I’ve got a gallon of milk that’s past its sell by date. I know it’ll still be good for another week or so, but I was wondering if I could give it another two weeks beyond that by putting it through another pasteurization process. I’m not sure if scaling will accomplish pasteurization, or if I would actually need to boil it.
Is this possible or would the milk undergo some chemical or structural breakdown that would make it unpalatable (for drinking)?
It would be drinkable, but it wouldn’t taste the same, it would have a “cooked” flavor.
This is similar to UHT milk in shelf-stable packaging.
Your biggest problem will be the storage container–it MUST be absolutely clean, and sealed well, or you can pick up contaminants just by keeping the milk in the fridge.
You can even can milk in a boiling water bath–I think.
~VOW
Spoiled food has two threats:
While reheating the milk could kill the baddies, it won’t get rid of toxins created by them.
Don’t do it.
I don’t know about milk specifically, but this kind of thing can happen for a pretty wide variety of foods.
Yes, but if she boils it *now–*past the sell-by date, prior to spoilage–how is this an issue?
And what, specifically, is a toxin?
Among others, you can get botulism, although by the time significant levels were reached, the milk was so spoiled nobody would ever think to drink it, boiled or not, and it only occurred when stored in warm conditions (none after 60 days at 6C/43F).
More realistically, milk that starts to smell and taste “off” has been contaminated with lactic-acid producing bacteria, which aren’t as dangerous, nor is the lactic acid they produce (your body produces it too).
Also, it surprises me at the number of questions about storing milk for weeks or more, since for me a gallon lasts for a few days.
You might be able to scald it, inoculate it with a yogurt culture and then eat the result. That might help it keep longer, since you’ve already spoiled it!
Or you could just buy a fresh 1/2 gallon this time.
What happens when milk goes bad - bacteria reproduce by splitting in 2. these organisms have to eat, which they do - the milk, lactose and butterfat. It’s a geomtric progression - 2,4,8,16, 32, 64, 128, 256… Once the level of bacteria is really high, and they’ve “processed” a lot of the milk, it’s too late. The milk is sour, clumping, turning to cheese.
Refrigerating slows this process because the bacteria grow and reproduce slower at lower temperatures.
the trick to pasteurizing or UHT is to heat the milk enough to kill most or all bacteria without burning the lactose (or “carmelizing” it). Then you have to maintain that sterile environment as long as possible; but you ahve to open the container (and let in contaminated air) to pour some milk out. I think pasteurizing is heating the milk to below boiling long enough to kill most bacteria, but not to the point where it can be sealed and stay for good for ages like canning. Then they rely on refrigeration to keep it good.
So you might be able to re-pasteurize before the milk “tastes bad”. Too hot, too long, and it no longer tastes like milk. Too little and it doesn’t kill enough bacteria. Modern plastic or wax cardboard containers are probably not designed for sterilization.
Oh the hell with this, I’ll just drink it.