What is Low-temperature Slow Cooking?


In recent years, many restaurants have added “slow-cooked” items to their menus, and there are also slow cookers on the market that are popular among gourmets. It is true that slow cooking can retain the original flavour and taste of the ingredients and keep the meat tender. However, does this way of cooking harbour any food safety risks if the cooking temperature is not well-controlled?


Slow cooking refers to the process in which food is vacuum-sealed in an airtight bag and placed in a temperature-controlled water bath for an extended period of time. The vacuum environment and the water bath reduce the exposure of food to oxygen during the heating process and keep it moist. At the same time, low-temperature heating avoids the risk of overcooking which usually results in an unpleasant texture.


Nevertheless, as food is cooked at a lower temperature when it is slow-cooked, it is likely to be undercooked if it is not heated for long enough and therefore still carries pathogens and parasites. This makes the temperature and time control all the more important. The range between 5℃ to 60℃ is known as the temperature danger zone in cooking, in which microbes multiply rapidly. This is why the water temperature in slow cooking must be kept above 60℃ for a sufficient period of time to lower food safety risks.


Moreover, high-risk individuals including children, the elderly, pregnant women, and people with a compromised immune system should avoid having slow-cooked food since it is hard to ensure that the pathogens and parasites in food have been killed by cooking at low temperatures.


Slow-cooking ingredients that may contain parasites, such as seafood and pork, is not advisable because the parasites cannot be completely killed at a low temperature. Beans are not suitable for slow cooking as well since they contain phytohemagglutinin (PHA), which causes nausea, vomiting and diarrhoea, etc. shortly after consumption and can only be destroyed at high temperature.


Last but not least, ingredients to be slow-cooked should be cut into proper sizes to increase the surface area so that they can be properly heated. When preparing the ingredients, separate utensils, such as containers and knives, should be used for raw and cooked food in order to avoid cross-contamination. Washing hands thoroughly before and after preparing the ingredients, as well as before eating, is also advised. Attention must be paid to each step in slow cooking in order to ensure the safety of slow-cooked food.