Originally Posted by siniquezu
Thanks scott123. You mention that you try to get "good shade of color to my stock." Is that how you can tell that the broth has a very good amount of collogen in it? I know you can tell that you have a good amount of collagen in the broth when you are finished and it cools, it forms a gelatinous mass. Since there is no set amount of time for broth cooking, how can you tell when the broth has reached it maximum potential? Is it the color, the texture, the taste, or all of the above?
Siniquezu, what I said was I try to get a good color to my stock 'ingredients'
. In other words, I roast my bones/meat/skin very carefully to achieve a nice deep dark color, without burning anything. This is strictly from a flavor (maillard compound) perspective.
As far as how long to simmer a stock for full collagen extraction, well... there's very little agreement on that. Some chefs swear by 3 hours, some 6, some 24 and everything in between. Escoffier said 12 hours (or more). Here's my take on it.
As you simmer stock, collagen is being melted, maillard compounds (color/flavor) are being formed and, in the later stages, bone is being disintegrated.
So, if a perfectly white, clear stock is your goal, you don't roast the poultry bones/meat/skin, and you simmer it for a minimal amount of time to prevent bone disintegration (cloudiness) and color occuring. You also keep reduction to a minimum as that will produce color as well. From a perspective of collagen extraction, this approach is very ineffecient. It does produce a very delicate broth with a particular aesthetic that is appropriate for certain applications.
I, personally, am not that into white stocks. I like squeezing as much flavor and as much body as I can out of the materials at hand. I also tend to focus less on delicate cooking and more on rustic, hearty peasant food.
For me, a cloudy stock isn't the end of the world if I can pull more collagen out of my ingredients, so some bone disintegration is okay in my book. I do feel, though, that dissolved bone doesn't taste good (chalky, gamey) so when I simmer my stocks I strive for maximum collagen extraction with minimum bone disintegration.
For poultry stock, I use soft cartilage as my guide. The leg joint, the wing joint and the piece separating the two breasts. Once the soft cartilage is completely melted, that's when the first straining occurs. Sometimes it takes 6 hours to achieve this, sometimes longer, up to 8 or even 9 hours. If I go past that I find the bones will start falling apart and the taste of the stock compromised.
For beef stock, I don't have the cartilage for a visual clue, but I do have grizzle if I'm using meat (which I almost always do), so I try to dissolve all the grizzle. I also find beef bones a little less prone to dissolving than poultry so my beef stocks are simmered for longer periods of time, usually in the 9 hour realm.
I don't cover my bones completely with water as I find they collapse a bit/become submerged with a very brief amount of simmering. This decreased amount of water results in less time reducing down the line. If you're just starting to make stocks, then sure, cover your bones with water.
If your stock ingredients have either a good amount of skin (poultry) or connective tissue (beef) or veal bones, a final reduction to about 1/2 it's original volume should give you a good gel. If you're stuck with collagen deficient ingredients like clean beef bones, than I'd say 1/4 it's original volume will give you a good gel. Also, as you reduce stock, it will have subtle changes in viscosity that you'll be able to detect once you do it a few times.
As I said before, as you make more stocks, this will all be second nature to you. There is nothing better on this planet than homemade stock, so even if you don't get every bit of collagen possible, it will still raise the level of any dish you use it in.