But using tougher foods does not mean you have to give up texture for the extra flavor; nor does intensity of flavor mean you have to have less subtlety. What it does mean is that you have to treat it differently from the way you treat "finer" foods.

1. www.gourmetrecipe.com
Why is soup so common in all the world's cultures? What is it about soup that makes it so appealing, regardless of what local
ingredients there are?
I think it is because every culture in history has had a "lower" class that has had to make do with the cheapest, least sought after
ingredients. Higher "quality" ingredients often have as much to do with texture as with flavor, and the richest people in any society get
the pick of the tenderest cuts of meat faranadoles, the finest spring vegetables, and the freshest fruit. In contrast, the "peasantry" lives
on the tougher cuts of meat, the bones often included, root vegetables and leftover fruit that has either been dried or fermented.
But these "lower" cuts of meat and root vegetables are not devoid of flavor, in fact they often have much more owing to what makes
them less desirable: their texture. Tougher foods are denser, and contain more flavor, more varied tissues, and often more nutrients.
Compare, for instance, an onion and an asparagus. Which has the more flavor? Sure, if you had to eat one raw you would probably
pick the asparagus. But ask your self which one you would give up for life if you had to!
But using tougher foods does not mean you have to give up texture for the extra flavor; nor does intensity of flavor mean you have to
have less subtlety. What it does mean is that you have to treat it differently from the way you treat "finer" foods.
For instance, a tenderloin, the tenderest cut of meat in most animals, is one that must be cooked quickly lest it get tough. But this type
of cooking does little for the flavor, as it has no time to develop or convert the flavors that already exist. Again, the finer cuts are more
about texture. But a flank steak, being much tougher already, benefits from a low, slow, wet cooking process that both extracts flavor
and reduces toughness. Soups and stews are perfect for this method, as is braising. What you end up with is something at least as
tasty as the tenderloin, and nearly as tender. And certainly cheaper!
Bones, gristle and similar tissues contain, among other things, collagen. This is a protein used in connective tissues, and it has some
very interesting properties. Firstly, it dissolves in hot liquid. Second, it coagulates when it cools down, provided it is concentrated
enough. If this makes it sound like gelatin, then you are correct: collagen is one of the main ingredients in gelatin. The third property of
collagen that is of interest in the kitchen is that is carries flavors that water cannot.
By extracting the collagen from bones and tough tissues, we can get a lot of flavor and nutrients that would otherwise be thrown away.
This can be done with any meat product. In restaurants, veal bones are often used for their high collagen content, but beef and
chicken are also very common. Fish and seafood stocks can be made from bones, gills, fins, and shells. Ham hocks are often used to
make a ham stock.