Challenge testing of canned drinks - Are yours microbiologically stable?
15 June 2022
Roy Betts, Fellow and Grzegorz Rachon, Brewing Microbiology Research Section Lead
Consumer demand is evolving and cans are proving popular thanks to their convenience and recyclability. The beverage
industry is responding to demand and packaging is subsequently changing to keep up with the fight to win market share in drinks categories.
Product formulation, processing, packaging technologies and transport expose canned drinks to microbiological risks.
With around 600 million, almost 1 in 10 people in the world, falling ill after consuming contaminated food and drink every year, understanding
if a product is microbiologically stable is critical for food processors and handlers.
How do I know if a canned drink is microbiologically stable?
With most canned drinks, knowledge of their stability is based on the experience of industry technologists, coupled
with information in scientific publications on procedures that eliminate or prevent the growth of organisms. However, for entirely new products
or formulations, this knowledge and data may not exist. While some predictive models may provide insight, these do not establish if the
canned drink is stable and will prohibit microbial growth.
Microbial challenge testing can solve this issue.
What is a challenge test?
A challenge test is used to simulate what happens to a product during processing, distribution, preparation and
handling, throughout its shelf-life, should it be contaminated with a microorganism. It is performed by deliberately inoculating a food or
drink with a microorganism of concern, a pathogen or spoilage organism, to determine if the organisms would present a potential health hazard
or spoilage risk. It helps processors ensure the safety of any new or reformulated product in which potentially hazardous microorganisms
might be present in low or incidental numbers. It also helps to determine whether a food or beverage has the ability to “kill off” any
pathogens that may have accidentally entered.
One of the issues when conducting challenge tests is how to inoculate the product with the organism or organisms being
used. It is important that the organisms are in a state similar to that found in the natural environment, that they are placed in the food or
drink in a way that duplicates how they may occur in nature, and that in doing this, the environment within the pack or container that holds
the food is not disturbed or changed in any way, as this may invalidate the test.
Problems with canned drinks
Canned drinks have always been problematic when setting up challenge tests. How is it possible to introduce the
challenging microorganism into the can? Piercing may introduce contamination and allows carbon dioxide (if carbonated) to escape and oxygen
to enter. These changes in conditions may allow organisms that would not normally grow in the product, to develop and give a misleading result.
In the past attempts have been made to aseptically dispense the can content into other sterile containers and inoculate these, however the
same problems of loss of carbonation (if the drink is carbonated) apply and it is very possible that misleading results could be
Dr Grzegorz Rachon, who leads the Brewing Microbiology Research team at Campden BRI, has developed techniques to
aseptically drill tiny holes in cans to quickly introduce the challenge organism. The hole is then sealed with a sterile metal rivet,
minimising any change to the conditions within the can. The drink remains carbonated, excess oxygen is not introduced and the rivet can
withstand the internal pressure of carbonation and any additional pressure that may build up from fermentation in case the challenge organism
is capable of growth.
The cans can be incubated for any length of time or at any temperature and finally opened and examined
microbiologically to establish if growth has occurred. This procedure gives the very best method for the realistic challenge testing of
carbonated drinks cans, eliminating the problems of previous methods and adding further to Campden BRI’s expertise in challenge testing.
How can we help
Challenge tests are now being conducted more frequently by the drinks industry. Knowing when to perform one, how to
design and conduct it and how to interpret the results, assists food processors in showing that their products are of high quality, stable
and safe. In addition, testing assures that regulatory mandates or finished product specifications are met. However, if food processors get
the process wrong, they may conclude that an unstable product is stable and hit major safety and quality issues when in production.
Our microbiologists are experts at challenge testing all types of food and drink, both for pathogens and spoilage
organisms. We have the knowledge of the correct processing and preservation systems, availability of predictive models and for the definitive
answer, the use of the best challenge testing protocols and experience available.
Basically, we wrote the book (
Campden BRI Guideline 63: Challenge testing protocols for assessing the safety and quality of food and drink), and we sit on both ISO and
EU committees writing the definitive standards for challenge testing.
Would you like to explore how challenge testing can help your business with one of our experienced microbiologists?
You can. (See what we did there?)
Contact us today for an initial free consultation to
discuss your beverage safety needs.
Grzegorz (Greg) has over 15 years of industry experience in Food, Drink and Pharmaceutical microbiology working for Leatherhead Food Research, Nelsons Natural
World and Thermo Fisher Scientific - Oxoid.
Challenge testing guideline
Find out more about our guideline on challenge testing protocols for assessing the safety and
quality of food and drink
How can we help you?
If you’d like to find out more about challenge testing, contact our support team to find
out how we can help.