Quality Control, Beyond Beer: Reducing Stress (and Sulfur) in Your Beverages

As brewers, we are used to dealing with sulfur, especially in our lagers. While a small amount can be desirable, nobody wants their nose near a tank that’s producing too much—let alone a finished beer that smells like rotten eggs.

However, as brewers increasingly go beyond beer, we’re learning that we also have to grapple with sulfur as an off-flavor in other beverages. Hard seltzers in particular—along with similarly produced flavored malt beverages (FMBs)—are extremely susceptible to sulfur during fermentation, with a risk of it lingering into the packaged product.

Here, I discuss ways to avoid stressing your yeast and, thus, avoid sulfur in your beer, seltzer, or other beverages.

[PAYWALL]

Sulfur in Beer

To better understand sulfur in seltzer, it helps to get some background on how and why it shows up in beer.

There are a few different ways that sulfur can present itself as an off-flavor. We often describe sulfur dioxide as having the aroma of a freshly struck match. When you’re brewing beer, this is normally only an issue with lager yeast.

However, the sulfur that occurs most prominently in hard seltzers and FMBs is usually in the form of hydrogen sulfide, which presents as rotten or hard-boiled eggs. While some pale lagers and German styles can have low levels of this and still be considered true to style, it doesn’t take much to get into the realm of unpleasant off-flavors.

To minimize it, yeast health is crucial. Temperature and nutrient conditions can cause an increase in concentration that can linger. The good news is that correct pitch rates of healthy yeast will almost always do the work, clearing the beer of sulfur before crashing. That may be counterintuitive, given that sulfur is a natural by-product of yeast metabolism and can’t be eliminated completely. Yet clearing it up quickly and efficiently—that is, reducing it below threshold—is vital to making a pleasant beverage.

So, how exactly do yeast clear up sulfur for us? Using a healthy pitch of yeast from the start gives the beer a fighting chance to clear up the sulfur that comes about midway through fermentation. However, patience also pays off: Part of the reason lagers get more time to condition is so that the yeast can complete their metabolism and eliminate these unwanted flavors.

This should all sound pretty similar to the occurrence and eradication of diacetyl—however, unfortunately, there isn’t a quick-and-easy sulfur version of the forced diacetyl test we use to check for precursors. (See “Dealing with Diacetyl,” beerandbrewing.com.) The best way to track how well the yeast are cleaning up sulfur is to smell the blow-off bucket during fermentation. That also leads back to sensory training and to having employees who are in tune with what’s considered to be true to brand. Finding an employee who is super-sensitive to sulfur can be a huge asset.

Sulfur in Seltzer

Because more craft breweries have been getting into hard seltzers and FMBs in recent years, some eggy drinks have been making the rounds. That’s because seltzer fermentations are more susceptible to sulfur that lingers on, unable to be cleared up by the yeast.

Compared to beer fermentations, seltzer fermentations are a more intense environment for yeast. A seltzer’s sugar base is less complex than a malty wort, leaving the yeast lacking in the nutrients they need for growth. Besides that, most hard seltzers experience an extreme pH drop during fermentation. While yeast favor slightly acidic conditions during growth, staying in an acidic environment is less desirable during the later steps of fermentation. After those early stages in a low-pH environment, the yeast often lack the energy needed to clean up sulfur.

Some producers get away with this by adding enough fruit and other flavorings that the sulfur isn’t easily detectable in the beverage—at first. However, aging and varying shelf-life conditions can cause that sulfur to push back to more evident levels.

The best way to ensure a fresh beverage over the course of its shelf life is to get your base as clean as possible in the first place.

Healthier Fermentation

So, what else can you do to help your yeast in that tough environment?

The crucial component is nutrients—but not just by adding more. The type of nutrients and the timing of the addition are what can give your yeast an upper hand.

Seltzer fermentations need diammonium phosphate (DAP). Luckily, many yeast suppliers sell nutrient packs specifically made for seltzer fermentations. It’s important to make sure that DAP is a component before adding them.

Overall, though, timing is the most important aspect of seltzer nutrition. When brewing beer, we tend to add most nutrients at the start of fermentation. But if we were to do that with seltzer, the yeast would get tired and burn out before they reach those crucial middle and later fermentation steps. That also applies to doing a nutrient dump midway during fermentation—the yeast might enjoy a little resurgence, but most of the cells will be pretty tired from living in that high-acid environment for so long.

When you’re making a seltzer or similar sugar-base drink, the best way to help your yeast at the start is to add nutrients incrementally over the course of the first few days after pitching. (This is what mead makers call staggered nutrient addition, or SNA—see “Mad for Mead, Part 2,” beerandbrewing.com.) It might take a little research, not to mention trial and error, to figure out what’s best for your yeast. Generally, however, doing at least three nutrient additions tends to be extremely helpful.

The first step should still be a nutrient dose when you pitch the yeast. This can be the largest volume of nutrients, or all doses can have the same volume. Then, typically, you’d add another at 24 hours and again at 48. Should you add a third time, at 72 hours? That will depend on your yeast strain and fermentation characteristics. In the end, an extra addition won’t hurt the fermentation—on the other hand, dialing in the doses can help to save money.

For many brewers, fermentations of hard seltzer or other drinks based on sugar washes are still new territory—and every new territory comes with its own learning curve. At the same time, many craft brewers are used to doing something extra to ensure a healthy fermentation, whether that’s for a high-gravity monster stout or a hard seltzer whose base is devoid of nutrients.

To avoid sulfur off-flavors, employing the right nutrients and staggering the dosage can give the yeast the extra push they need during those early stages of fermentation. Then they should have the energy they need in the later stages to clear up any unwanted sulfur that might linger in the base.

In turn, that leads to better quality over the shelf life of the brand and to improved consistency across batches.