Ask the Skeptic - Reheating Meat
This is a new recurring weekly segment for the SGU Science News Page. Each week I’ll answer a listener/reader’s burning science, paranormal, or critical thinking question. This week – how unsafe is partially reheating meat?
Hello folks,Love the show, have been listening for about 6 months. Please could you explain the following to me. On my lunch break, a colleague accosted me about whether my chicken was fully reheated and we proceeded to debate whether it actually mattered.The problem is this;Most people (including the UK Food Standards Agency) say that meat should be fully reheated until it is piping hot so that it is safe to eat. My issue with this is that the bacteria have ideal conditions for reproduction whilst the chicken is cooling down after the initial cooking. Surely they don’t have enough time in the 2 minutes in the microwave to rapidly reproduce and make you ill?Therefore how is half-reheating chicken any worse than eating cold, cooked chicken?Cold chicken is served in sandwiches and many other dishes, and I have never had a problem from eating either cold or half-reheated chicken. I can understand the problem with reheating meat several times, or reheating it halfway and then putting it back in the fridge, but I don’t see why it would matter half-reheating it and eating it in its entirety after the initial cooking if eating it cold is fine.I’ve tried to find studies on this, but to no avail. Please could you bust this myth, or explain to me why I’m being a total idiot and not seeing the obvious problemRegards,Tony from London.
That’s a great question, with a practical answer.
Some foods harbor potentially harmful bacteria. Improper cooking, storing, reheating, or serving the food could allow for bacteria to reproduce to large enough numbers to be harmful. Bacteria can cause illness either by causing an infection, or through the toxins they release into the food (botulism, for example).
Meats, foods that contain meats, and liquid foods like broths and stews are especially vulnerable to bacteria.
Bacteria can reproduce between 5 degrees C (40 degrees F) and 60 degrees C (140 degrees F). Above 60C/140F bacteria will no longer reproduce, but it takes 75C/165F to kill bacteria.
The recommendation is to thoroughly cook food to a high enough temperature throughout to kill existing bacteria. Using a thermometer is the best way to ensure a high enough temperature has been achieved. During food preparation, minimize contamination from raw food and thoroughly clean any surfaces and implements. (So don’t cut your vegetables on the same cutting board on which you just cut up raw chicken.)
Once the food is cooked, keep it above 60C/140F to keep any bacteria that have not been killed from reproducing.
Any food that is not consumed that you want to store for later use should be rapidly cooled – down to 5C/40F over less than 6 hours. Place the food right away in a refrigerator, and maximize surface area by storing liquids in shallow containers and cutting up large pieces of meat or food.
When reheating food, again reheat rapidly, preferably to above 75C/165F to kill any bacteria that formed during the cooling and reheating process. And again maintain above 60C/140F until used.
Here is where I think Tony’s confusion stems from. The above guidelines are designed to apply to restaurants, when serving multiple people at events, or any other food service. When food is going to be heated and served immediately, there will not be time for bacteria to form.
It is safe to eat cold meat that has been thoroughly cooked and then rapidly cooled. If the meat was left out for a couple hours after cooking and before being placed in the fridge, then bacteria may have had time to significantly reproduce. The same is true if a large leftover turkey, for example, were placed in the fridge and the center took many hours to cool sufficiently to prevent reproduction.
So there are times when that cold meat may not be safe, and thoroughly reheating to a bacteria-killing 75C/165F is recommended. If, however, the meat is thoroughly cooked, did not spend much time in the danger zone temperature, and was rapidly cooled, it is probably safe to eat cold or partially reheated, as long as it is consumed immediately.