New guide eases challenges of challenge testing

In the final part of our special edition on shelf life, we examine what challenge testing involves and look at how new guidance from the UK-based experts could provide a simple and standardised roadmap for all food processors to access this increasingly important instrument in the food safety toolkit.

Challenge testing​

Microbiological challenge testing is the laboratory simulation of what can happen to a food product during distribution and handling if it were to be contaminated with a micro-organism, Campden's Dr Gail Betts told FoodproductionDaily.com. It involves a series of experiments where the food is inoculated with the chosen organism, stored under specified conditions and examined for growth and toxin production.

The trend towards the growth in challenge testing is being driven by legislative pressure from the European Union to improve food safety, the need to comply with due diligence protocols, as well as the commercial imperative on food manufacturers to cut waste by extending shelf life, she added.

However, it can be a complex and difficult procedure for smaller companies. New challenge testing guidelines for laid out by the European Commission are thorough, they have been designed for experts in specialist laboratories and focus solely on Listeria monocytogenes, said the organisation's microbiological spoilage group manager.

“The Campden BRI method of challenge testing covers all potential microorganisms that companies may wish to consider and advocates the use of samples taken from a minimum of one batch with three to five replicates with less onus on achieving precise measurements of target inoculum level,” ​said Dr Betts. “This simplifies the challenge testing process, keeping costs down while still ensuring food safety legislative requirements are strictly adhered to.”​

Roadmap​

The guide – Challenge testing protocols for assessing the safety and quality of food and drink​ - details a number steps for the protocol, including defining the scope of the challenge test, reviewing product characteristics, as well as choosing the relevant organisms and number and identity of strains. It also examines culture maintenance, storage and product analysis.

The group said it hoped the guidance would be a roadmap for food manufacturers and retailers who wanted to initiate challenge testing.

​

“Retailers often have their own in-house protocols,”​ said Dr Betts. “If a manufacturer has to produce for a number of retailers they may be forced into a position where they use a number of different approaches. We are trying to develop an industry standard that will save time, administrative burden and costs.”​

The body stressed that while laboratory challenge testing was a very effective way of showing what could happen to a food product in the real world, it should not be undertaken gratuitously.

“When you carry out challenge testing, it is important to be clear about what questions you are trying to answer and what you are trying to achieve,”​ added Dr Betts. “It must have a direct relevance to the product; otherwise you run the risk of the testing being unnecessary and invalid. You could carry out challenge testing for 10 organisms in a foodstuff that may only ever be likely to contain two of them. We give guidance on what test to do for certain food types. This ensures companies get value for money while ensuring food safety.”​

Predictive testing​

Campden can also offering a microbial growth prediction service to assess shelf life. The body said it is a useful tool when there is insufficient time or resources to evaluate the impact of changes in product formulation or storage conditions. The computer-based model uses variables such as pH, proposed storage temperature and salt content to give a shelf-life estimate.

“These predictive models are by far 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,”​ said Dr Betts.

In effect, the process offers manufacturers a screening service to evaluate whether there is potential for spoilage due to pathogens – with the option of challenge testing if this proves to be the case.

Campden said the credibility of challenge testing has grown over the last decade as its accuracy and effectiveness has been proved.

“Industry acceptance for challenge testing has increased over the last ten years as companies have used them and then validated the results with their own analyses,”​ said Dr Betts