Science - July 1, 2004

Food expert gives advice on how to avoid a holiday tummy

The holiday season is almost here, which means the annual Dutch migration to campgrounds is about to start. Associated with this phenomenon, is an increase in the number of cases of food poisoning. Wb asked Dr Rijkelt Beumer of the Food Microbiology Group whether diarrhoea is an unavoidable consequence of the summer here in the Lowlands.

“Once the temperature rises above 20 degrees, the number of food-related infections increases. It’s a simple fact of life: bacteria grow more quickly under warmer conditions. An added factor is that on holiday people pay less attention to hygiene, and then matters escalate.

An underestimated source is the open carton of milk, at least if you have opened it with your hands, even if it is sterilised milk. What many people forget is that we all carry dangerous bacteria; everyone has Staphylococcus aureus on their hands. If you open a carton of milk, or widen the opening, you can’t avoid transferring bacteria to the carton. A. aureus grows very quickly under warm conditions, and in a carton of milk there are lots of proteins present and no competitors: an ideal breeding ground. One day is enough to create sufficient toxins to make you feel pretty off-colour. Even boiling the milk won’t help, as the toxins are resistant to heat. The advice is don’t use your fingers to open a milk carton, and don’t keep an opened carton for longer than one day.

Raw meat is less of a problem. Meat already contains so many bacteria that S. aureus cannot stand up to the competition. In countries where you can buy meat in the markets, by the end of the day you can smell the decaying meat. The meat may be off, but if you cook it well, it is still safe to eat. Bacteria that live on meat do not give off substances that are dangerous to humans. Flies on the other hand can be a problem. Flies cannot absorb solid food, so what they do is to vomit over the food they have landed on. This makes the food fluid, so the flies can suck up what they need. The problem, however, is that the stomach contents of flies are neutral and therefore spread disease easily, especially as flies also eat from faeces of other animals and cover large distances.

What I don’t believe in is the stories that you can prevent food poisoning by eating certain foods. Beer is often mentioned. I have not done research on it, but I find it unlikely. How much alcohol is there in beer? About six percent? That’s not enough to kill bacteria. There are also stories about Coca Cola, and here there is a grain of truth. We have discovered that pathogens such as Salmonella and Shigella can be killed using Coca Cola, but it has to be Diet Coke. Ordinary Coke won’t work. The active ingredient in this case is the phosphoric acid in Diet Coke. The sugar in ordinary Coke neutralises the effect of the acid on bacteria.

But I wouldn’t rely on this. One mouthful of infected food can contain so many bacteria that you’d need a whole bottle of Diet Coke to kill the bacteria. Imagine the amount you’d have to drink to neutralise a whole meal! If you want to be certain to avoid food poisoning the only way is to ensure good hygiene. Wash your hands, cook meat thoroughly and keep food cool. That way your holiday should be pretty safe.”

Willem Koert

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