Why does every wine taste mousy now?
By: Jeff Segal
Tags: Farming, Food And Beverage, Wine, Climate Change, Science

There’s something that’s been taking up space along the margins of my sanity over the past few years. It began in earnest in 2016. Every wine suddenly started tasting mousy. I’m being a bit hyperbolic, but only a little. And it’s been an unrelenting ascent since then. I taste multiple mousy wines every single day at this point. Then, a few months ago, I hit a breaking point when I opened a new vintage from one of my favorite producers in the world and it was undrinkable.

If you’re uninitiated with the wine fault that is mouse, here’s the elevator pitch. It’s a compound called tetrahydropyridine (THP for short) that makes wine taste like the inside of a mouse cage or, at best, stale cereal grain. It’s not aromatic until it comes into contact with saliva, so you can’t smell it. And somewhere between 30–50% of people can’t even taste it due to the relative pHs of our mouths. Personally, I hate it. It quickly takes over a wine; once it’s there, all I can taste is mouse cage (at least my brain’s rendering of a cage with a mouse residing inside of it).

The first time that I really remember tasting mouse in a wine was in 2007. It was an Aglianico from Cantina Giardino (a producer that I love, I’m actually drinking their Volpe Rossa while writing this). I remember turning to somebody and asking if they too thought the wine tasted like rancid Captain Crunch. They looked at me like wtf is wrong with you and finished my bottle.

I asked Lee Campbell — natty wine OG, wine consultant, sommelier — when she first recalled tasting mouse. She said, “I wish I could know the first time I tasted mouse. It’s like one of those ‘tree falling in the woods’ things. Was it definitely present in some of the first natural wines I tried in the early aughts? I know there were stability issues with the wines, but when did we designate mouse as a particular characteristic? Here’s what I do know…sometime in the early aughts, Alice Feiring started calling mouse, ‘puppy’s breath.’”

But Lee thinks that mouse really started to become a thing a decade or so later. As she put it, by 2012, “mouse was now demanding to be taken SRSLY. We were beginning to feel encroached upon. This shit wasn’t going away.”

And then, like some zombie movie where the characters start to debate whether life really is better when they eat flesh, the narrative shifted. People started to defend mouse. Like, really defend mouse. Mouse became some kind of aesthetic choice, a variant on how we expect wine to taste, an expression of umami. This is how wine used to be before our palates became commercialized. It’s real wine. It’s art. Mouse is authenticity.

Whether you’re a believer in mouse or not, it’s pretty clear that mouse is just more prevalent now. Natural wine presents so many possible explanations: the zero sulfur movement, the rise of carbonic maceration, insatiable demand for glou glou, sloppy work by new winemakers looking to become friends with Action Bronson.

And then there’s a factor that has nothing to do with natural wine.

Pascaline Lepeltier — one of the figureheads of natural wine in the US and the first woman to win the Best Sommelier of France award — points to our changing climate. She says that mouse isn’t the problem, it’s “in fact a symptom that we can taste of what’s changing in the world around us. Climate change is affecting our yeast and bacteria populations.” According to Pascaline, mouse always existed but its recent uptick is primarily about the confluence of three factors: the evolution of farming, less intervention in winemaking, and the effects of warmer temperatures on wine grapes. Climate change is creating different microbiological activities while raising the pH of wine grapes worldwide (giving them less bacteria-neutralizing acids), right as winemakers are trying to be more hands off in the vines and the cellar.

One specific intervention (or lack thereof) that Pascaline points to is the use of less copper and sulfur in the vineyard and the winery. That likely has consequences on the inhibition of certain bacteria at a time when higher grape pHs also mean there isn’t a built-in environment to regulate them. When you couple that with practices like more lees involvement — aka: integrating the dead yeast cells and other spent particles that settle after fermentation back into wine — and other oxygenating factors (the oxidation of alcohol coming from riper grapes is an important trigger for the production of mouse), you’re talking about a perfect environment for certain yeast and bacteria at a critical time in the life of a wine, i.e. during fermentation.

