More and more regulations now also apply to ready-to-heat products

Ready to eat or ready to heat?

A meal salad is ready-to-eat (RTE). A microwave meal is ready-to-heat (RTH). Crystal clear, you might think, as are the specific regulatory requirements each product must meet, since distinct rules apply to both categories.

In practice, however, things look quite different. “We increasingly see that the NVWA (Netherlands Food and Consumer Product Safety Authority) interprets ready-to-heat products as ready-to-eat. As a result, EU Listeria legislation also applies to certain ready-to-heat foods. Manufacturers often only discover this during an NVWA audit.” How does this work, and how can you demonstrate that your ready-to-heat product is genuinely food-safe?

“You cannot simply assume that consumers will prepare the product exactly as stated on the packaging.” According to Marius Hagen, Consulting Team Lead at Eurofins Food Safety Solutions, this is the NVWA's core argument. “There is growing scrutiny on the food safety of unheated or par-cooked RTH products. For a long time, the prevailing mindset was ‘as long as the preparation instructions are on the label, we are covered.’ But those days are over, and that is a positive development. The step taken by consumers at home to make the product ready for consumption is an essential kill step to ensure a safe product,” explains Hagen.

Warm, but not hot enough

“First and foremost, it is essential that Listeria monocytogenes and other pathogens are eliminated either during the manufacturing process or via the recommended preparation instructions,” says Sandra Bokdam, Microbiology Project Leader at Eurofins Food Safety Solutions. That is less straightforward than it might seem. “Every oven and microwave operates differently and heats unevenly. Moreover, the question remains whether the consumer follows the cooking instructions properly and whether the food is still safe if prepared sub-optimally. There is even debate surrounding frozen croquettes: sometimes the inside gets warm, but not hot enough to eliminate pathogens.”

“The key question is whether consumers actually follow the cooking instructions correctly, and whether the food remains safe if they don't.”

Why you must prevent spore-forming bacteria in your product

While RTE legislation focuses primarily on Listeria monocytogenes, other pathogens pose significant risks as well, such as psychrotrophic Bacillus cereus and non-proteolytic Clostridium botulinum.

Bokdam: “Microwave meals frequently contain ingredients prone to Bacillus cereus contamination, such as pre-cooked rice. There is a risk that bacterial loads are insufficiently reduced during manufacturing, causing them to form endospores. Spore-forming bacteria survive thermal processes much more easily. Furthermore, these psychrotrophic strains can grow at temperatures as low as 4 °C, for instance, inside a consumer's refrigerator. If the subsequent preparation method used by the consumer fails to inactivate these psychrotrophic strains, you have a serious safety issue. Non-proteolytic Clostridium botulinum can likewise grow and produce neurotoxins at low temperatures in anaerobic (oxygen-free) environments, such as canned goods, processed meats, or vacuum-packed foods.”

Putting the manufacturing process under the microscope

“Examine your manufacturing process carefully and evaluate whether you achieve adequate spore inactivation using the proper time-temperature combinations,” advises Cathy De Graaf, also a Microbiology Project Leader at Eurofins Food Safety Solutions. “You can achieve this through predictive mathematical modeling by calculating the decimal reduction ($D$-value). For products where Bacillus cereus spores may be present, I subsequently recommend conducting a challenge test by inoculating the product matrix and simulating the actual production process. A model inherently provides less empirical certainty than a physical challenge test. An alternative approach is to use a validated surrogate organism, a non-pathogenic bacterium with identical thermal resistance characteristics, and run it through the actual processing line.”

“Examine the manufacturing process and evaluate whether you eliminate sufficient spores using the right temperature for the right duration.”

Bactericidal cooking validation

“Next, you evaluate whether the recommended preparation instructions achieve sufficient bacterial reduction and whether a worst-case heating scenario is adequate,” De Graaf continues. “By validating the cooking method, you prove that food safety is guaranteed. Are the preparation instructions straightforward to follow? What temperature variations occur across different consumer appliances? Investigate and validate core temperatures against the cooking instructions across diverse appliances: conventional ovens, stovetop pans, air fryers, deep fryers, and microwaves. Thorough validation eliminates as many microbiological hazards for the consumer as possible.”

As safe as possible

“It is a positive trend that both the manufacturing process and on-pack cooking advice are receiving more scrutiny to prevent spore-forming bacteria from proliferating,” says Hagen. “Make sure to provide clear instructions on the packaging designed to render the product microbiologically safe to eat, rather than vague guidelines merely meant for reheating. Microbiology is full of surprises: a process can run without issue for years, only to encounter unexpected contamination when conditions change or new raw materials are introduced. Absolute zero risk does not exist, but we can minimise the hazards.”

“Provide clear cooking instructions on the packaging that effectively achieve a kill step, rather than merely suggesting how to warm the product up.”