Our house yeast is Imperial Organic Yeast A38 Juice, and I love it for the ester profile. It has these esters of mango and a lot of citrus pith and zest—especially lime zest. When combined with the hops we like—Simcoe, Citra, Amarillo, Mosaic—it just vibes. And it really responds well to the conditions we put it under.
For brewing our regular IPAs, we whirlpool the collected wort to homogenize any salts or nutrients before cooling the wort into a fermentation tank. We pitch the A38 Juice yeast inline with this wort.
When the yeast gets going—our standard operating procedure is about 15 percent attenuation or 2° Plato down, and that’s usually less than 20 hours in—we hit the fermenting wort with the dry hops.
Most of the hops go into the fermenting wort, and then we spund the fermenting wort for 24 hours at one bar. (Spunding is a process often used by lager brewers to naturally carbonate their beer. A spunding valve attached to the tank carefully controls the release of carbon dioxide and keeps the tank pressurized.)
At this point, our pales ales and IPAs are about 40 percent through primary fermentation, so we close the spunding valve and allow the temperature to free rise a few degrees and build some pressure. The fermentation vessel is essentially closed a day into fermentation. We allow the beer to sit on the hops for about 5 days after closing the spunding valve before cooling the beer to packaging temperature.
By day 7, we smell the beer and check for anything off. If it’s okay, we crash on day 8. It takes about a full day to get the tanks cold, and then the beer hangs out. On day 12, we rack it out to the bright tank to package it. The beer comes out really fresh and fresh-tasting, too.
For hops, we use about 3.3 pounds per barrel, but the beers aren’t coming out super-grassy. I know a lot of brewers have an issue or struggle with green beer, and we did too. But we don’t anymore. I think that’s because we put the hops in contact with the yeast, which is going after everything. And making that yeast work under pressure for a few days does something to clean up that vegetal matter.
I know a lot of people use Conan or London III, but those yeasts seem better suited for letting fermentation do its thing and then hitting the beer with the hops. For us, A38 Juice works well with the hops and under pressure.
A38 Juice also plays well with other yeasts if we’re doing a blended fermentation with styles such as a sour IPA. We recently did a few sour IPAs in collaboration with WeldWerks and Parleaux Beer Lab. In that case, we followed our normal mashing process, collected the wort, and pasteurized it.
We then put it into our sour tank where we allowed the pH of the wort to drop and some of the fruit character of our house sour culture to build. We then transferred the soured wort back to the kettle and boiled it before cooling into ale fermentation.
A38 Juice was a reliable workhorse with these sour IPAs. At a very low pH, it still fermented those beers out as consistently as in a clean fermentation. Also, the character of our sour culture with the tropical esters from A38 Juice just really boosted the overall funk with these thick fruity, even plum-like, esters.