Marissa Neuner: Liberating the microorganism

Photo: Contributed

We’ve all read the “tortoise and the hare” fable - slow and steady wins the race. This parable has been a quiet, guiding force throughout my own life, reminding me that true callings require patience. The road of transparency and honesty while slow, is an allegory for life itself.

I’m drawn to wild fermentation - in a way, it is symbolic of my personal beliefs. Wild yeast populations exist everywhere. If given the opportunity to proliferate and ferment naturally, their expression is much different than those found in lab selected yeasts used in conventional winemaking, not to mention significantly slower working than their commercial counterparts.

It was with much giddiness when I was connected to Marissa Neuner, who has completed a master’s thesis on wild fermentation. I had the chance to speak with her recently, and we excitedly shared our passion for a relatively undiscovered and not oft discussed process in winemaking.

Marissa runs her own company based out of the Okanagan, which you can learn more about here.

LM: How did you decide on a masters in wild fermentation? What was so enticing or intriguing about it?

MN: Originally I knew I wanted to study yeast from a BC wine perspective, and after looking into the existing research I very quickly found out that all the focus had been on researching yeasts from a spoilage perspective, or a purposeful inoculation perspective. Hardly anyone had looked into yeast populations in spontaneously produced (my nerd version of natural) wines, or the resultant chemical and sensory attributes that made them differ from inoculated counterparts. What was most enticing was the idea that natural wine was the quickest route to uniqueness and true terroir for a winery. All the work in the vineyard wasn't cancelled out by mass yeast monocultures, and instead invited native cellar and vineyard yeasts to take a more prominent role in the ferments and impart chemical nuances that directly reflected the specific winery and vineyard of origin. LM: Can you share in depth all the discoveries you made ?

MN: Firstly, and most obviously, was that microbially, chemically, and sensorially, spontaneous ferments differ 'wildly' (ha, natty yeast pun😋) and significantly, from ferments done with purposeful inoculation, despite the ferments coming from the same vineyards, treated the same way, and undergoing the same cellar conditions/ferment parameters. 

Microbial: The natural ferments took longer to reach completion, regardless of whether they were tank or barrel ferments, and at all stages of fermentation the diversity of yeasts present was increased in that unidentified, noncommercial yeast strains made up 1-6% of the overall yeast community. Inoculated tanks had fewer than 1.5% of their overall yeast community composed of unidentified non-commercial strains. Now, while this does not seem like a lot, keep in mind these are commercial winemaking cellars, full of commercial products, yeasts, and cleanliness strategies, meaning that these 'natural' wines had years of inoculation to contend with. The yeast communities in all spontaneous fermentations were dominated by specific, and very regularly used, yeast strains present in other fermentations within the wineries; however, the number of yeast strains present in a spontaneous wine is greatly increased over inoculation. So, despite many commercially available yeast strains playing a dominant role, there were a greater proportion of yeasts present in natural wines vs inoculated, and it was also inhabited across all stages of fermentation by more non-sacchoramyces species than expected. In fact, the yeast genus Pichia, was capable of existing and metabolizing grape must even at the high alcohol phases of ferment, indicating that they are much more hearty than previously thought and could definitely be contributing to the chemical makeup of those wines. In our lab, a colleague developed a chemical marker that differentiates living from dead yeast cells, so sequenced yeasts are all 'viable' at the stage of ferment they are identified, showing the yeast populations at each sample stage were actually living within the grape must and therefore capable of influencing the overall chemistry and sensory attributes. This research was conducted at numerous wineries, across numerous varieties, to similar results, and covered cellars that were 1-10+ years old, and in each instance the spontaneous ferments were dominated by many different previously or concurrently used commercial inocula, showing that their 'natural' wines were actually co-fermentations of many purposefully chosen and very competitive yeast strains, limiting any real risk of a spoilage organism taking hold beyond the competitive edge of commercial yeasts.

Chemically: Overall, the chemical attributes of spontaneously produced wines were more diverse, less concentrated, and significantly different from their inoculated counterparts. Acidity, residual sugar, and final alcohol content of the wines were not significantly different, however GC-MS analysis showed correlation between the Pichia yeast populations and a higher amount of Isoamyl acetate in wines with this yeast. Despite it being a 'spoilage' compound, implementing a banana aroma into wines where it predominates, it wasn't produced in an amount great enough to breach detection thresholds therefore it wasnt contributing negatively.

Sensory: The resulting textures, aromatics, and palate descriptors of the spontaneous vs inoculated wines were shown to be significantly different when tasted blindly by a panel of 10 judges across 6 ferments. Spontaneous wines were shown to be more delicate in the presence of each descriptor, they were scored higher on consumer liking, and they detected a greater number of descriptors than inoculated wines. All panels were conducted on wines that had not been sulfured following fermentation, and had not yet undergone malolactic fermentation, but intended to.

Photo: Contributed

MN: I basically decided right away that any wines I made needed to have the freedom of a spontaneous element. I know from my 3 years/vintages of research that in no case did a spontaneous wine made in these cellars 'stick' or be commercially non-viable in the end product. The companies I went to work for have successful portfolios and very distinct styles, however they all valued the notion of 'terroir' since they were making many of the same wines as their neighbours, so I wanted to pay homage to the house style, but use my instincts in understanding yeast microbial dynamics and their aromatic cues to limit the use of commercial yeasts where appropriate to truly make a wine of distinction that reflects that cellar and vineyard. It made me a braver, more knowledgeable winemaker, and gave me a sense of trust in my senses that I used in each vintage.

