Bacterial spore contamination is a constant concern for food and ingredient companies. At the least, spore formers can spoil a batch of your product. At the worst – they can be pathogenic or produce dangerous, heat-stable toxins that pose a health risk to customers. In either case, they can cost you money, and threaten your brand reputation.

Switching to lower-heat processing or using new ingredients with problematic microbes may open the door to heat-resistant spores. You need to be able to assess and control the potential health and shelf-life risks of spores in your products, and identify ways to prevent future contaminations.

Food spoilers and health threats

When a product shows contamination, the first step is to identify the bacterial type to determine whether it poses a threat to health or risks spoiling your batch.

At NIZO, we begin by isolating the DNA and/or spoilage flora from your contaminated product. Using molecular techniques such as 16S rDNA analysis, we can identify the culprit even when the microbe is dead or not culturable. Translational bioinformatics gives us in-depth insight into the bacterium, including its ability to form heat-resistant spores, and its phylogenetic relations, safety classification and natural habitat. We can use this to pinpoint the likely source of contamination, which is critical to avoid a recurrence.

For heat-resistant spores in ingredients, we have worked with industry partners to develop reliable spore detection methods. These allow us to link initial spore levels in ingredients and heat processing conditions with the risk of spoilage to a finished product. This know-how also helps to set specifications on spores in ingredients.

Toxin producing Bacillus: wide-spread and heat-resistant

But what if the spore is dangerous, such as the widespread Bacillus cereus? This pathogen can form biofilms and produce toxins in food, including the heat-stable cereulide, which may cause food poisoning. Some B. cereus strains can grow and produce cereulide even at 7 °C – a common refrigeration temperature for many food products.

B. licheniformis and B. subtilis, on the other hand, can grow and produce heat-stable toxins at temperatures as high as the 55 °C commonly used in evaporators. And in some cases, they can even overgrow fermentations.

Our analytical methods enable us to detect and quantify cereulide, lichenysin and surfactin, which are produced by these Bacillus species. Combined with our microbial predictive models, we can help you to quickly evaluate the risk of survival, growth and toxin production during manufacturing and in your finished product throughout its shelf life.

We can also assess bacterial outgrowth in real products under realistic storage conditions, using our extensive bacterial culture collection, which includes toxin-producing strains. These tests can be done under controlled contamination conditions in our small-scale, high-throughput food application platform, as well as in larger-scale applications produced in our pilot plant.

Solutions that get to the root of the problem

Our models and methods offer powerful tools to assess the potential risks associated with pathogens and spoilers in your food product. But identifying and evaluating bacterial spore formers is only one part of control.

Bacterial spores can enter your product at any step in your production chain. Through our process scans and root cause analysis, for example using Whole Genome Sequencing for tracking and tracing, we can provide you with advice on structural solutions and process improvements. This helps you prevent a recurrence of the same problem in the future, and reliably bring a safe, high-quality product to the market.


  1. Wells-Bennik et al. Bacterial Spores in Food: Survival, Emergence, and Outgrowth. Annu Rev Food Sci Technol. 2016; 7: 457-82
  2. Eijlander et al. Spores in dairy – new insights in detection, enumeration and risk assessment. Int J Dairy Technol. 2019; 72(2): 303-315
  3. Eijlander et al. Enumeration and identification of bacterial spores in cocoa powders. J Food Prot. 2020; 83(9); 1530-1539.
  4. Wells-Bennik et al. Heat resistance of spores of 18 strains of Geobacillus stearothermophilus and impact of culturing conditions. Int J Food Microbiol. 2019; 291: 161-172.
  5. Berendsen et al. A mobile genetic element profoundly increases heat resistance of bacterial spores. The ISME Journal 2016; 10: 2633-2642.
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