Whether you love ‘em or you hate ‘em, one thing is true: When the weather creeps above 90 degrees, a hard seltzer is more refreshing than even the most sessionable IPA.
The brew day for a seltzer is deceivingly simple: Its only requirements are boiling a sugar syrup and preparing a neutral yeast strain to pitch. But getting a sparkling-clear, fully attenuated seltzer requires meticulous attention to detail, and as much effort as the most complicated homebrew recipes.
Four areas where hard seltzer brewing departs most from beer brewing are yeast management, clarifying, carbonation, and flavoring.
Feed the Yeast
Malt-based wort provides a nutrient and sugar-rich environment in which yeast fulfill their life’s purpose: fermentation. When making hard seltzer, the absence of malt means no nutrients are present (especially free amino nitrogen referred to as “FAN”) to help yeast strengthen their cell walls and prepare for the process of converting sugar to CO2 and alcohol. Without certain compounds, yeast won’t ferment at all; without others, they’ll perform a slow, and stinky, fermentation with lots of sulfur aromas.
The best move is adding yeast nutrient three to five times during seltzer fermentation, depending on the level of yeast activity. For a five-gallon batch, add four grams of nutrient when yeast is first pitched; a second addition 48 hours later; and a third after 72 hours. Monitor fermentation activity; when bubbling in the airlock slows, add more nutrient until you’ve arrived at a final gravity of 1.000. This is a much higher dose than typically used in homebrewing — that is because these nutrient additions are providing all the FAN and vitamins yeast need, instead of only supplementing the levels in (malt-based) wort.
Fight Sulfuric Off-Flavors
When selecting a yeast nutrient, be sure that the ingredients include diammonium phosphate. Diammonium phosphate provides FAN and specifically combats the creation of sulfuric off-flavors that are common when fermenting seltzer.
The other way to fight sulfur aromas in the final seltzer is to keep the fermentation as vigorous as possible. Bubbles of CO2 escaping from the fermenting syrup carry highly volatile sulfur compounds to the surface, and out of the seltzer. If the bubbles aren’t rising fast or often enough, sulfur compounds can remain stuck in the seltzer. Make sure to use yeast nutrient and even a second pitch of yeast if bubbles slow too much.
Be patient! It can take up to three weeks to complete fermentation on a seltzer because the yeast are in a hostile and nutrient-poor environment.
How to Get it Seltzer-Clear
One aspect of alcoholic seltzer that enhances how refreshing and thirst quenching it feels is its sparkling clarity. On a professional scale, this would be achieved by running the seltzer through a very fine filter. When brewing seltzer at home, there are a few things to do that help achieve that pure water appearance without expensive equipment.
Once fermentation is complete (the gravity of the seltzer is 1.000 or less) cold crash the fermenter. This can mean putting the fermenter in a refrigerator, moving it to a garage or other uninsulated area when the weather is cold, or any other available means to cool the fermenter quickly. Ideally the temperature would get down to 40 degrees, or even lower, without freezing any of the water in the seltzer. This cooling slows yeast activity and causes the cells to drop out of solution, flocculating to the bottom of the fermenter.
After being held at a cooler temperature for about three days, the seltzer is ready for fining. Using a fining agent like gelatin or isinglass at the end of fermentation is one of the steps to getting the seltzer crystal clear. When hydrated gelatin is added to the seltzer, it pulls particulate and yeast out of solution as it solidifies on the bottom of the fermenter. The correct ratio for clarifying is 1.2 grams of unflavored food-grade gelatin per gallon of seltzer.
Capture the Fizz: Force Carbonation
The hard seltzers on the market get their signature fizz from force carbonation. Kegging and force carbonating are also your best bet with hard seltzer made at home. Yeast already struggle to ferment the stuff, so hoping yeast can re-ferment in the bottle and naturally create that high level of carbonation (a process known as bottle conditioning) is likely to end in disappointment.
Transferring the seltzer off the gelatin and yeast cake at the bottom of the fermenter to a keg and force carbonating it to 2.9-3.1 volumes of CO2 will give you the most authentic, Claw-like, if you will, experience. The Brewers Association has a handy chart on page 89 of the Draught Beer Quality Manual for determining what level to set the CO2 regulator to achieve desired carbonation.
Fruit Flavors, Explained
To get the purest, most authentic fruit flavor, brewers opt for whole peeled fruit or fruit purees… usually. For the most seltzer-like seltzer, the drink needs to maintain its clarity while packing a mouthful of flavor. Many recipes opt for extracts — I’ve found these to have a slightly metallic, sometimes oily flavor. In beer, there are flavors from the malt and aromas from yeast to mask some of these less-than-ideal extract side effects, but with seltzer all you have is carbonation to complement your flavor. That’s why flavoring made specifically for sparkling water really shines as a way to add pizzazz to a homemade hard seltzer.
The flavor drops by SodaStream are formulated to keep the beverage clear and come in many of the standard seltzer flavors like mango, lime, and grapefruit. For a totally natural way to add fruity notes, True Citrus makes powdered, all-natural lime, lemon, and grapefruit packets. Both options dissolve readily in water-based solutions such as seltzer without adding any color.
Flavor drops, powders, or crystals should be added after the seltzer is fully carbonated. This helps the flavor stay in the seltzer instead of being blown off by CO2. Add a little flavor at a time, especially when using the SodaStream drops, and taste as you go. Too much of these flavor additives can quickly give the seltzer an artificial or cloying taste.