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HOW do you know when a piece of chicken is cooked? Most people think you can tell by looking at the colour, but it turns out this isn鈥檛 reliable.

Chicken is one of the riskiest foods for Salmonella and Campylobacter, two of the biggest causes of food-borne illness. These bacteria can be found on the inside of chicken meat, which is why chicken must be cooked through, unlike beef.

Muscle tissue changes colour when myoglobin, an oxygen-binding pigment similar to haemoglobin, is denatured. Chicken muscle, however, contains less myoglobin than most other kinds of meat, so the colour change is less pronounced 鈥� and recent research shows that it happens before harmful bacteria have been eliminated.

In a 2020 , at the Norwegian Institute of Food, Fisheries and Aquaculture and her colleagues injected chicken breast fillets with Salmonella and Campylobacter. They cooked the fillets between two grill plates until they reached core temperatures between 50 and 70掳C (122 and 158掳F). Samples from the core and the surface of the meat were taken for analysis.

According to guidelines from the World Health Organization, chicken should be cooked to 70掳C in order to be safe. But the team found that most of the colour change happened below 55掳C (131掳F). Clear juices can鈥檛 be relied on either: even at 50掳C, the colour of the fluid was too pale for the instrument to detect.

Using a kitchen thermometer can help make sure food is safe, but there are problems with this method too. Langsrud and her team tested five thermometers marketed at consumers. All but the cheapest one were reasonably accurate, but even the more expensive ones took between 4 and 15 seconds to give an accurate reading. You also have to test the meat in several places to make sure you have found the coldest part.

Worryingly, even when the core temperature of the fillets reached 70掳C, some bacteria survived on the surface of the sides of the meat, which weren鈥檛 in contact with the grill plate. Langsrud says bacteria are found in higher numbers on the surface of meat than the interior, so the most important thing is to make sure that chicken is cooked on all sides. 鈥淚 would guess that when people get sick, it鈥檚 most often because they eat something that鈥檚 partly raw on the outside,鈥� she says.

Perhaps the safest ways to cook chicken, then, are those in which the meat is braised in a sauce or poached in water. To poach two chicken breasts, cover them with cold water in a saucepan with a tablespoon of salt. Bring to a simmer, keep it simmering for 10 minutes, then turn off the heat. Flip the breasts over, cover with a lid and leave for 15 minutes. Ideally, check the core temperature with a good thermometer.

Sam Wong is assistant news editor and self-appointed chief gourmand at 快猫短视频. Follow him @samwong1

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