Digging Into Seltzer Nutrients

The answer to this question requires an upfront disclaimer about any bias or product promotions that may accompany my answer. I work for BSG (Brewers Supply Group) and we carry several products used by producers of seltzers, and some of these products will be mentioned in this answer because they are most familiar to me. There are many other products available in the marketplace. I don’t do infomercials and want to get the disclosure out of the way up front. Now let me tell you about this great new product!

In all seriousness, there are really two paths that can be followed when it comes to the yeast + nutrient decision making for seltzer production. The easiest path is to select a yeast + nutrient product that has been specifically developed for seltzer production. Since the starting point of most seltzers is a sugar solution somewhere in the 8 °Plato (1.032) to 20 °Plato (1.083) range and the desired outcome from the base fermentation is pretty much the same regardless of what is done after fermentation, for example cleaning up the base, adding acids, and adding flavors, it follows that yeast + nutrient products provide a useful tool to the seltzer maker. Call me lazy, but these products are really attractive to me because someone has already figured out what combination of goodies works the best to optimize the product. The addition rates can be varied by sugar water density (can we just call this “swort” as in sugar wort?), and you can proportionally adjust based on the recommended use rate at a given “swort” density.

Many seltzer makers are happy with these products and are not bothered that the formulations are proprietary. The companies that produce and market these mixes have done the bench trials, invested into the formulations, and keep the information locked down. You want to know more so you can create your own yeast + nutrient blend. There is no silver bullet to this process and I will give you some basics to help you move in the right direction.

The first thing that needs to be addressed is the elephant in the room . . . as in, what’s the big deal with seltzer? After all, Saccharomyces cerevisiae (translated from Latin as sugar yeast from beer) seems like the right organism for the task of fermenting “swort.” But there is a pretty huge difference among the various sugar-containing solutions to make alcoholic beverages. Brewers have things pretty easy because wort contains much more than sugar and great beer can be made without ever having to worry about nutrients, aside from zinc, which really is one of those good-to-great things. OK peanut gallery, I am not talking really high-gravity beers and/or worts with high adjunct ratios, so pipe down!

Winemakers deal with fruit musts and must (no pun intended) be more mindful of nutrient levels. Then there are meadmakers . . . I have often wondered if the wide array of things added to honey must has not been in the pursuit of the perfect mead nutrient. Hmmm, if only the Pythons were still creating comedy this could make for an interesting sequel to Monty Python and the Holy Grail! And now we have swort for seltzer, with nothing at all for the yeast cells that are expected to transform this nutrient-empty liquid into a clean base to build upon. That’s why nutrients are needed.

This is a high-level, how-to discussion and the very deep topic of yeast nutrition will be kept brief. Yeast cells need nitrogen to grow because without nitrogen cellular functions simply don’t exist. This is because enzymes are proteins, and proteins are built from amino acids, and amino acids contain nitrogen. DNA and RNA also contain nitrogen. Like Bob Marley wailed, “no nitrogen, no wine.” Yeast also require phosphorous to multiply because phosphorous is a critical cell wall constituent, as in phospholipid membranes, required to synthesize DNA and RNA, and essential for the cellular fuel known as ATP (adenosine triphosphate). And don’t forget the vitamins, especially B-vitamins, enzyme co-factors like zinc and manganese, and minerals like calcium and magnesium that are essential for cellular activity. If this paragraph does not send you to the yeast + nutrient shelf, keep reading!

A great resource to help simplify this messy topic can be found on the BSG website at https://bsgcraft.com/resources/FAQ/4.26.18%20Nutrient%20Addition%20Charts.pdf. This is where that disclaimer comes into play. If you follow this link you will find an extremely useful chart that provides several nutrient addition approaches for fruit musts with varying levels of yeast assimilable nitrogen (YAN). Note that all of the addition rates in this table are pegged to 25 °Brix (essentially the same as 25 °Plato or 1.106 specific gravity) must and that there is a statement that reads “Lower Brix grapes need less nitrogen, higher Brix grapes need more.” This point was made earlier, and reinforces the importance of the question you raised about matching nutrients with ABV/swort density.

The very high-risk must category is a good basis for formulating a nutrient blend for seltzers because the risk levels in this table are defined by YAN concentration, and swort has zero YAN. Without calling out product names, the suggested strategy for all of the examples shown in the high-risk must category use a blend of a proprietary yeast food + diammonium phosphate (DAP). Almost all nutrient-rich yeast foods on the market contain a large percentage of lysed yeast cells as the primary source of vitamins and minerals. The DAP component brings simple nitrogen and phosphorous to the party, and a blend of these two general types of yeast foods give yeast a fighting chance to convert swort into something that is fit for consumption.

And that brings up yeast. You need it! The most popular strains being used by the DIY crowd fall into two main categories: 1) Brewing yeast known to be clean and alcohol-tolerant, such as the Chico strain of yeast, and 2) Wine yeasts known to be clean and alcohol-tolerant, especially so-called prise de mousse yeasts that are often used for sparkling wine production. This is where you will need to do bench trials to select the strain that tickles your funny bone.

If all goes well with your nutrient formulation and yeast strain selection, you will produce a relatively clean product from primary fermentation. Two common off-flavors encountered by seltzer makers are hydrogen sulfide (H₂S) and sulfur dioxide (SO₂). Sulfur dioxide smells like a burnt match and H₂S supposedly smells strongly of rotten egg— but how often do we encounter rotten eggs in our modern lives? In any case, you’ll know it when you smell it. These are followed by the perfume-like esters that many describe as sake-like. Although sake-like esters are not unpleasant, they are distracting in a hard seltzer. This is where the big mop called activated carbon comes in handy to clean things up before adding acids, flavor extracts, herbal tinctures, or fruit juices to your fermented base.

This answer really just scratches the surface of the topics raised in your question. If you are serious about this project, the most efficient route will be running dozens of 1-liter (1-qt.) bench trials and collecting as much data as possible. If this is more of a science project than you expected, consider checking out some of the yeast + nutrient blends on the market and finding the product that suits your particular needs.

Response by Ashton Lewis.