When concentrated solution of sugars is heated to temperatures above 100 ° C, various thermal decomposition reactions can occur leading to formation of flavor compound and brown-colored products. When sucrose is heated to about 135 °C it melts and turns brown.
This process is called caramelization. Many carbohydrates undergo this process. Caramelization is accelerated by carboxylic acids and their salt, phosphate and metallic ion, but even when catalyzed, the energy requirements exceed those of a sugar-amine reactions.
If heating is continued the sugar becomes darker still, and eventually very pure carbon is obtained.
During caramelization, the first reaction step is the reversible isomerization of aldoses or ketoses in their open chain forms to form an enediol intermediate. Caramel has an attractive bitter sweet taste and a typical aroma.
This forms the basis of a whole industry dedicated to the production of caramel colors for food use, e.g. in cola beverages, beers, gravy browning.
Caramelization
