eli5 : how come when you thaw out meat you’re not supposed to re-thaw it?


I’m not sure if this is true or not but it’s something I’ve heard when I was younger so I’ve just always taken it as a rule.
Is there a reason why you’re not supposed to re-freeze meat once it’s been thawed out?

In: 18

During the time spent thawing…and then the time spent to re-freeze, and then once again spend all the time to thaw the final time, the meat spends all that time within the temperature danger zone 40°-140° F …..allowing microbial (germ) growth during all three of those multiple hour periods of time. So it increases your odds of getting sick.

I mean if you’re just thawing it then re-freezing it straight away after, there’s minimal health risk, but the quality decreases because you lose moisture and momentarily increase oxidative changes to the fats and proteins that wouldn’t happen at a lower temperature.

As long as you are thawing food in the safe zone below 5c (so in the fridge) you can thaw and freeze as many times as you like. The texture of the food will degrade as cellular structures break down from freezing but it’s perfectly safe. Again, as long as its thawed below 5c.


Official recommendations often err on the side of caution, and for good reason, because you need to keep them simple enough for everyone to follow. The true story is usually more complicated, but it requires people to understand the issue to a more nuanced degree. You could give people a whole decision tree, but then the risk is some people will misunderstand and end up harming themselves.

In the case of thawing out meat, the big unknown that the official recommendation doesn’t want to deal with is: how are people thawing their meat? If you place your meat in the fridge and let it thaw there, that’s rather safe. For most of the process, the meat is colder than fridge temperature, and at most, it gets to the same temp, which is still as safe as the meat would be in the fridge in the first place.

However, if you are thawing your meat on the counter or in the microwave, that’s far less safe, because now you’re exposing parts of your meat to danger-zone temperatures (in which pathogens like bacteria can multiply) for some period of time. That’s okay if you don’t leave it there for too long before you cook and eat it, but if you were to then re-freeze it, now you’re freezing a piece of meat that potentially has substantial levels of pathogens in it. Some more pathogen growth might occur during the freezing process, and even if pathogen levels are still safe to eat once it is frozen again, but then the *next* time you thaw the meat, you may again be exposing it to danger-zone temperatures, and that might be the straw that breaks the camel’s back and raises pathogen levels to the point where they will make you sick.

(Even worse is if people are cooking the meat, eating some of it while the rest hangs out in the pot for a few hours, and *then* refreezing it. Danger zone temperatures galore, as well as contamination risk from cutting the meat, getting it in contact with other things, etc.)

In other words, you can roughly think of food as having a “spoilage clock” that runs at different speeds at different temperatures. It’s easy to give estimates of expiration date if you know what speed the clock will be running at. In the freezer? 3 months. In the fridge? One week. At room temp? Use within a day. But an unknown combination of all three? Who’s to say? No manufacturer or regulator wants to burn their hands on that. But if you’re careful about it, you might know that your food spent (say) two weeks in the freezer, and then one day in the fridge, so refreezing it should probably keep it for another month in the freezer and allow it to be thawed in the fridge one more time (still erring on the side of caution – also **note that these are made up numbers and not recommendations**).

People have mentioned germ growth, it’s actually enzyme activity.
Enzymes exist in a living body breaking down tissue which is replaced.
When the body dies the Enzymes continue their work but as the animal is dead the tissue doesn’t regrow.

The tissue has to be broken down by enzymes so that bacteria can consume the nutrients.
The first sign that the tissue is being broken down is the cellular release of liquid.
When you see liquid released the food isn’t rotten yet but it’s very close.

Enzyme activity is slowed by refrigeration and almost completely stopped by freezing.
The action of thawing will start up the enzyme activity with the fastest activity being above 5°C.

By refreezing and rethawing you are taking the food through the temperatures of the fastest enzyme activity.
It’s still not rotten but it’s pretty messed up and is just right for the bacteria to start multiplying.