I've read that the ideal way to make stock is to:
- crack the large bones
- place the carcass in a stock pot
- cover with water
- bring it to a simmer (not a boil) on the stove
- place the whole thing in the oven on 180F for 6+ hours (possibly add vegetables an hour before you're done)
Apparently the temperature is key. You don't want it to go over 180F because that … does something to the stock. Harsher flavors or cloudy stock. Can't recall what.
After all of this cooking of stock is done, you want to preserve it. Canning seems ideal because it frees up freezer space. But would the canning process raise the temperature of the stock above that 180F mark that seems so critical?
Best Answer
The purpose of using a low simmer during stock-making is to avoid agitating the liquid. You want the fat to settle on top, but a rapid boil will simply disperse the fat and other impurities all throughout the stock, resulting in - as you've hinted at - a cloudy texture and possibly an inferior taste.
The other reason to avoid boiling is simply to prevent the stock from reducing too much. If you're simmering for 6 hours, you could lose all the water. If you leave the stock unattended during that time, and the water level drops too low, then you're not getting anything out of it; the water needs to be covering the bones in order to break down the collagen.
All that said, once you are finished with stock, you should have skimmed it and strained it through a fine sieve and probably a few layers of cheesecloth as well. If you've made your stock correctly, it will be clear and have (almost) no fat. Boiling it briefly at that point isn't really going to harm it; there's not enough fat left to cloud the stock and you're not boiling it for long enough to really reduce it.
So I would say go ahead and don't worry about the temperature. As far as I know, nothing magical happens at 180° F, that's just a rough temperature guideline for "low simmer".