I've been getting into making my own stocks and have decided to make a beef bone broth for the first time. I've been reading plenty of resources online however there are a lot conflicts from different sources. What I want to know is, what is the desirable temperature for cooking a bone broth over 12 hours without compromising the nutrients or gelatin?
I usually make my stocks on quite a low simmer - no continuous bubbling but rather a few bubbles every 2 or 3 seconds. I've noticed some websites advising to cook at a much higher temperature around 98 deg celsius, which is quite an aggressive rolling simmer just shy of a boil. I'm concerned about this because in my experience, such aggressive bubbling would make it difficult for the impurities and scum to float on top of the water (well to be fair, I do blanch my ingredients first to get rid of scum) but also because gelatin only needs to reach 82 deg celsius to dissolve, and you might break down the gelatin into histamines at such a high temperature. At the same time, there does seem to be some value in raising the temperature a little more than a low simmer as you can reduce the cooking time whilst not affecting the quality of the what you end up with much. Is there a sweet-spot between a low simmer and an aggressive simmer for optimal results?
My understanding is that simmering water and boiling water are both at (or very close to) 100C at sea level. The difference in effect on food and cooking is a result of the motion (or lack thereof) in the pot. I write "or very close to" because a rolling boil ensures there is efficient mixing of the ingredients in the pot, so the temperature throughout is more likely to equilibrate. The motion of a rolling boil also impacts the ingredients in the pot, which are pushed around and knocked into one another. Anyone knowledgeable in thermodynamics can correct me if I am misunderstanding.
I usually try to minimize the bouncing around when making stocks of any sort. I think (but this is anecdotal) that a more gentle approach leads to a clearer end product.