Contact person
Birgitta Bergström
Projektledare
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Challenge testing with microorganisms
Challenge testing is used for the practical assessment of growth, survival or reduction of relevant, pathogen or spoilage microorganisms when added to the actual product. It is an important tool when developing a new product or changning recipe.
Purpose
Why use a challengetest?
Sometimes it is desirable or necessary to verify a theoretical assessment of growth, survival or inhibition of microorganisms by performing a practical challengetest. The test can be used to assess if the product is safe with regard to inhibition of growth from a pathogen or to the spoilage flora to be able to say if the product has the expected shelf life.
It is possible to evaluate what happens when preservatives are added and/or the product is stored in different temperatures, maybe in combination with a specific packaging technique.
Method
How the test is done?
Microorganisms are carefully selected having a relevant origin and prehistory for the purpose of test to be done. The preferred pathogen or spoilage bacteria, yeast ond or mould are added to the product and the inoculated samples are stored under well defined temperature conditions before analysed at relevant time intervals. The challengetests are normally performed in the actual product, but sometimes it is more convinient to use a food model instead, mimicking the food composition.
Examples of challenge tests perfomed in our lab:
• Listeria monocytogenes in cold smoked salmon
• Clostridium botulinum in sausage batter after heat treatment
• Debaromyces, Zygosaccharomyces, Penicillium and Aspergillus in cold sauces, beverages
Effect from nitrite, NaCl, pH-value, sorbate, benzoate, lactate, protective cultures and MAP have been tested separately or in combination.
Deliveries
A challenge test is used to confirm or strengenth the result from a theoretical microbial risk assessment to secure the production of microbiologically shelf stable and safe food.
More information
We are regularly participating in The Swedish National Food Agency proficiency testing program for food microbiology to objectively prove our analytical competence.
Our lab are qualified to perform challenge tests and durability studies for assessing shelf-life of ready-to-eat foods related to Listeria monocytogenes according to EURL Lm TECHNICAL GUIDANCE DOCUMENT.
