As I noted in my Mâlus Trivium post about potential alternative yeast for hard cider, there are several I plan to trial for the next season so I thought I would highlight each. One of those is Lachancea thermotolerans. The Lanchancea genus is a relatively newcomer from a classification perspective. In 2003, a new multi-gene sequencing strategy enabled scientists to better classify yeast(1). The Lachancea genus was created and this quickly grew to include 11 species and more may be identified. For almost 100 years, this genus of yeast has been mislabeled. Beginning in 1928, one of the Lachancea strains, L. fermentati, was placed in the Z. fermentati genus. That was followed by numerous other strains in this genus being mislabeled as Zygosaccharomyces spp., Kluyveromyces spp., and Saccharomyces spp. Remember the yeast genome sequencing I discussed in my post on yeast DNA? This work is allowing us to understand our world at a new level and better classify yeast at a genetic level versus other methods.
T. Porter and associates assessed several strains of the Lachancea genus and identified several key characteristics(1). I decided to focus this article on the L. thermotolerans strain because I have three experimental strains that I plan to use to ferment my hard cider next season and I want to get some expectations about how they will work. I also thought it would be worthwhile to share more about these yeast so you could decide whether they sound interesting enough to trial. I wanted to explore the biochemical traits and fermentation kinetics, arguably the two most important aspects for hard cider makers. I also wanted to discuss where you can source this yeast for your own trials and assessment.
The Lachancea thermotolerans strain is found in many areas of nature. It is often found in grape must (juice) as well as many other fruits. It is been identified in lake water, cocoa fermentation, and olive paste and pomace(1). Lachancea thermotolerans is known to ferment both glucose and sucrose while maltose, not found in apples but interesting for beer, is variable(2). It is known to assimilate raffinose, ethanol, and mannitol. They are typically not able to assimilate nitrate, lactose, soluble starch, methanol, and erythritol. That means you could back sweeten with erythritol and it won’t ferment or process it into something else. One very interesting aspect is that It appears to assimilate trehalose, which is a sugar consisting of two glucose molecules. However, a yeast’s ability to assimilate or metabolize trehalose has been an indicator of that yeast’s ability to survive stressful conditions. This has been demonstrated for Saccharomyces spp. It stills need to be proven for Lachancea spp(2). Anecdotally, some Lachancea thermotolerans strains have been found in wine at the end of the fermentation when it is co-fermented with Saccharomyces, which indicates its ability to survive stressful environments. More research is definitely needed to understand this trait. The final biochemical trait that has been identified is that some Lachancea yeasts produce toxins that eliminate fungi and inhibit some bacteria(3). These killer factors are interesting because they may provide better natural stabilization.
My Interest: These characteristics make me hopeful that by inoculating with Lachancea thermotolerans, it will overwhelm my natural micro flora, become the dominate strain, and finish the fermentation. I am hoping that it will be capable of dealing with the stressful environment of apple juice and outcompete others by consuming the nutrients and potentially having killer factors that will remove spoilage and maybe even inhibit Saccharomyces spp or other naturally occurring yeasts.
Lachancea thermotolerans is generally a slower fermenter than Saccharomyces cerevisiae and even though it can ferment both glucose and sucrose, it is known to leave residual sugars(1). This is why many commercial strains for wine fermentation use a combination Lachancea and Saccharomyces yeasts. However, for hard cider, leaving some residual sweetness makes this an interesting option. Most yeast is packaged for either wine or beer, which have much higher starting sugars or complex malt sugars. Even the Lachancea available commercially is marketed at wine makers. Lachancea thermotolerans is known as a producer of lactic acid. In hot regions where acids in grapes are reduced, it is considered a good yeast option because it can increase titratable acids through the production of lactic acid. For apples, it can also convert a decent amount of the malic acid to lactic acid. S. Benito reported from 8-26% of malic acid being degraded(3). This could be beneficial for taking the bite out of sharper apple blends.
My Interest: I would love to find a yeast that allows me to naturally control the level of residual sugar. I like dry and semi-dry hard cider but being able to retain a touch of sweetness can make the difference between a good cider and an awesome cider. Since I want to avoid preservatives and pasteurization in order to retain more healthy micro flora in my hard cider, I am hoping Lachancea may be part of the key to this path. I also find it’s ability to degrade malic acid to lactic of interest because I sometimes have high acid apples.
Most commercially available strains are co-fermentation mixes but there are some single strains options. I acquired my samples from the USDA through their website. These require creating a starter and growing it up to meet my batch sizes. If you are seeking options to try, check some of the commercial sources. CHR Hansen has several blends but their Concerto is 100% Lachancea thermotolerans (what used to be called Kluyveromyces thermotolerans). Also, Lallemand offers Philly Sour, which they market as a souring yeast because it generate lactic acid.
(1) T. J. Porter and associates, Lachancea yeast species: Origin, biochemical characteristics and oenological significance, Food Research International 119, 378–389, 2019
(2) C. P. Kurtzman and M. Lachance, The Yeasts, a Taxonomic Study, Chapter 41, 2003
(3) S. Benito, The impacts of Lachancea thermotolerans yeast strains on winemaking, Appl. Microbiol. Biotechnol. 102, 6775–6790, 2018
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