Include bone marrow when making stock?
When making stock, when you think about it, shouldn't you NOT include marrow?
This question really only applies to beef and veal stock, since chicken bones are too small for you to be able to scoop out the marrow.
I've been thinking, shouldn't you scoop out the marrow before you make stock with bones? Won't the marrow just make the stock cloudy and/or add weird little chunks to it? And most of the gelatin and flavor comes from the meat and bone - it seems to me, as tasty as marrow is, it would be an "off" flavor in stock, which is just supposed to taste meaty. And marrow will just add more to the fat that needs to be scooped out later. Does the flavor of the marrow even go into the stock? Wouldn't it not since oil and water don't mix (and marrow is mostly oil/fat)?
I roast the bones, then put them into the stock pot and cook with the rest of the ingredients. They get strained out when the stock is done. If the stock is cooked slowly on low heat the coligen melts into the stock liquid and enhances the flavor.
As long as the bones aren't cracked, the marrow shouldn't really come out in the way you're describing. Heck, maybe the bones filter the marrow? Either way, I've never scooped the marrow out of my soup bones. If you really want to be hardcore classical, you could always do the egg white raft after to clarify and remove guck like that.
If chefs or home cooks had to scoop out marrow from legs bones before making stock, stock would cease to be made. Simply put, too much work.
Marrow is the fatty network of connective tissue inside bones, which produces red blood cells. Slowly simmering the stock allows the collagen ( collagen is synthesized in bone marrow, and found elsewhere in the bones and carilage) to melt into the stock and enhance flavor and texture. The bones are not usually cracked before making stock, although sawed bones will have marrow exposed, the marrow is not removed before making stock, it doesn't leave weird chunks in the stock, it doesn't leave an "off" flavor in the stock, but rather enhances the flavor, it will still be contained in the bones when you remove them from the stock (as you can see by observing the cut end of the bone) after simmering the prescribed length of time. As for fat content, bone marrow is comprised of red hematopoietic tissue, and yellow marrow, which is fat cells. So marrow is not all fat.
Forget about the marrow. It's an integral part of the stock process.
I would never make a conscious effort to remove the marrow.
Part of the reason is that I don't care what my stock LOOKS like -- either cloudy or crystal clear.
I only care about how my stock TASTES like, and in my opinion the marrow definitely adds flavor.