Challenge testing

The impact of launching an unsafe product to the marketplace can be devastating.  Obtaining independent verification of product safety and stability is an essential part of the quality assurance process and is required by many major retailers.   Challenge testing remains a vital tool for the food industry to help establish food safety.

The process of challenge testing involves inoculating a food product with a known concentration of a particular ‘risk’ microorganism to assess if growth occurs during production, processing, distribution, storage or subsequent handling by the consumer. It is the ultimate evidence of the safety and microbiological stability of a food product or process.

At Leatherhead, we use real pathogens (as opposed to surrogate strains) including Listeria, E. coli and Salmonella, as well as spoilage microorganisms, sourced from our extensive culture collection established over many years.

We use challenge testing to:

  • Determine a product’s safety and stability during storage through to consumption
  • Establish a product’s shelf life
  • Aid product formulation in terms of intrinsic control factors (e.g. pH and water activity)
  • Establish critical points in a processing line (measuring process control factors such as temperature and time)
  • Determine microbial survival rates and microbial inactivation kinetics
  • Validate processing conditions on laboratory and pilot plant scale
  • Optimise processes and verify efficacy, covering safety, quality, stability, sensory and nutritional attributes
  • Investigate new materials and technologies for food packaging and processing

Examples include:

  • Evaluate the growth of Listeria monocytogenes in ready-to-eat products
  • Establish the effect of different modified atmosphere mixtures on the growth of pathogenic and spoilage organisms
  • Determine the effect of salt and vinegar on survival of Bacillus spp. during baking and shelf life in bread
  • Determine the effect of product reformulation with sugar reduction on the growth of pathogens in dairy products
  • Determine a safe pasteurisation process for a milk-based beverage
  • Confirm the lethality of a heat process in beverages
  • Investigate the effect of baking and alternative preservatives on germination and growth of Bacillus spp. in bread
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