Heating of carbohydrates, in particular sucrose (see Sec. 4.2.3) and reducing sugars, without nitrogen-containing compounds
effects a complex group of reactions termed caramelization. Reaction is facilitated by small amounts of acids and certain salts.
Mostly thermolysis causes dehydration of the sugar molecule with introduction of double bonds or formation of anhydro rings.
Introduction of double bonds leads to unsaturated rings such as furans. Conjugated double bonds absorb light and produce
color. Often unsaturated rings will condense to polymers yielding useful colors. Catalysts increase the reaction rate and are often
used to direct the reaction to specific types of caramel colors, solubilities, and acidities.