Consumers world over prefer white flour and the food processing industry takes advantage of this weakness by providing highly refined flour through use of chemicals. The use of flour bleaching agents became a controversial issue when serious questions were raised in China regarding the safety of these chemicals when consumed over a period of time. Added to this Chinese authorities were appalled to find widespread use of Lime powder along with Benzoyl Peroxide by the flour mill industry there for obtaining snow white flour, in great demand for making many wheat based products. While Benzoyl Peroxide is a permitted bleaching agent permitted in many parts of the world, Lime powder is considered dangerous if present in flour as it can cause severe respiratory problems causing even death.
The burning question is why the flour has to be chemically bleached at all when nature itself has provided a process of whitening by exposure to atmospheric oxygen. But the industry has neither the time nor the patience to keep the flour for months together for natural aging, probably because of financial implications of long time storage. Natural flour has an yellow tint due to the presence of Xanthophyll carotenoids but if refined flour is produced in modern flour mills removing practically all the bran and the germ, the flour may look whiter. Industry still uses bleaching chemicals for further improving the appearance besides making the flour better "functionally" . Is it not unfortunate that modern flour mills produce the so called white flours by sacrificing many of the nutrients in the process, depriving the consumer of these critical life supporting nutrients?
Talking about nutrient loss, the modern day mills in contrast to traditional Atta Chakkis, remove almost all Vitamin E, 50% of unsaturated fats, 50% of Calcium, 70% of Phosphorus, 80% of Iron, 98% of Magnesium, 75% of Manganese, 50% of Potassium, 65% of Copper, 80% of Thiamine, 60% of Ribiflavin, 75% of Niacin, 50% of Pantothenic acid, 50% of Pyridoxine and practically all the dietary fiber making it literally a "dead" material. In a country like the US some of the lost nutrients are added back and offered to the consumer as "enriched" flour! According to many scientific studies such tampering with the natural composition of wheat can have grave implications on the consumer. It has been proved that those consuming calories through such refined products as bleached flour have a tendency to put on unwanted weight while the equivalent amount of calories taken through whole grain flour, nuts, fruits and vegetables do not cause such aberrations. The rapid rate at which glucose is generated in the blood from ingested refined foods causes significant metabolic changes causing over production of insulin by the pancreas leading to more and more food consumption.
Flour bleaching agents such as Benzoyl Peroxide, Calcium Peroxide, Nitrogen Dioxide, Chlorine, Chlorine Dioxide, Azo Dicarbamide etc are used for obtaining white flour and these chemicals bleach the surface of flour particles giving an illusion of a uniformly white and bright product. Chlorine, Bromates and Peroxides are not permitted in EU countries because of their suspected role in causing health problems on continuous consumption. According industry sources bleached flour gives higher loaf volume and fine grain structure in bread though it can also leave a bitter after-taste. In China Benzoyl Peroxide is permitted to be used at 0.06% in flour products though there is clamor for banning this bleaching agent because of its uncertain safety.
Interestingly due to continuous consumer pressure and proven advantage of whole wheat flour, food industry in many countries are switching over to technologies that can make good quality bread from such flours, though sandwich breads are still made from bleached and enriched white flour. Indians consume wheat mainly in the form of Atta, the local name for whole wheat flour which is used to make flat bread or roti and it is recognized that modern roller flour mills can make only resultant Atta which is a blend of refined flour and finely ground bran fraction but can at best be a poor substitute for natural Atta. It is a tribute to traditional chakkis or plate mills that a good quality Atta can be made only if the wheat is ground in this simple mill and most large scale millers are using giant chakkis in battery to manufacture large quantities of the popular roti flour in the country.