development of Genetic Modification Tools for Hanseniaspora uvarum. Int. J. Mol. Sci., 22, 1943, 2021
(2) C. P. Kurtzman and M. Lachance, The Yeasts, a Taxonomic Study, Chapter 32, 2003
(3) M. Lorenzini and associates, Assessment of yeasts for apple juice fermentation and production of cider volatile compounds, LWT – Food Science and Technology 99 (2019) 224–230
(4) N. Guaragnella and associates, Genome Sequencing and Comparative Analysis of Three Hanseniaspora uvarum Indigenous Wine Strains Reveal Remarkable Biotechnological Potential., Front. Microbiol. 10:3133, 2020
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