When sugar is heated to about 170C, its molecule breaks down and the artifacts so generated recombine into compounds with characteristic color and flavor liked universally by most people. Basically the reaction is initiated by the removal of water from the sugar molecules, isomerization and polymerization into high molecular weight compounds of non-homogeneous nature. Since time immemorial caramel color as well as flavor were liked by the consumers, establishing it as a GRAS additive for addition in most foods consumed to day. Though there were periodic questions raised against uncontrolled use of caramel in a wide spectrum of foods, it is only recently that serious attempts are being made to curtail its use because of some studies highlighting its role in some health hazards, mainly based on animal experiments.
There are distinct four types of Caramel preparations with code numbers E150a, E150b, E150c and E150d, each with different properties and characteristics. By simply heating sugar without any additives yields the Type E150a, inclusion of sulfite compounds during heating generate Type 150b, use of Ammonia but without the presence of sulfites gives rise to Type 150c and if both Ammonia and Sulfites are used during the process Type 150d is formed. Alcoholic beverages like Whiskey incorporate Type150a caramel to provide the attractive mild brown color while Beer, synthetic soy sauce, confectionery etc contain Type 150c for the necessary color tint. Type 150d caramel is used extensively in acidic products like soft drinks and this version is considered the most dangerous by the toxicologists.
Due to persistent efforts by some consumer groups in some states in the US for banning this coloring substance, attention is being received at the national level to review its use in a limited way. The Food and Drug Administration of the US was petitioned recently by the reputed Center for Science in the Public Interest, long associated with efforts to ban potentially harmful foods, charging that the caramel coloring contains two cancer-causing chemicals, requesting that it should be banned. The chemicals in question are 2-methylimidazole (2-MEI) and 4-methylimidazole (4-MEI). Studies published in 2003 and 2005 by the National Toxicology Program of NIH are reported to have found that these chemicals caused cancer in some mice and rats and raises serious concerns regarding the advisability of continuing its uncontrolled use in various products, from pharmaceuticals to rubber. Other studies also found some evidence for cancer in lungs, liver, thyroid and leukemia in experimental animals. It may be illogical to take any risk whatsoever from a purely cosmetic coloring angle and such a situation may not justify the use of caramel in foods. As is to be expected beverage industry maintains that there's no evidence that the chemical, 4-MEI, causes cancer in humans but in its own interest it must take action to voluntarily cut down on the use of caramel in some of its products.
For some time there was this illusory feeling that caramel with a reported ADI of about 200 mg per kg body weight cannot cause any health damage. How ever with new scientific evidence emerging, even an exposure of 16 mcg per day is considered risky and therefore giving warning to consumers on the label of products with more than this limit may be an appropriate step to safe guard the safety of the consumers in the long run. Some cola beverages are known to contain more than 100 mcg of 4 -MEI alone per a 12 oz can and there may be many products which may contain this chemical, much more than this level.