Expert warns Cooked pasta becomes poisonous if you store it incorrectly
At the end of September, a woman died after eating tortellini in a restaurant in Bavaria. Why? A food microbiologist explains how to store pasta properly.
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- Leftover pasta or rice can contain the bacterium Bacillus cereus, which survives even high temperatures and forms toxins when stored at too high temperatures.
- If you then reheat the leftovers from lunch or dinner, you can get food poisoning if the food is contaminated.
- Prof. Dr. Martin Loessner from ETH Zurich explains that leftover pasta or rice dishes should always be kept in the fridge.
- The term "fried rice syndrome" is often used when reheated leftovers cause illness.
Pasta is one of Mrs. and Mr. Swiss's favourite dishes. Quick and easy to prepare, pasta can be combined with a variety of sauces. So why not cook more so that there's something left to heat up tomorrow?
This is not a problem as long as the leftovers are stored properly, explains Martin Loessner, Professor of Food Science, Nutrition and Health at ETH Zurich.
In the worst-case scenario, reheated pasta or rice from the previous day can be fatal. "But this only happens very rarely. In most cases, the result is classic food poisoning," explains Loessner. This is often referred to as fried rice syndrome.
The culprit is a spore-forming bacterium known as Bacillus cereus. It lives in our food and is so resistant that it even survives cooking at high heat.
How does Bacillus cereus get into pasta?
But how does the bacterium get into pasta or rice in the first place? According to the expert, Bacillus cereus gets into the food through the soil and the environment, then lives on in it and produces toxins there under suitable conditions - so-called toxins - which humans ultimately ingest when eating. The result: you fall ill with food poisoning.
"Bacillus cereus is a very common bacterium in the environment that normally lives in the soil, can then be found in grain or rice and finally forms permanent forms called spores," Loessner explains further.
According to Loessner, these spores occur in almost all cases in flour or rice, for example, but the bacteria are only able to form toxins in around ten percent of cases.
Laypeople are often under the misconception that cooking pasta will kill off all possible dangers one way or another. "But that's wrong. Because these spores are so resistant, they survive even when rice or pasta is cooked."
What are the consequences?
The food microbiologist explains the whole process in more detail: "So if these spores have survived the heat and not all of the prepared food is consumed, but kept for another time, then a big mistake can happen. Because if the leftovers are not stored in the fridge, but simply somewhere in the kitchen with a lid, then the bacteria can grow very, very well, as all the competition from cooking has disappeared and made room for the Bacillus cereus."
The bacteria would then grow to very high numbers and start to produce toxins. "However, this only happens if we don't put the food in the fridge or if the fridge is faulty," the expert explains.
The target temperature of a refrigerator is four degrees. "The lower the temperature, the better."
The whole thing can only end fatally if very high doses of the poison have been ingested. "These toxins act extremely quickly. If they have been consumed in large quantities, there is little that can be done - the result is acute liver failure," says Loessner.
Which foods are affected?
The bacterium prefers to nest in "neutral foods" - such as rice, wheat or other cereal products. Vegetables also grow in the soil, but Bacillus cereus cannot thrive there.
Fruit is generally not affected as it is different and too acidic. "The acidity of fruit hinders the growth of the bacteria."
How can the bacteria be prevented from producing toxins?
Loessner praises one thing in particular when it comes to food storage: "It must be emphasized again and again that the refrigerator is the greatest invention ever for food safety."
After all, if leftover food is stored in a functioning refrigerator, all these concerns won't even exist. The bacteria can only grow at the wrong storage temperatures.
If stored correctly, leftovers can even be consumed for up to a week if you want to. "Then there's no need to worry, nothing can grow at the right cooling temperatures and the leftovers from lunch or dinner are then absolutely safe."
