Sep 3, 2026 - Foods
Ready meals: study shows risk from cross-contamination and cereulide
Ready-to-eat meals and takeaway food are often transported or stored for a certain period after preparation. Temperature, storage duration and type of packaging can have a significant impact on microbial safety.
A a recent experimental study published in the journal Food Microbiology examined these relationships using grilled pork. The focus was especially on possible cross-contamination via packaging and side dishes, and on formation of the emetic toxin cereulide by Bacillus cereus.
Cross-contamination possible despite sufficient heating
The pork was heated to a core temperature of 75 °C as part of the study. In the non‑artificially contaminated meat samples the aerobic total viable count subsequently remained below the detection limit of 0.7 log CFU/g.
The results, however, demonstrate that even sufficiently heated foods can become recontaminated after preparation. As possible routes of transmission, the researchers investigated, among other things, direct contact of the meat with contaminated packaging surfaces and side dishes.
Bacillus cereus: transfer from pasta to meat
In a further experiment, cooked pasta were intentionally contaminated with an emetic strain of Bacillus cereus and then packaged together with the grilled pork.
A transfer of Bacillus cereus from the pasta to the meat was observed. After 24 hours, counts in both the pasta and on the meat at 20 °C and 30 °C were markedly higher than after storage at 6 °C. Higher counts were also detected on the meat in closed packaging compared with open packaging systems.
Cereulide: heating offers no adequate protection after toxin formation
The emetic toxin cereulide produced by certain Bacillus cereus strains is of particular importance. The toxin is very heat‑stable. If it is already present in the food, it cannot be reliably inactivated by later reheating.
The study shows a clear influence of storage temperature: after 24 hours cereulide was not detected in either the pasta or the meat at 6 °C. At 20 °C and 30 °C the toxin was detectable in the pasta. Cereulide concentrations were also found on the originally uncontaminated pork after co‑storage with the pasta. The highest values in the meat were measured at 30 °C.
The results therefore underline the importance of short storage times and consistent cooling of ready‑to‑eat foods. In addition to hygienic preparation, possible cross‑contamination between individual components of a dish as well as the influence of packaging and storage conditions should be taken into account.
Microbiological testing at the BAV Institute
At the BAV Institute we daily test foods such as meat and meat products, delicatessen items, mixed salads, bakery and confectionery products as well as prepared meals and dishes for numerous microbiological parameters.
These include, among others, testing for presumptive Bacillus cereus as well as other hygiene, spoilage and pathogenic organisms such as Escherichia coli, Enterobacteriaceae, Listeria monocytogenes, Salmonella, STEC/VTEC/EHEC, Clostridium perfringens and coagulase‑positive staphylococci.
Tests can be carried out on the day of sample receipt or after storage under defined conditions, for example as part of best‑before (MHD) tests. On request, our customer advisors will evaluate the test results and support you with questions regarding the microbiological safety and marketability of your foods.
We also offer determination of cereulide by LC‑MS/MS. This enables targeted analysis of both Bacillus cereus and the heat‑stable toxin produced by emetic strains.
We provide fast and reliable results and are happy to advise you on any matters relating to product safety.
Source: