Episode #211: Heat and Cold Stability in Winemaking
Podcast: Inside Winemaking
Host: Jim Duane
Guest: Leigh Meyering
Recorded: January 16, 2026

Jim Duane:
Leigh, I’m really happy to have you back on the podcast. Since this is a standalone episode, I don’t want you to go through your full backstory. I’ll link your previous episodes for anyone who wants to dig deeper. But for listeners who may not have heard those, can you briefly explain what you’ve built with MyEnologist and what it is today? Then we’ll jump right into our focus on heat and cold stability.

Leigh Meyering:
Sure. MyEnologist is a winemaking consulting, analysis, and supply business. We have locations in Napa and Windsor, and we service everyone from home winemakers all the way up to large, industrial-sized wineries. We do wine analysis, and we sell many of the supplies wineries use: cleaning supplies, fermentation supplies, lab supplies, and a wide range of winemaking materials.

I’m also a consulting winemaker. I make wine for some small labels that don’t need a full-time winemaker, and I do ad hoc consulting. If someone has a question or concern about their wine, they can bring it in, we can taste it together, and talk through the issue. We can also set up trials to improve the wine and charge for my time.

One thing I really like about the wine analysis side of MyEnologist is the full-panel approach.

Jim Duane:
Can you describe what’s measured in your juice and wine panels? We don’t need to worry about fermentation panels for now.

Leigh Meyering:
Sure. Our juice panel is pretty similar to the other large labs here in Napa. You get the basics: Brix, sugar, acids, tartaric, malic, potassium, and nitrogen numbers like alpha amino nitrogen and ammonia. You also get TA and pH.

Our wine panel is more complete than most, because I’m a winemaker and I think it’s important to look at all these numbers regularly. The wine panel includes free and total sulfur dioxide, TA, pH, malic, lactic, glucose, fructose, acetic acid or VA, ethanol, and lactic acid. Lactic is one that many panels don’t include, but I do because if you ever see lactic climbing after malolactic fermentation is finished, that can be a sign of spoilage.

We use a FOSS Winescan, so we can get all of these numbers efficiently. My philosophy is that more information is better. Rather than selling each number individually, we sell the full panel. You send in 50 mL of wine and get a lot of data back.

Jim Duane:
At some point you added modules for stability testing. What other testing do you currently offer?

Leigh Meyering:
We do heat and cold stability testing, and we also analyze for Brettanomyces using a PCR-based test. That’s one of the main spoilage yeasts we look for.

We also do bench fining trials, which are essentially multiple heat stability tests with an added fining step. We’ll talk more about that when we get into stability testing.

Beyond that, we do some primary analysis to back up Winescan data. We’ll run enzymatic tests if needed, and occasionally we measure free SO₂ in juice. That’s not part of a normal juice panel, but sometimes a client wants it.

For example, I had a client whose fermentation wouldn’t start. We checked free SO₂ in the juice, and it was at the top of the measurable range. That explained the problem immediately.

Jim Duane:
Is there any analysis you’re hoping to add in the future?

Leigh Meyering:
Yes. I’ve been doing development work on tannins, phenolics, and color. Right now, those analyses are expensive, so most people don’t measure them. An HPLC analysis can easily be over $100.

I’ve been experimenting for the last few harvests to figure out which parameters are actually useful and predictive. Every method has its own scale, so you can’t always compare one method directly to another. I’m especially interested in understanding ripening in the vineyard in terms of tannin and color.

Because I have a lab and also make wine, I can pull daily samples during fermentation and see how cap management affects these parameters. I have a lot of data now, and the challenge is figuring out what it all means. Eventually, I hope we can offer this analysis at a reasonable cost so clients can get it alongside a regular wine panel.

Jim Duane:
Let’s talk about stability. Who doesn’t need to worry about heat and cold stability?

Leigh Meyering:
The best way to answer that is to talk about why stability matters. Stability tells us how much a wine is going to change over time and under certain conditions.

If you’re a large winery shipping wine across the country, your wine will experience temperature swings. Or if someone throws a case of wine in their car trunk during summer, it can get very hot. Those temperature changes can affect physical stability.

Cold instability shows up as tartrate crystals. Tartaric acid is less soluble at cold temperatures, so it can precipitate out as crystals. They’re harmless, but many consumers think they’re glass.

Heat instability is about proteins. When wine gets warm, unstable proteins can denature and create haze or cloudiness.

If you’re a home winemaker and your wine stays in your cellar, and you don’t mind decanting off tartrate crystals, it may not matter. But if you’re selling wine and worried about returns, stability becomes much more important.

Jim Duane:
What about red wines? How concerned should people be?

Leigh Meyering:
Heat stability is usually not a big concern for reds, because you can’t see haze in most red wines. Also, tannins bind proteins, so many proteins drop out naturally before bottling.

Cold stability can matter more, depending on the site. For example, Spring Mountain wines often have high tartaric acid, so tartrate crystals are common. Most consumers expect some sediment in red wines, so it’s usually not a big issue.

For whites and rosés, it’s different. You can see haze and crystals easily, and consumers tend to react badly to that.

Jim Duane:
So let’s focus on whites and rosés. When you’re preparing a wine for bottling, how do you organize your approach to heat and cold stability?

Leigh Meyering:
I actually start thinking about stability at harvest. During juice settling for whites and rosés, I usually add bentonite. You can add a lot of bentonite at the juice phase without stripping aromatics, because there are so many precursors present.

