Caramel II, (Caustic Sulfite Caramel) is obtained by treating edible carbohydrates of sugars, hydrolyzed starch, and molasses with sulfites (ammonium compount free) followed by heat treatment. Or it can be obtained by treating with sulfites, acids, or alkalis (free of ammonium compounds) followed by heat treatment.
Caramel coloring acts as an emulsifying agent that keeps flavor oils suspended in a solution. It is made by heating food-grade carbohydrates (such as corn syrup) to high temperatures. Usually an acid such as acetic, lactic or phosphoric acid is added to break the bonds between the sugars as it is heated to caramelization. The result is a burnt sugar that is the world’s most widely consumed (by weight) food coloring ingredient. It is not found only in colas, but also in sauces, gravies and baked goods.
One is called plain caramel.
A second involves reacting the sugar with sulfites.
A third is made be reacting sugars with ammonium compounds.
And in the fourth variety of caramel coloring--the kind used in Coke and Pepsi--sugars are reacted with both ammonium and sulfite compounds.
California public health officials recently placed 4-methylimidazole on the state's list of known carcinogens. Scientists at the University of California at Davis recently found significant levels of 4 methylimidazole in colas that far exceeds what the state considers to be safe. (Caramel IV)
You can find more information about Caramel Color and 4-methylimidazole in a petition to bar the use of caramel colorings... here.