Alcohol content of fermented 'soft drinks' revealed

A Department of Health investigation has found that “a significant number” of fermented soft drinks contain alcohol over and above permitted levels, highlighting issues with unintended re-fermentation in the brewing industry.

The survey sampled fermented beverage products across Victoria, Queensland, New South Wales and Tasmania.

According to Food Standards Australia New Zealand, a fermented soft drink should contain less than 1.15% abv.

But the Department’s investigation found that 22.9 per cent of the samples of fermented drink kombucha had alcohol content higher than 1.15% abv, while 36.7 per cent of kefir samples, a fermented water-based drink made from kefir grain, were over the limit.

For other fermented beverages, including ginger beer and kvass, this percentage was 9.8 per cent over the 1.15% abv limit.

The agency said that it raised public health concerns, particularly for pregnant women, drivers and workers requiring a zero blood alcohol limit and those either living in dry communities or using prescription medication with which alcohol might interfere.

The number of non-compliant products led the Department to bring in government and industry stakeholders to discuss the issue, and it has once again put the spotlight on re-fermentation issues with both alcoholic and non alcoholic drinks.


Changing alcohol content due to re-fermentation is becoming an increasingly prevalent issue, as fermented soft drinks like kombucha, lower or alcohol-free beverages and fruit-flavoured beers grow in popularity as people look for healthier or more interesting alternatives.

Late last week, Brisbane’s Aether Brewing was forced to recall its gluten-free Ginger Beer’d after re-fermentation issues meant that its alcohol content could be greater than that stipulated on the label.

The Food Standards agency said that cans were at risk of explosion due to the pressure caused by ‘excessive’ carbonation in the re-fermentation process.

Getting on the front foot with the recall, head brewer at Aether Dave Ward said in a blog post that they were “heartbroken” about the re-fermentation issues and promised a full refund for customers who brought back the products.

He suggested that the ginger beer had been contaminated by wild yeast working with residual sugars, which are used to contrast the ginger.

“We’re still waiting on lab results,” he told Brews News, “but that’s what it appears to be. It’s unusual for ginger beer to behave that way, it’s usually treated like every other beer. We don’t back-sweeten, but we do use a non-fermentable sweetener.

“We’re working with some winemakers to discuss the use of possibly adding some sulphites, but we’re hesitant to do that and use preservatives when we’ve tried hard to be all natural.

“While [brewing all naturally] is brilliant in theory, it comes at the cost of potential issues such as the one that this batch is experiencing, that impacts the product’s stability and shelf life,” he continued in the blog post.

Standard fermentation process. Re-fermentation issues can occur at this stage due to cross contamination of yeast strains.

Ward said he and the Aether team were dedicated to “high-quality, continuous improvement”, and there are plans in the works to get a microlab on-site up and running to allow greater control over quality.

Pasteurisation equipment is also Aether’s shopping list, though it’s more a long-term goal due to the expense of the machinery, Ward said.

Solutions to re-fermentation issues

Aether is not the first to fall foul of re-fermentation problems. In February Beerfarmpulled its Pineapple Berliner Weisse kegs, while Rocky Ridge called back cans of the fourth instalment of its Rock Juice NEIPA after detecting carbonation defects. In late 2018 Newstead Brewing Co was forced torecall its Johnno Apple Cider product due to similar re-fermentation issues, while Kaiju! also experienced issues with its Golden Axe Cider earlier this year.

Steve ‘Hendo’ Henderson, of brewing consulting business Rockstar Brewer said that brewers he works with, which primarily brew alcoholic beverages rather than soft drinks, can find their re-fermentation problems rooted in one of three issues.

“The three most common ways for re-fermentation to occur are dry hop creep; the presence of Diastaticus, a variant of Saccharomyces yeast which secretes an enzyme which in turn breaks down non-fermentable sugars into fermentable ones; or the presence of residual sugars from things like fruit which are added in.”

He said that the solution for each of these problems was dependant on the issue.

“If you’ve got something that has residual sugars in it, and you want to keep those sugars in the product without the re-fermentation, then you either need to pasteurise, or you need to use sulphites, which inhibit yeast growth. They put the yeast to sleep effectively. You see it a lot in cider and alcoholic ginger beer.”

Non-alcoholic beer brewer Sobah dealt with re-fermentation issues through pasteurisation, but this may not be an option for brewers or other drinks manufacturers due to its effect on flavour and mouthfeel, Henderson said.

“When you pasteurise you’ll do some damage to the flavour of the product, but some brewers don’t mind taking that in return for increased shelf life and stability.”

Another issue – dry hop creep – sees enzymes in dry hops act upon starches and dextrins, breaking them down into fermentable sugars that are then involved with secondary fermentation with the remaining yeast. Additional alcohol and CO2 are then produced as natural (and normally desired) by-products of fermentation.

“Dry hop creep can also be resolved through pasteurisation, although that’s expensive to implement and there are a half a dozen different ways to deal with it. The main one is to dry hop your beer when it’s still fermenting, during your diacetyl rest.”

The last is the presence of Diastaticus yeast, which Hendo says is an interesting one because this yeast strain is commonly found in certain beers, such as a saison.

“Quite often in a brewery they will run a house yeast strain and then a special one. If there’s cross contamination of microorganisms it can cause re-fermentation. It’s pretty rare because brewers clean tanks well, but it’s still a risk.

“[The solution is] cleaning and also you can test for the presence of Diastaticus, using a PCR (polymerase chain reaction), a piece of equipment that looks for the DNA fingerprint of Diastaticus. Most brewers won’t have a lab in-house, but they can use a third party lab for testing.”

This is not the last time we’ll see a re-fermentation issue, according to Henderson.

“I think we’re going to see more of it before it gets better to be honest. A lot of it comes from a lack of skills around from brewers, understanding the process and also not knowing what to test for.

“A brewery needs to have a good quality system, in the form of a quality manual – a document every brewer should have that sets out what your company stands for in respect to quality, determines what is tested for and things like dealing with customer complaints and recall procedures.”

Additionally, the IBA launched a recall information pack earlier this year, outlining steps to take in the event of a recall. Prior to this, major retailer Endeavour made it a requirement that suppliers must have a food safety program and a food recall plan in place.

“What does a brewer do when they wind up in a situation where they need to do a recall? You can’t put your head in the sand, you’ve got to protect your brand. But that doesnt mean hiding the issue, it means being open and transparent,” explained Hendo.

“On the flip side, if you’re a brewery who tries to hide the fact something’s gone wrong or deny it, people will be savvy and that will do more to damage the brand than owning the recall and the message around it,” he concluded.

You can find the IBA’s recall information pack here.

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