Fermentation Troubles, Natural Fining, and Get Your Swirl On

What are the most common fermentation problems you encounter in your own cellar as well as in the “Wine Wizard” column?
Lauren Mowery
New York, New York

Hi Lauren, great question. There are so many steps along the way where a fermentation can get into trouble, or “go pear shaped” as my interns from New Zealand used to say. We could almost do a walk through from start to finish, or even picking to dryness and say well, it could go south on you at this point, here, here, and here . . . but then we might get discouraged and never make wine again.

For home winemakers, I think there are two common fermentation problems that tend to crop up the most: Proper yeast nutrition and fermentation temperature control. It’s relatively easy to measure the “big numbers” like Brix (sugar content/soluble solids by density) and even pH and total acidity. Those are all pretty inexpensive analyses to do for any home hobbyist who wants to do a little wet chemistry and play mad scientist in their own little home lab.

The harder analyses to do are those like amino acid analysis and nitrogen content for nutrition, for which commercial wineries or wine labs spend thousands of dollars on specialized lab equipment. A home winemaker either has to carry her juice sample (quickly!) to a chemistry-for-hire wine lab or they have to make a really, really good guess as to what the nutrient status of that juice or must is. When taking a stab in the dark, it’s probably advisable to add a little complex yeast nutrient (like “Superfood” or similar) in order to cover any missed bases. Taking this approach, a home winemaker runs the risk of over-feeding and subsequent residual nitrogen post dryness, which can continue to feed spoilage organisms later. Perfect, it ain’t. You can see why this is such a challenge.

Controlling fermentation temperature, so important to yeast health during fermentation (too hot and they get cranky, too cold they slow down) and wine quality (too hot and delicate aromas get blown off), is another tough thing for micro-producers to manage. Commercial wineries with big stainless steel fermentation tanks rely on circulating glycol systems and cooling jackets or big refrigerated rooms for barrel storage. It’s difficult, not to mention expensive, to have any kind of cooling system on a small scale. Add to this the fact that barrel fermentations notoriously get too hot (wood is a good insulator) and cause stressed-out yeast to excrete stinky hydrogen sulfide off-aromas and you can appreciate how fiddly it is.

Some home winemakers cool down must ferments by freezing gallon water jugs and tossing them (closed tightly) into fermenting totes, bins or trash cans of must during a punchdown. They then simply remove the jugs before the must gets too cold. If your nighttime temperatures are cold enough during harvest (or if you use frozen must) you could take advantage by rolling out your fermenting barrels or containers for a chill on the back porch. I recommend placing your fermenters on a cart with lockable wheels or even on a pallet, which you could then pallet-jack around carefully. Heating is a tad bit easier; many of us have warmed up the odd barrel or carboy with a heating pad or heating blanket. For small stainless steel tanks I’ve even taken a space heater and blown warm air on the surface for a while. The key is that for any of these above strategies you really have to monitor the temperature  of your fermentation in order not to arrest or over-accelerate  a fermentation.

In the “Wine Wizard” column, I really get a variety of inquiries. Many are of the “Oh no, I think I added too much of X” (usually acid or sulfur dioxide) type. Others are what I’ll call the “mystery goo” category where I’ll be asked to do my best to diagnose a strange ring, growth, film or mold on someone’s carboy or barrel. Another category of questions is what I’ll call the “life stage of a wine” question where someone will ask how long they should age their wine in a barrel, or when they should rack their particular kind of wine. As with all “Wine Wizard” questions, it really helps me if the question is as descriptive as possible to the situation: What kind of wine are you making, any initial chemistry if you know it (Brix, pH, TA, etc.) and any strange circumstances leading up to your problem. Of course, if any of you home winemakers run into any of these problems, or have other questions, send them (and a picture of the problem if you can) to me at
[email protected]. Happy fermenting!

How can you tell when one of your “white powders” (SO2, acid, etc.) is expired? And I also have a related question: When should you change out the solution in your
fermentation locks?
Holly Heggill
Sacramento, California

Of course the best thing you can do is check expiration dates on packages, boxes and vials. If you buy bulk loose powders (like tartaric acid in baggies from a larger sack) from your home winemaking or homebrewing supply store, be sure to ask the store owners when they opened the larger batches from which they re-packaged your smaller doses.

