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AEB Fermo Brew Acid – 500g

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FERMO BREW Acid is a yeast that produces a consistent and controllable sour beer via fermentation without having to introduce souring bacteria cultures into your cellar and is compatible with any conventional brewing yeasts to co-ferment and finish the fermentation to dry.

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A natural lachancea thermotolerance yeast strain that produces lactic acid while conducting alcoholic fermentation, in a novel, easy-to-reproduce process for any sour beer in the so-called “primary souring” process. This technique allows the brewers to avoid the use of lactic acid bacteria and kettle souring, shortening the processing time and costs while preserving the desired flavor complexity

FERMO BREW Acid is an indigenous wild yeast belonging to Lachancea thermotolerans sp. that produces a high concentration of lactic acid while initiating alcoholic fermentation. It has been selected for its fermentation performance, intrinsic acidification of the media through lactic acid production and its desired aroma and organoleptic characteristics typical of great sour beers.  The yeast is pitched on its own at the start of fermentation with the co-fermenting conventional yeast added to deactivate the FERMO BREW Acid after the desired drop in pH.  The pH will drop to 3.8 – 3.2 in 48hr – 72hr, depending on wort characteristics and fermentation temperature. FERMO BREW Acid exhibits clean but differing aroma profiles depending on the fermentation temperature; citrus fruits at cooler temperatures, tropical fruits at higher temperatures, and can be paired with Ale, Lager, Saison and even Brett yeasts.

Souring of beer is traditionally achieved by a bacterial inoculation/fermentation followed by long term aging, often in barrels. This protocol has several limitations, primarily long production times, risk of cross-contamination to other beers in the cellar and lack of brewer control over the terminal pH and organoleptic qualities.  As a result, Kettle souring has become a common alternative to traditional souring protocols and involves acidification by LAB inoculation in the kettle, resting at room temperatures for 24-48 hours and followed by another boil to kill off the bacteria. This method has been criticized to yield “one-dimensional” beers that lack the depth and complexity of traditional sours due to the loss of volatile aroma compounds caused by the secondary boil.  Also, it can hold up the brewing schedule, as the kettle can’t be used for production of new wort while the beer is souring. The use of FERMO BREW Acid to naturally acidify and initiate the fermentation on the cold side without the addition of bacteria represents an interesting and very reproducible alternative for your sour beer program.

Pitching recommendations: 25-50 g/hL at 11-25°C.



“The yeast definitely out-performed my expectations on the first two brews we used it in. I may be a bit of a dinosaur, but I have always been more of a live-lacto-sour kind of guy. I don’t really care for kettle sours so I have always just pitched lacto directly to fermentor and brought in 3rd party packagers to get it into cans, so when we decided to try this product, I was pretty skeptical of the character it would produce. As you can see by the order history, I have been pleasantly surprised by it. The pink guava sour it is used in has been a pretty decent seller and I am actually drinking quite a bit of it myself.”

Chris Derpak – Twin Sails Brewing


Weight1.2 lbs
Dimensions4.25 × 2.5 × 5.5 in

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