Have you ever been frustrated by over-carbonated beer?

You’ve followed the correct procedures and quality protocols right through the brewing process then packaged your beer only for it to gush out of bottles or cans on opening.

Whether on shelves in a warm outlet, or even worse, in a customer’s hand, gushing beer is embarrassing, hazardous and it can damage your brand and business but it could also be an indication of problems in your brewery’s microbiology.

It could be a sign of diastaticus.

gushing beer

Diastaticus is spoken about in hushed tones in brewing circles as if admitting to some embarrassing personal illness. This article is aimed at helping breweries who have suffered from this problem by answering two important questions, what is diastaticus and why is it suddenly appearing now?

What is diastaticus?

Put simply diastaticus is a yeast that produces glucoamylase enzymes which digest the dextrins in beer. This action releases sugars which then ferment in the bottle, can or keg producing excess carbon dioxide.

As we know, starch is digested in the mash to produce fermentable sugars and non-fermentable dextrins. Fermentable sugars are converted to ethanol and carbon dioxide in fermentation while dextrins remain inert to contribute to body and mouthfeel. As a rule, dextrins can be left safely in a cask or bottle conditioned beer because they are not fermented by brewing yeasts (Saccharomyces cerevisiae and S. pastorianus).

However, this is not universally true for other yeasts. In fact, most non-brewing or wild yeasts are able to produce enzymes that will digest larger sugars into fermentable ones. This causes problems as carbon dioxide builds to unsafe levels. Any contamination with these yeasts and your beer will gush.

Normally this phenomena would be limited to cask, bottle (or canned) conditioned beers as mass produced beer is often filtered and pasteurised removing any remaining yeast and therefore reduces this risk. However, there does remain the possibility that filtered or pasteurised beers could be infected with diastaticus during packaging in contaminated environments such as the filling area where yeast is introduced from the environment or nearby biofilm.

Gushing beer points to contamination with live yeast (although in some cases inert materials from malt may be the cause). A simple solution to diastaticus contamination is to maintain the highest hygiene standards in the production process particularly throughout fermentation and packaging.

Of course, a high standard of hygiene should be standard practice for any self-respecting brewery but there is also the added complication of the yeast stock itself being contaminated. That’s why a reliable yeast source is essential. Ideally one from a supplier with the expertise, facilities, and equipment to check for yeast purity.

Why is diastaticus suddenly appearing?

It’s important to understand that diastaticus yeast is its natural condition. The yeasts we use for brewing today are chosen because they have a mutation in the STA glucoamylase gene that renders it inactive. This mutation has happened over centuries of brewing and these mutated yeasts are used produce the standard beers we generally brew today.

However a recent scientific surveys of yeast genomes show that many wild and some brewing yeasts now carry an active STA gene.

The recent upsurge in the popularity of Saisons and sours has meant more and more breweries are now producing them. Saison and sour production requires diastaticus yeast with active STA genes and once they are introduced to your production environment the possibility of contamination into other beers increases. This is both worrying and reassuring. Worrying because the use of multiple yeast strains increases the risk of contamination but reassuring in that it points to the actions you can take to minimise this risk.

As previously stated, hygiene is paramount to prevent cross- contamination not only in local environmental cleanliness but also in the strict separation and management of yeast cultures from pitch to discard. For example, throwing a bucket of Saison yeast slurry into the central drain is sure to create an aerosol you don’t want to mix with your standard pitching. Segregating vessels and pipework for sole use by STA positive yeast is advisable as is double decontamination of any packaging system after use. Finally, ensure that your yeast is from a trusted and tested source and if you are at all unsure have it checked by a competent laboratory.

Reassurance is important in order to be confident of your product’s safety but testing for diastaticus is not that simple. Using starch or copper sulphate agar plates is one possible method but this will not guarantee that all negatives are true. Forcing tests will give a predictive indication of problems if samples are kept warm at around 30ºC but this does take time. The most reliable way to check for diasaticus contamination is by using molecular biology PCR techniques. These are quicker and more reliable because they are based on gene sequencing. However, they do require specialist equipment, expertise and laboratory skills. And that is where a trusted brewing partner like Brewlab comes in. With the right equipment and expertise, our range of specifically designed genome yeast tests will ensure that your brewery has a significantly reduced risk of diasaticus contamination.

Innovation in modern brewing techniques means that the risk of diastaticus contamination could be viewed as a price worth paying for diversifying your beer portfolio. But it can also lead to costly product recalls, reputational damage and could stop a growing business in its tracks. The risks are manageable and with the right support from a trusted laboratory they can be significantly reduced. One thing is for sure brewing is set to become more technical in the future.

To find out more about our diastaticus tests call +44 (0)191 516 6144 or email info@brewlab.co.uk

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