Came across this Beer and Brewing article that came out this weekAspergillus oryzae, known in English as koji (Japanese: ニホンコウジカビ Hepburn: nihon koji kabi), is a filamentous fungus (a mold) used in Japan to ferment soybeans for making soy sauce and fermented bean paste (including miso), and also to saccharify rice, other grains, and potatoes in the making of alcoholic beverages such as sake and shōchū.
Might be giving this a try here in early JulyHowever, when you add koji into the mash of, say, a Berliner weisse, it will dramatically cut the time needed to properly kettle sour a beer.
“You talk to so many brewers who pitch lactobacillus (sometimes yogurt) on Friday, let it grow all weekend, producing lactic acid, and then come back on Monday to boil the wort,” says Bellomy. “With test brews that we’ve done with white koji, if you make it 20 to 25 percent of your grain bill, you could make a sour beer in a standard 1-hour mash time.”
It’s like the Fotomats of old: Sour in an Hour.
“White koji already contains the citric, lactic, and succinic acids, which impart a beautifully clean acidity to the beer,” Bellomy says.