LM: What are some differences stylistically between inoculated ferments and wild ones? Do you have a preference ?

MN: Inoculated wines typically lean more 'true to variety' than spontaneous ones, because the grape chemistry is highlighted by a yeast strain that has been developed to highlight it. Wild ferments instead select for yeasts that are best suited to the environment they're in, and they interact with the grape must in a way that can produce compounds that influence the palate and aroma in more unique ways, expressing the variety differently than many people have tasted. I prefer natural wines because it truly shows the skill of the winemaker, as they didn't follow a 'recipe' of sorts, instead they relied on their instincts, past experiences, and their senses!

Photo: Contributed

LM: Can you explain to non industry people key differences, and why it’s such a controversial topic ?

MN: It's controversial for two reasons I'd say - first, people assume 'natural' is risky, and therefore they don't want to waste a year’s worth of viticultural input and a season’s worth of cellaring to make something that will ferment at whichever pace it ferments, and may allow a spoilage organism to take hold. In an industry where profit margins are slim, and competition is huge, it's difficult to justify the potential loss of profit for the creativity of a natural wine and causes many a challenging conversation between winery owners and winemakers. Second, it's controversial because the consumers have been underexposed to affordable natural wines. Because of the time and effort that's gone into more detailed grape growing and the longer alcoholic and malolactic fermentation stages, the natural wines tend to have a higher price point and are marketed in a way that doesn't attract the everyday drinker, and is more for the experience wino who can appreciate the experience in that bottle. Mass produced and more commercially friendly wines can be made cheaply, reaching many more people, so their idea of what grape varieties are meant to taste like is totally skewed. LM: Can you share info on all the yeast strains and populations you discovered ? Did they behave differently? How so?

MN: Yeasts are incredibly hearty organisms, and they are ubiquitous in the environment - not just in cellars. Their diversity is influenced by many factors, like pH, alcohol levels, temperature, and competition with other microorganisms, so it is very unrealistic to expect yeast populations in real life settings to be reproducible or consistent like they can be in the lab. Overall, inoculated fermentations showed lower yeast strain diversity than spontaneous, and the inocula strain took a predominant role in all stages of fermentation, as was intended; however, some yeasts are more competitive than others, and it was found that specific yeast strains that havent been used in years are able to persist in the cellar environment despite intense cleaning practices and enter ferments in a significant way. This suggests that winemakers really need to understand WHY they are choosing the yeast inocula they do, because they're capable of sticking around even when you no longer want them! Introducing such a competitive organism into cellars can influence future vintages, and you have to be absolutely sure it suits the wines you're looking to make. Once you go commercial, it's near impossible to go back.

LM: What’s been in your glass lately?

MN: I've been going through a lot of BC Pinot, and drinking barrelled Viogniers that aren't trying to mimic any of the prototypical European styles. Some standouts are the 2018 Viognier by TH wines, any of the clone specific Pinot offerings from Spearhead Wines, or the unfiltered and unfined Pinot from Nichol. I'll never shy away from a juicy Riesling, Gamay, or some Pet Nat either!  LM: How can we appropriately educate more people on drinking higher quality wine?

MN: I think on the whole, we just need to remember that mass production, while easier on the wallet, tends to shy away from highlighting the true skill an artfully made bottle of wine can express. Consumers are drawn in by flashy marketing, gorgeous tasting rooms, and the drama of the giant cellars, but I've always found it’s the little guys, who have everything on the line and typically their whole family involved, that make some of the most interesting and memorable wines. 'Quality' is a tough word, because I think it is highly biased by personal opinion. A wine I find to be high quality, means that thought was put into every single stage of the grape’s existence, from pre-planting to bottle. And to drink those, typically it costs a little more, you have to look a little harder, and it may not exist from year to year if the conditions aren't perfect. It's all about making sure consumers include wineries that are off the beaten path, that have a history or a really clear farm-to-bottle mentality, where you'll find the true gems worth sharing. LM: Are there farming practices that result in healthier yeast populations?

MN: YES. Gosh.

The vineyard is dominated by a class of yeasts called non-Saccharomyces, which basically just means that the majority of the yeast genus' present on grape tissues is non-fermenting (or so we THINK). They are generally inert in inoculated ferments because typically wineries who make inoculated wines also follow a rigourous spray schedule which involves fungicide on the regular, killing a lot of the yeast (which are fungi) and preventing blooms from forming that persist during crush. BUT, as with most things, the more you spray, or kill, the more you are selecting for the big baddies that are capable of really messing something up! Vineyard managers may be unwittingly selecting for really strong, really influential yeasts (as may have happened with the Pichia species I detected in my research) by spraying their vineyards relentlessly, instead of focusing on managing the grapes with organic/biodynamic or more manual practices. Also, since Saccharomyces cerevisiae, the fermentation yeast, isn't as populous in the vineyard, by overspraying or conventionally managing a vineyard with fungicide, you are killing them off in greater abundance, preventing those house strains from entering into ferment and allowing for a terroir focused effect in any of your wines.

LM: What’s next for you?

MN: I branched out on my own and started a beverage analysis and fermentation consulting firm called Cellar Door Analytics. My goal is to take the analytical side from my Master's, combine it with my years of production and vineyard experience, and elevate the BC beverage industry beyond just wine. I've always been an avid consumer, and I'm a big believer in supporting local since we make some killer products out in BC, so I've been consulting and working with winemakers, cidermakers, brewers, distillers, and kombucha makers to support their fermentation goals. 

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