Refreezing previously frozen food
One of the first things that i learned regarding food safety, etc. was to not refreeze food that has already been frozen. However, I'd like to know exactly why this is.
I know texture wise, things like fish don't hold up well. But, as far as making you sick. What's the reason.
Now to the reason for the question. I have a ham in the fridge. It was frozen sometime in April and is now thawed out and i am now eating on it. I am now faced with throwing the leftovers away, or can it be refrozen.
At the very least, i'd like to save the bone to throw in a pot of beans.
It's not always a food safety issue. Very small foods are less dangerous. Things that are only re-frozen once are less dangerous. Things that are vacuum sealed and thawed quickly under cold running water are less dangerous. But let's take a look at one situation where it is dangerous:
You freeze a chicken. It takes many hours for it to fully freeze. Then you thaw it in the fridge. Takes maybe two days to fully thaw, though during that time the surface of the chicken is at fridge temp, where spoilage bacteria can grow. You freeze it again - that's more time that the center is above freezing. Then you thaw it again - that's another couple days where the outside is at a temp where spoilage bacteria can grow.
See what I'm getting at? That bird is has now spent the equivalent of just shy of a week sitting in your refrigerator. And that's not even considering how long it spent in the market. So generally speaking, it's bad practice from a safety standpoint to freeze and thaw things repeatedly. In many circumstances you can get a away with it once or twice. But not indefinitely.
Refrigeration does not stop bacterial growth, it only slows it down.
However, if you handled the ham properly before freezing and this time around thawing in the fridge... there should be no real concern about food poisoning if you refreeze for another time.
If your ham is starting to get a little "old", I would use as much now (make soup, a pot of beans) and freeze that.... or just toss it.
It's mostly the texture/taste thing. The other reason is for foods that are more bacteria-friendly when thawed, so the concern is that the total time spent at active temperatures would be too risky (Lots of time for them to breed and produce toxins). Ham, with all its salt, is not one of those foods. But I'm not sure if you'll want to eat the re-frozen ham. No harm in trying.