Beef Broth.

Good question gbhunter.

I know people will slather the bones with tomato paste as they are baking to enhance the brown color of the stock.

But I also know they will add tomatoes or tomato paste to the sauce mixture. I am not at all sure why. Maybe also for the color?

The stock pot
Stocks are nothing more than the results of an extraction process by which flavor and texture are rendered from animal and vegetable products. This blending of materials creates a liquid that can then be used as a flavoring and fortifying element in any finished product.
Numerous factors contribute to the complexity of the process, although the beginning of any stock is an extraction of bones, meat, mire poix (carrots, celery and onions in a specific ratio), aromatics (herbs), acids and water. The process becomes a bit more complex after this point, however, with such steps as roasting of the bones to create a caramelized effect. This step adds flavor and color to the stock, but a point of controversy among chefs is how long to roast the bones.

This is where the alchemy begins - the duration of the roasting time, the quantity of vegetables, the amount of water, the contents of the herb- and spice-filled sachet bag, and simmering time and temperature all affect the end product. The chef must rely greatly on past experience, as well as possess a clear understanding of raw ingredients and the changes they undergo in the cooking process. Experience may point to the need for tomato in a beef stock for the right acid balance, but trial and error surely lead to the refinements of concentrating the tomato (as in the modern use of tomato paste) and involving that tomato product in the caramelizing phase of bone roasting.

Aside from these amount and ingredient variables, a few constants are universally followed. It is generally agreed upon that starting with cold water, using bones that are high in collagen, and maintaining a low simmering temperature over a set period of time are the ground rules. After these rules are observed, the finishing, or personalizing, process is wide open. The length of time committed to roasting bones and vegetables can significantly change the end product, and should be dictated by the intended application of the stock being prepared.

IIRC, the acidity added by the tomato also influences the ability to clarify the stock later on.

So, I think that the answer is "flavor, color and clarity."

Agreed. Tomatoes are one method by which to add an acid to the stock. Depending on the dish, some dishes wouldn't taste appropriate without it.

my opinion:

tomatoes are a delicious dirty trick, they are loaded with free glutamates. Free glutamates are an excitotoxin very similar to MSG, but found naturally in tomatoes and mushrooms, among other things.

A little bit of tomato or mushroom cause a whole slew of biological occurances in the mouth. The taste buds become agitated, and foods taste MORE delicious than they did before, even without the presence of more flavor. Even a very small amount of the chemical will trick your tastebuds into firing, too much of it will kill your tastebuds.


Erik.