Is your ready-to-heat product safe after preparation?

Check these 4 things

1. Hot enough?

Is your product heated sufficiently after preparation to eliminate Listeria monocytogenes? Nikkelen: “That is the key question for ready-to-heat products. However, the line between ready-to-heat and ready-to-eat products is not always clear-cut. I have seen the NVWA (Netherlands Food and Consumer Product Safety Authority) classify certain ready-to-heat products as ready-to-eat, such as croquettes. What matters then is the extent to which your product supports the growth of Listeria monocytogenes, according to Regulation (EC) 2073/2005. Through a thorough study, such as predictive modeling or a challenge test, you must demonstrate that Listeria monocytogenes growth in ready-to-eat products remains below 0.5 log and does not exceed 100 CFU/g. With proper post-packaging pasteurisation, you eliminate the risk of recontamination, and safety is assured.”

Core temperature is key

Listeria monocytogenes rarely survives temperatures of 70 °C and above. “Check the core temperature when preparing your product in a worst-case scenario, meaning at the lowest recommended temperature or power setting. If the temperature does not rise above 60 °C, you may achieve insufficient reduction. In that case, adjust the preparation instructions. The goal is to achieve a core temperature of 70 °C for 2 minutes during the cooking process, or a validated equivalent.”

“The worst-case point is often the core, but not always. Especially not with microwave preparation.”

Check for cold spots

Measuring at multiple points is crucial. Nikkelen: “A product can sometimes have cold spots. That is why it is essential to monitor temperature variations across several points in the product throughout the preparation process. The worst-case point is often the core, but not always, especially not with microwave cooking.”

2. Clear preparation instructions?

“Did we have to think too much or hesitate while preparing the product? If so, it’s worth questioning whether the preparation instructions are clear enough. If not, update the instructions on the packaging. What we frequently see is that providing accurate preparation advice for natural products is challenging due to natural variability. Take potatoes, for instance: you have summer or winter harvests, or the variety changes. When that happens, the required cooking time changes too.”

“Are the baby potatoes still translucent on the inside? We evaluate the product after preparation.”

3. Edible and palatable?

“Is the product still edible and appealing for the consumer after preparation? By that, we mean neither burnt nor cold on the inside,” Nikkelen explains. “Evaluate the texture, aroma, colour, taste, and overall appearance.” Nikkelen and his team conduct these types of organoleptic tests for food producers and retailers as independent sensory assessors. The testing panel meets strict criteria; for example, testers must have no allergies, avoid drinking coffee, and refrain from smoking for at least 2 hours prior to the test.

“We are receiving more and more requests for organoleptic assessments because our clients value the independence of our evaluations. The findings provide valuable insights into the actual consumer experience. When strictly following the cooking instructions on the label, we sometimes find that baby potatoes remain glassy/translucent inside, peeled potatoes develop noticeable brown spots in residual skin areas, or the meatballs are hot while the mashed potatoes are still stone cold. In the latter scenario, it is insufficient to ensure the safety regarding Listeria monocytogenes.”

“Things can still go wrong at home in the consumer's kitchen.”

4. No acrylamide?

When baking or frying starchy foods at high temperatures, the carcinogenic substance acrylamide can form. Starchy foods include potato products, croquettes, bread, and biscuits. Consequently, issues can still arise at home in the consumer's kitchen. Nikkelen: “That is why food producers and retailers regularly ask us to take samples of products prepared strictly according to the on-pack instructions. We then analyse these samples for acrylamide. This allows you to verify whether the product complies with Regulation (EU) 2017/2158 even after consumer preparation.”

Asparagine and sugars

These starchy products contain reducing sugars as well as the amino acid asparagine. “For this type of product, it is best to keep temperatures lower and avoid over-baking or over-frying. While high temperatures make the product brown and deliciously crispy, they also lead to higher acrylamide levels. On the other hand, undercooking or using temperatures that are too low compromises taste, so striking the right balance is essential. We can also determine the levels of sugars and asparagine in your product beforehand. By reducing these parameters in the recipe formulation, you can achieve significant gains. If there is no free asparagine present in the product, the risk of acrylamide formation is virtually zero.”

“Pre-soaking potatoes in water or a citric acid solution can substantially reduce acrylamide levels in the finished product.”

Process modifications

You can also further reduce acrylamide levels in ready-to-heat / par-cooked products to ensure levels do not exceed safety benchmarks after final preparation. “Consider, for example, modifying your food manufacturing processes. Pre-soaking potatoes in water or a citric acid solution can substantially reduce the acrylamide content in the final product. Introducing varied processing steps, such as boiling, steaming, or sautéing ingredients in addition to baking and roasting, also helps minimise consumer intake of this carcinogenic compound,” says Nikkelen.