This also helps with juice settling. If you know a varietal is always protein unstable, like Sauvignon Blanc or Pinot Grigio, you can add more bentonite up front. We’re talking about five pounds per 1,000 gallons, sometimes even more.

Later on, you may only need a small fine-tuning adjustment. This avoids having to add a lot of bentonite later, when people worry about stripping the wine.

Jim Duane:
Do you see reductions in nitrogen from those juice-phase additions?

Leigh Meyering:
No, not really.

Jim Duane:
Any cautions?

Leigh Meyering:
If you can’t cold settle and rack cleanly, you may want to be more conservative. Bentonite is heavy and settles quickly, but if you’re constantly stirring it back up during fermentation, that’s not ideal.

Jim Duane:
Let’s jump ahead to January, when people are finishing wines. What’s critical at that stage?

Leigh Meyering:
The most important thing is that your stability testing reflects the wine you actually plan to bottle. Two stable wines blended together are not automatically stable. Any additions—sweetening, concentrates, blending—need to be represented in the test sample.

Jim Duane:
How do you decide which cold stability test to run?

Leigh Meyering:
That depends on how you plan to stabilize the wine. If you’re doing traditional chilling and seeding, the Davis conductivity test works well.

If you plan to use products like carboxymethyl cellulose, or CMC products such as CelStab, then protein stability matters, because CMC can interact with proteins.

Mannoproteins are different. They can be used on protein-unstable wines, but they can make heat stability worse and are less effective at cold stabilization.

Traditional chilling and seeding is energy-intensive and expensive. You’re holding wine at around 30°F for weeks. Many wineries and home winemakers can’t or won’t do that anymore.

CMC products are easy to use, effective, and don’t change TA or pH. In my experience, CelStab has no sensory impact on wine.

Jim Duane:
Can you walk through the cold stability tests you offer?

Leigh Meyering:
We offer three: the Davis conductivity test, the DIT test, and the ISTC 50.

The Davis conductivity test answers the basic question: is your wine cold stable or not? It’s fast and effective.

The DIT test is more extreme. It’s run colder and longer, and it’s meant to approximate near-infinite stability. It’s useful for high-risk shipping situations, but it’s often overkill.

The ISTC 50 is used after you’ve done something to stabilize the wine. It confirms whether your treatment worked.

Jim Duane:
Anything else people should know about cold stability?

Leigh Meyering:
Sampling is critical. Don’t chill your sample before sending it in. Don’t leave it in a hot car. And if you’re back-sweetening, do that on the bench before testing.

For sparkling wine that hasn’t gone through second fermentation, you need to account for the additional ethanol that will be produced later.

Jim Duane:
Let’s move to heat stability.

Leigh Meyering:
Heat instability shows up as haze or a snow-globe effect in white wines. It’s unattractive, especially in clear glass bottles. Fortunately, it’s easy to fix with bentonite.

We run a heat denaturation test: filter the wine, heat it at 80°C for two hours, cool it, then measure turbidity. If turbidity increases, proteins have come out of solution.

Jim Duane:
On your form, people see options for a heat stability check and a bentonite trial. What’s the difference?

Leigh Meyering:
A heat stability check tells you whether the wine is stable. A bentonite trial tells you how much bentonite you need to add to make it stable.

We usually run trials at 0, 1, 2, 3, and 4 pounds per 1,000 gallons, always with a control. The control is essential to make sure the test is valid.

We can customize levels based on what the winemaker is comfortable adding. After the trial, we filter the samples and run heat stability tests on each one.

Jim Duane:
How do people interpret the results?

Leigh Meyering:
Typically, a turbidity change of less than one to two NTU is considered stable. But it’s subjective. It depends on your risk tolerance and philosophy.

I always recommend tasting the trial samples. Bentonite doesn’t always strip wine. Sometimes it actually cleans it up and improves aroma and texture.

Jim Duane:
Any quirks you see in trials?

Leigh Meyering:
With rosé, sometimes the results are wonky. Turbidity might drop, then rise, then drop again. We think that’s related to colloidal or color instability. If that happens, call us. It’s not unheard of.

Jim Duane:
Let’s talk bentonite prep.

Leigh Meyering:
Preparation is critical. Bentonite must be properly hydrated and allowed to swell, following the manufacturer’s instructions. If it’s not prepared correctly, it won’t work as expected.

Different bentonites have different requirements. Some need hot water, some cold. Some need more time than others. Always follow the directions.

We can run trials with the bentonite you plan to use, as long as you provide it and tell us how to prepare it.

Jim Duane:
What order do you prefer when doing stabilization work?

Leigh Meyering:
Ideally, I do heat stabilization first with bentonite, then cold stabilization. If you’re using CMC, that’s added after filtration, right before bottling.

Plan ahead. Don’t wait until the week before bottling to think about stability. And if you make changes, retest. It’s not expensive, and it can save you a lot of trouble.

Jim Duane:
Any final advice?

Leigh Meyering:
If you haven’t racked barrels yet, pull a truly representative sample. Barrel variation matters.

Pull samples from clear wine, not from lees. Protect samples from extreme temperatures. And if you’re using CMC, always confirm heat stability first.

Jim Duane:
Leigh, this has been great. Can you share contact information for MyEnologist?

Leigh Meyering:
Everything is on our website at www.myonologist.com. There’s a PDF form you need to fill out when sending samples. It explains all the tests, volumes required, and costs.

Our phone number is 707-812-1242. My email is leigh@myonologist.com. You can also visit us in Napa or Windsor.

Jim Duane:
Thanks so much, Leigh. This was fantastic.

Leigh Meyering:
Happy to be here.