Does canning stock raise its temperature too high?

Question

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?

Answer 1

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".

Answer 2

A pressure canner can reach 240 degrees. However, the point of the 180 degree limit is probably to keep the bones from dissolving and the turkey fats & proteins from mixing into the broth and making it cloudy. Once you strain the broth, you won't have to worry about that anymore. Of course, you might then worry about what the 240 degrees does to the nutritional value of your stock, but... that's another question. One I don't have an answer for.

Answer 3

Canning stock once it has been created and finished doesn't cause extraction, agitation and cloudiness problems because the bones are gone, the extra proteins are removed, assuming you've clarified your stock and you are down to just stock.

The temperature above 180 problems relates to what happens during the extraction process, but once the extraction is done, you can pressure can your stock and keep it for as long as you need to. I do this with broth all the time, although I also freeze broth in ice cube trays so I will have small amounts as needed. And, yes, I know there is a difference between broth and stock, but I work mostly with broth that I make using a lot of bones AND meat, ending up with a gelatinous flavorful broth, rather than an unctuous stock.