As a general guideline, things that have microbes as ingredients (yeast, malolactic freeze dried culture) pretty much need to be used within two to three weeks of opening. Powders that have lots of “delicate” ingredients like dry packaged complex yeast nutrients are really only good for about six months after opening. I find that inert dry acids like tartaric, malic and citric are pretty bombproof. I’ve had opened bags for over a year that have still been good. What seem to me to be the most unstable, apart from microbes, are liquid suspensions like liquid tannins, oak products, or fining agents. Usually these need to be used within a few weeks of receiving them, and certainly within a week or two of opening them. When in doubt, check a supplier’s website and don’t hesitate to contact the manufacturer.

As far as fermentation locks go, I tend to change the SO2 solution in my airlocks once every week or two. The sulfur dioxide will degrade over time and it’s nice to be sure that it is fresh and doing a good job of keeping down the microbes around the opening to your containers.

What’s the most natural way to fine white and rosé wines?
Gin Yang
Sacramento, California

Well, an old-timer winemaker I used to work with would say, “The most natural fining agent for any wine is time.” What he meant was that with time, solids fall out, proteins eventually coagulate and fall to the bottom of the aging vessel and tartrates reach an equilibrium so they aren’t in excess and big crystals will precipitate as well. The problem with this approach when referring to fresh whites and rosé wines is that with enough time for all these chemical reactions to occur, enough oxidation and aging might take place in the wine such that it would be well past the time that you would want to bottle it. Whites and rosé wines are typically bottled within 4–12 months of harvest and part of their verve, charm and freshness is lost with extended time in barrel, keg or carboy.

That all being said, the fining agent you choose will depend on your definition of “natural.” If you mean using naturally-occurring substances, then things like bentonite (a natural clay that pulls out proteins), potassium bitartrate seed crystals (help precipitate excess tartaric acid that might form crystals later in the bottle), egg whites (pulls out excess tannins) and even isinglass (a protein isolated from the swim bladders of fish), and carbon powder (can bleach color from oxidized wine) all qualify, as do many other things. It’s important to read up on the topic. Browse any supplier’s catalog and you’ll see what I mean. For a simple white fining, to get it “heat stable” (remove excess protein so it won’t form a haze) and “cold stable” (remove excess potential tartrate crystals) is a good simple two step process to employ.

However, if by “natural” you mean you “don’t want to add anything” then don’t. Sometimes lees stirring for a couple of months, about once every week, can impart mouthfeel, help move some of these “time” reactions along and can help a wine taste more finished. It’s all up to you!

While watching an interview with a winemaker, he noted that the bouquet would be opened by “counter clockwise” swirling. I had never heard anyone indicate in which direction I should swirl before this. What say you, Wizard? Also, any chance there would be a difference depending on southern/northern hemisphere?
Jack Kerr
Santa Fe, New Mexico

I say Toe-may-toe, you say toe-mah-toe . . . this sounds like a bizarre wine myth in the making that we should just quash right here. Though undoubtedly, swirling your wine glass does indeed liberate more of the volatile (a fancy word for “smell-able”) compounds in a wine and is an important part of any wine-evaluation session (dare I say ritual) there is no canonical pronunciation for which direction in which it might be better to swirl.

Perhaps the winemaker you mention above was right handed, as am I. I find that it’s natural for me to swirl my glass in a counter-clockwise direction, but it’s just because my natural chirality (handedness) makes it easier for me to do so in that direction. Lefties tend to find that they have an easier time swirling in a clockwise direction. Try swirling in a direction “against your hand” and you’ll see what I mean. Perhaps what the aforementioned winemaker meant was that it’s important simply to swirl, no matter what the direction? If not, I would posit that he or she need to be taken to task for promulgating false wine snobbisms.

There is one thing to be said, however, for swirling in the direction “of one’s hand.” If one were right-handed, one’s swirl might be a bit stronger from the counterclockwise (more comfortable) direction and you may liberate some additional aromas or at the very least will lessen the risk of wine spill-over.

This discussion sounds like a fun cocktail topic or a party discussion waiting to happen. Feel free to have the conversation as a point of curiosity among your friends, but please do tell them that a real live winemaker told you that it didn’t matter — or make the wine better or worse — if you swirl counterclockwise or clockwise.