Originally Posted by Andy M.
When making a basic stock, you only get gelatin if you include bones. Cooking just meat or veggies will give you a liquid broth.
Close, but... The gelatin is the result of melting the collagen, a cousin to protien. It is found in the connetive tissue between muscles. A roast with multiple muscles, like a beef shoulder, or chuck, will give you collagen, as will the connective tissue on short ribs. The bone marrow is also a good source of collagen, and is part of why you should break the bones in poultry when making a poultry broth, to extract and dissolve the marrow, and collagen. Also, any meat gristle, or cartilage is collagen based and will, after dissolving in boiling liquid, turn to gelatin. This is true of any meat, be it the Boston Butt from a pig, or the wing-tips of a chicken. Where there is marrow, ca cartilage, or marrow, you will dissolve the collagen in the simmering process.
Oh, and the gelatin is flavorless on its own. Think unflavored gelatin that you can purchase at the store. it has no flavor. However, the gelatin that is created by making a stock, or broth, will carry the flavor of the herbs, spices, and natural flavorings that are carried in the water. This is why the gelatinized broth from chicken tastes like chicken, and the geletinized broth from pork tastes like pork, and from beef, tastes like beaf, etc.
Veggies have no collagen and so don't make gelatin. When you eat Jello, you are eating unflavored gelatin, obtained by dissolving collagen and removing all other flavors from it, then adding flavoring and sugar. So, vegans can't be vegan if they eat Jello. But they can be if they use Agar Agar to make the gelatin, as it is a plant based gelatin that is similar to that obtained from animal collagen.
Seeeeeeya; Chief Longwind of the North