As brewing becomes increasingly competitive, with consumers demanding higher quality beers, and retailers looking for products with greater assurance of shelf-lives, this sector of the food and beverage industry is moving at a faster pace than ever. The biggest threat to beer quality is microbial spoilage. If beer is to survive for more than a few days once packaged, then attention must be paid to controlling unwanted microbial contamination.
With energy and water rates on the rise, as well as the increasing price of hops – it’s important that the risk of beer spoilage is minimised. In response to these pressures, modern brewers are increasingly focused on quality assurance throughout their process and actively integrating process innovations to maximise their productivity and the quality of the beer.
As beer is acidic, contains alcohol, is anaerobic, and contains hop preservatives, it is an unfavourable environment for most microorganisms. Despite this, it is nutritionally rich, and certain species of microorganisms love it! These are three of the most common:
Lactobacillus is one of the most common beer spoilage bacterial species. It is highly resistant to hop compounds and survives a higher thermal treatment than other lactic acid bacteria. It causes a sour taste, a silky turbidity as well as super-attenuation, which leads to over-carbonation.
This strain of bacteria is generally resistant to hop compounds and common sanitisers are not totally effective in removing it. It also tolerates changes in pH and ethanol concentrations during fermentation, and forms exopolysaccharides (β-glucans), increasing the viscosity of its host beer.
In a beer, this manifests itself as haze, increased acidity, high diacetyl (buttery) flavour, and the strand-forming β-glucans leading to a ropy consistency.
This is a yeast associated with production of highly volatile phenolic compounds, 4-ethylguaiacol and 4-ethylphenol. It also facilitates acetate production in the presence of oxygen.
A beer which has been spoiled by brettanomyces bruxellensis (brett) typically has a sweaty/smokey aroma and can be described as having an off-flavour. Brett also super-attenuates beer, causing over carbonation.
This yeast is able to ferment dextrins and starch, with a spoilage mechanism of decarboxylation of p-coumaric acid and ferulic acid to 4-vinylphenol and 4-vinylguaicol.
The effects of its spoilage can display themselves as ester/phenolic off-flavours, a medicinal or spicy aroma, hazy/sedimented beer, and super-attenuation, which causes over-carbonation.
Following good hygienic practices and using long maturation times have been common tactics for minimising beer contamination for many years. However, relying on these methods alone is risky as they depend on operator effectiveness. Nowadays, more modern approaches such as flash pasteurisation and sterile filtration using innovative filters such as BEVPOR BR are being employed by many breweries.
Sterile filtration refers to the microfiltration of beer to remove any spoilage microorganisms before it is packaged. This is a reliable technique to eliminate contaminating microbes from beer, which in turn ensures a good shelf-life, retains the beer’s essential characteristics and significantly reduce costs.
To learn more about the benefits of sterile filtration for increased microbial security and cost reduction, download our white paper.
This post was contributed by Daniel Vecsey, market development manager, Parker Bioscience Division, United Kingdom.
Parker Bioscience Division offers filtration solutions to protect the quality and taste of beverage products. By working with our application experts, manufacturers can develop a tailored solution to ensure their beverage is free from contamination, full of flavour and visibly clear.