When Hawke’s Bay beverage company Parkers decided to get out of a short foray into the beer business they wanted to do something useful with a batch of leftover pilsner. The answer, after much trial and error, is a probiotic drink made with beer that’s been turned into vinegar.

Some readers may remember the brief life of Deco City beer, which Parkers brewed under contract. Well, that’s the beer that got turned into vinegar and is now an ingredient in Hop Pop, a trio of flavoured, kombucha-adjacent drinks.

Parkers got out of beer because of the flooded market and Covid, and managing director Doug Speedy asked the question “does this leftover beer have some value?”

Food engineer Jon Marks, a keen home brewer, knew that the ethanol in beer, with the application of acetobacter, could be turned into acetic acid as the base of a probiotic drink — a way of keeping in all the nutritional value of the beer while getting rid of the alcohol.

Humans have been producing vinegar for centuries, but Marks said it was still a learning curve to apply the process to beer.

“We were trying to encourage nice clean product, which means utilising the right bacteria and doing it in the right manner so we can get the taste we want and be able to repeat it,” Marks said.

One issue is that hops are naturally antimicrobial and the worry was that the beer could inhibit the work of the acetobacter.

Marks did numerous trials on 10-litre batches, controlling temperature, oxygen, pitch rates and different cultures.

Temperature turned out to be a crucial element as when it gets too warm off-flavours develop and if it’s too cool the process comes to a halt.

Acetobacter creates vinegar by processing ethanol, meaning the final acetic acid is alcohol-free.

Stevia was added for sweetness along with sparkling water and three flavours: blueberry, ginger & lemon, and strawberry & vanilla.

Unlike beer which cannot be marketed for its nutritional benefits, the vinegared beer suddenly becomes a healthy probiotic drink full of live cultures and vitamins.

Marks says it’s a variation on kombucha

“It’s kombucha-adjacent — kombucha is essentially a tea vinegar so it’s similar but different to kombucha.”

Parkers were able to get 4000 litres of vinegar from the original leftover beer and they are happy to let breweries know that they’re in the market for beer that might otherwise to waste.

“We need more feedstock. We have sufficient beer vinegar for the launch of this product and to replenish stock but after that, we need more fresh feedstock.”

They’ve done a few experiments with different beer styles and Marks found very hoppy beers created a “flavoursome beer vinegar” but the flavour was too intense to be used on its own and had to be blended with other vinegar.