Winemaker and sommelier Raj Parr says he’s made over 1,000 cases of zero zero wine and hasn’t dealt with mouse, which he attributes to keeping his cellar at 55 degrees, being very careful with oxidation, and, most importantly, harvesting grapes with low enough pHs to not require sulfur. Raj points to the same intersection of high pH bacteria and cellar practices that only worsen the problem. He specifically looks at the trend toward winemakers, “not topping up wines and making wines in warmer cellars, which affects dissolved CO2 and plays a big part in the microbial balances of the wines, especially when there are higher pHs involved.”

Fellow California winemaker Martha Stoumen looks at a much more specific climate-related factor: higher grape pHs (again, from higher temperatures) forcing wines to go through malolactic fermentation before they’re finished with their primary fermentation. This gives them plenty of sugar with no malolactic acid left — a dream scenario for hungry bacteria. As Martha puts it, “it makes sense, the bacteria have lots of food to eat and nothing to stop them.” She’s seen this in two of her wines, her only two wines to ever be mousy, both of which she turned into brandy (“luckily it turns out that mouse doesn’t distill”).

I asked Martha specifically about California and why there seems to be less mouse there. More sulfur used to be the obvious answer, but there are plenty of zero zero producers out West now. She points to relatively low pHs, especially in coastal areas, and the presence of tannins. Indeed, in my own experience, tannin may be mouse’s magic bullet. I’ve tasted very few wines with both grippy tannins and mouse. But Martha says that California’s move toward increased carbonic maceration might threaten its relative paucity of mouse. Carbonic leads to an environment that really favors active bacteria: less malic acid, plenty of sugar, and yeast slowed down by colder fermentations. It’s taken off because of natural wine’s love of, as Martha puts it, the “aroma-driven, featherweight style,” which now has even classic winemakers suppressing the things that help regulate active bacteria in wine, like acid and tannin.

I wanted to talk to a brewer, as they understand bacteria and high pH environments better than anyone, so I reached out to Joey Pepper, the head brewer at Folksbier, because a) Folksbier Glow Ups are straight manna for Domestique, and b) he’s also really into natural wine. Joey said that in beer it’s all about controlling THP, either by producing beer where it’s kept below threshold through multiple fermentations, or by allowing for enough time before release for it to clear up. As for wine, Joey thinks that, “wines simply aren’t given enough time to correct themselves or even put in the position to do so.”

Whenever we get a mousy wine at Domestique, we put it away in the cellar and revisit every few months. What you find is that the bottles taste different each time — the mouse is in constant evolution, waxing and waning along with the other elements of the wine. Raj says that’s really how we should view it. Not “is the mouse there or not there?” But, rather, “is it getting better or worse over time?” And Pascaline noted that the science backs up that outlook. One of mouse’s molecules “metabolizes over time into a form which is considered to be 100 times harder to detect” (and thereby imperceptible to pretty much everyone). Simply keeping the wines for longer, especially in bottle, might do the trick.

But here’s the thing. All mouse, all the time isn’t our predetermined destiny. As Lee puts it, “many of the OG vignerons who once produced mousy cuvées here and there have better learned their craft and mastered their terroir, and no longer make wines with mouse.”

I think that “mastered their terroir” part is really important. Climate change isn’t going anywhere; higher grape pHs are going to be the norm. Yet really talented winemakers are learning how to combat mouse while still making natural wine. Sure, it might mean a bit of sulfur. But it also means things like picking earlier, fermenting hotter, topping up, colder cellars, longer elevage, releasing later, and keeping a closer eye on pretty much everything.

Every wine doesn’t have to taste mousy. But this thing that’s been bothering me isn’t likely to go away on its own. The world is warmer, grapes are reacting, yeast and bacteria are reacting, and wine is going to be fundamentally different. Mouse isn’t likely to be the last symptom of this that we see (e.g., the severe frost that looks to have hit many major wine regions in France last night and could wipe out entire vintages).

I’ve been pushing myself to make my own view of it more dynamic. More holistic. Sometimes in a world that’s hot as shit, great winemakers are going to make mousy wines. The evolution of those wines is more interesting and more vital than simply identifying them at this point. Mouse is a messy reminder that nothing we inhabit is static. And, honestly, while I hate mousy wine, that’s a beautiful thing.