During a period of time last year Left Hand Brewing Co. received complaints from customers and accounts of off-flavored beers, exploding bottles, and other quality control issues. The brewery, based in Longmont, Colorado and the makers of the popular Milk Stout Nitro issued a recall for that beer and several others, brewery officials said in a statement, destroying or removing $2 million of product from the market. It then launched an investigation into the cause of the contamination.

The brewery, in its lawsuit filed last week in Boulder County, Colorado accuses White Labs, the major yeast supplier with selling “contaminated and defective yeast in 2016 which contained Diastaticus.”

The yeast in question is WLP090, also known as San Diego Super Yeast.

Despite White Labs’ Certificate of Quality Assurance guarantee, Left Hand found, through a wide-ranging investigation and multiple tests, "the source of the Diastaticus contamination was the yeast supplied by White Labs,” said Eric Wallace the brewery CEO in a statement. “The presence of Diastaticus caused the affected Left Hand beers to secondarily ferment, resulting in multiple defects.”

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The statement continues: “In order to protect its consumers and to assure the quality of its beers, Left Hand performed a withdrawal of all Milk Stout Nitro products and other beers which contained the contaminated yeast from the market, shut down their brewery for a period of time, destroyed packaged and in-process product, and incurred significant financial losses and damages.”

Wallace, in the statement said that Left Hand “promptly notified” White Labs of the problems with its yeast, but to this date White Labs has done nothing to address the issue. The lawsuit notes that Left Hand has since changed yeast providers.

This morning, responding to a question from Craft Beer and Brewing Magazine, White Labs spokeswoman Nickie Peña sent the following response:

“The case, which is being defended by our lawyers, claims that Left Hand Brewery received a batch of contaminated yeast from us in 2016. There is no specific proof on where the contamination originated from, as each White Labs culture undergoes a rigorous testing process from start to finish, which includes 61 quality checkpoints throughout the propagation cycle,” she wrote. “Additionally, every batch of yeast is tested to confirm it is contamination free prior to shipping. We cannot provide further comment due to the ongoing litigation.”

The other beers recalled by Left Hand were Extrovert IPA and Warrior Fresh Hop IPA. This included variety packs that featured the affected beers. Left Hand, in the lawsuit, says it shut down production for two weeks while it cleaned its entire system, replacing several “valves and pipe pathways” in order to clean any infection.

Following the re-starting of the brewery Left Hand says it again ordered yeast from White Labs, and conducted tests on the sample and found that it was again contaminated with Diastaticus. It then applied new filtering protocols on the beer to ensure that any Diastaticus was removed.

“It is unfortunate we had to file a lawsuit, but we didn’t have a choice. As an employee-owned brewery, the fate of our brand and employee livelihood was compromised and we are asking White Labs to take responsibility for the quality of their product and stand behind their guarantee,” said Wallace.

