Can one preserve food by periodically heating it


I get that keeping food temperature low will slow down chemical reactions and preserve food, but sometimes my sister preserves food by heating it every 6 hours or so (up to 1-2 days). Does this help preserving the food? If yes, how does it work?

If it matters, the food currently in question is this one, but I would appreciate a general explanation. In case anyone is wondering, she doesn't store it in the fridge because it is full.

Best Answer

YES! If food is quickly heated and kept above 140F/60C, microorganisms can't grow in the food. Professional kitchens use steam tables to keep food warm at this temperature throughout a day's service. If the product is cooled quickly (generally using an ice bath), then it can be used for more than one day.

Another approach is often used for stocks and soups: heat them to 165F/75C daily or every two days, to kill microorganisms, then cool them quickly with an ice bath to under 40F/5C. This can be done 2-3 times to extend the fridge life of the product.

The most important part of both approaches is to use a food thermometer to verify that food is fully heated/cooled, and to make sure that heating and cooling is done QUICKLY. For food safety, you do not want food to be in the 40F/5C to 140F/60C range for more than an hour if possible, or two hours tops.

Another trick to extend the fridge life of food is to immediately transfer it from a still-hot pot to a cool container, and then leave the top of the container open to allow steam to escape. This greatly reduces cooling time; even in a refrigerator, a sealed container may take over an hour to cool down to a safe temperature.