Enriched flour is flour with specific nutrients returned to it that have been lost while being prepared. These restored nutrients include iron and B vitamins (folic acid, riboflavin, niacin, and thiamine). Calcium may also be supplemented. The purpose of enriching flour is to replenish the nutrients in the flour to match the nutritional status of the unrefined product. This differentiates enrichment from fortification, which is the process of introducing new nutrients to a food.
White flour became adopted in many cultures because it was recognized as being healthier than dark flours during the late Middle Ages. The unknown factor for its benefit at that time was that mold and fungus in the grains, which led to several diseases, were eliminated in the processing that resulted in white flour.
In the 1920s, Benjamin R. Jacobs began to document the loss of essential nutrients, however, through this processing of cereals and grains and to demonstrate a method by which the end products could be enriched with the lost nutrients. These nutrients promote good health and help to prevent some diseases.
The international effort to start enriching flour was launched during the 1940s as a means to improve the health of the wartime populations of the British and United States while food was being rationed and alternative sources of the nutrients were scarce. The decision to choose flour for enrichment was based on its commonality in the diets of those wartime populations, ranging from the rich to the poor. A major factor in the switch to enriched flour in the United States was the U.S. Army's restriction in 1942, that it would purchase only enriched flour.
The conversion of grains to flour involves several steps that vary with the type of grain used. The initial stages of processing remove the bran and the germ of the seed. The bran is the outermost layer of grains that contains fiber (primarily insoluble), some protein, and trace minerals. The germ is the embryo of the seed that contains B vitamins and trace minerals. Because the germ has a fat content of 10%, it may reduce shelf-life. Thus, it is separated to ensure longer shelf life of the flour. In contrast to enriched flour, whole wheat flour contains both the bran and the germ. The remaining and largest portion of the seed is the endosperm. It acts as a nutrient reservoir for the developing embryo. The endosperm contains a large amount of carbohydrates, protein, iron, B vitamins (niacin and riboflavin), and soluble fiber.
Once the endosperm is isolated, it is ground into a fine powder and sifted to remove any remaining fragments of bran or germ. Next, a chemical bleaching process with chlorine or benzoyl peroxide is used, to give the flour a whiter color. This bleaching step destroys many of the original nutrients that were present in the flour. The final flour product contains a smaller portion of the original nutrients that were present in the seed prior to processing. Enrichment ensures that these important nutrients are restored to improve the quality of the flour.
According to the FDA, a pound of enriched flour must have the following quantities of nutrients to qualify: 2.9 milligrams of thiamin, 1.8 milligrams of riboflavin, 24 milligrams of niacin, 0.7 milligrams of folic acid, and 20 milligrams of iron. The first four nutrients are B vitamins. Calcium also may be added; this must be to a minimum level of 960 milligrams per pound if calcium is mentioned in the labeling.
There has been much controversy regarding the benefits of enriched flour in relation to those of whole-wheat flour. Although enriched flour has similar amounts of vitamins to unrefined flour products, it does not have the same nutritional benefits of whole-wheat flour. One of the most significant differences is the amount of fiber. During the production of white enriched flour, the fiber-containing components (the bran and germ) are partially or wholly removed. Thus, products made from enriched flour contain less fiber than those made with whole-wheat flour. Another concern is effect on blood sugar levels; enriched flour products tend to be higher on the glycemic index, quickly raising blood sugar levels. In contrast, foods made from whole grains tend to be lower on the glycemic index. Since whole grains contain higher amounts of fiber and other complex carbohydrates, they take longer to digest; therefore, sugars enter the bloodstream in a slower and more controlled manner. A diet containing primarily low glycemic index foods has been related to many health benefits: reduced cholesterol levels, reduced risk of heart disease, and healthy weight loss.
Low glycemic index is not due to fiber but more likely starch structure. Grinding wheat to a fine powder (flour) breaks this structure, creating a higher index. Wholemeal bread differs little from white bread. Grainy breads containing fragments of bran and germ have a lower glycemic index due to the fragments, while semolina has a lower index than flour.