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Canned drinks From February 2019

New validated method for challenge testing canned drinks

Our brewing services microbiology team at our Nutfield site has recently validated a new method for inoculating carbonated canned beverages and soft drinks. It has the benefit of allowing shelf life trials to be conducted in original packaging, under minimally altered environmental conditions.


Food safety is a major concern for everyone involved in the food and drink industry from producers to policy makers and retailers to consumers, and it is imperative that all precautions are taken to safeguard consumers’ health. Just because an organism is in a product, it does not mean that it poses a problem or will compromise product shelf–life. Most pathogens and spoilage organisms will need to survive and grow in order to reach levels at which the product is compromised.


Microbiological challenge testing


Microbiological challenge testing is the laboratory simulation of what can happen to a product during distribution and subsequent handling if it were to be contaminated with a microorganism. It involves deliberate inoculation of the product with these organisms, typically a specific pathogen or group of spoilage organisms, after which the product is stored and tested during shelf life.


When conducting microbiological challenge testing, thermal processing or stability studies, imitating the in-trade conditions a product will experience can be difficult. Beverages are mainly supplied in packaging that contains little oxygen, so it is important to maintain low oxygen concentration when conducting laboratory stability trials. Whilst this is achievable for most packaging types, trials with alcoholic beverages and soft drinks, which are packed in aluminium or tin-plated steel poptab cans, pose a challenge as they are not easily resealable following addition of the test organisms.


Until now the only way to conduct laboratory trials of canned (carbonated) beverages and soft drinks was by dispensing the test liquid into alternative containers. This leads to a significant reduction in carbonation and introduces oxygen, which can affect the results. Reduced carbonation and increased oxygen levels will favour microorganisms which normally would not be able to grow under anaerobic conditions. Additionally, strict (obligate) anaerobic bacteria are not able to grow in the presence of oxygen and, in some cases, these microorganisms would die.


Our new method deals with these issues. A small hole is drilled into the can under aseptic conditions and, following the microbial inoculation, sterilised rivets are used to reseal the ‘inoculation hole’. The rivet is able to withstand increased pressures that may occur during the growth of fermentative gas-producing organisms.


Our challenge testing methods cover all potential microorganisms that companies may wish to consider. Manufacturers also have the option to use our microbial growth prediction service, based on mathematical growth models. These predictive models are the quickest method, allowing cost effective testing of different ‘what if’ scenarios when reformulating or developing new products, to predict the levels of microbial growth.


Contact: Grzegorz Rachon
+44(0)1737 824298
grzegorz.rachon@campdenbri.co.uk