Instructions: This article is excerpted from one entitled: "Oil Slick" but I am only sending that portion of the article in which a question is asked about the differences between bleached and unbleached flour.

Thought you people might be interested in the perspective of this chemist, Robert L. Wolke

QUESTION: How does bleached flour differ from unbleached flour? Unbleached wheat flour looks pretty white to me, so why do flour manufacturers bother with the bleaching step? Does the bleaching process leave any unsavory residues or leach out any nutrients?

ANSWER Wheat flour is naturally yellowish, but people apparently dont like yellow flour, except for the semolina used in pasta-making, which isnt usually bleached. Yellow bread and snow-white pasta wouldnt sell very well. If given half a chance, though, flour bleaches itself. That is, as it ages in air, the yellow color is oxidized away. But that takes time and time is money, so manufacturers speed up the process by using an oxidizing or bleaching agent such as potassium bromate (in which case the flour is said to be brominated), chlorine dioxide or benzoyl peroxide. These bleaching agents arent mere cosmetics. Flour that has been "aged," either naturally or by being treated with oxidizers, makes doughs that handle better and produce better bread.

Unbleached flour generally costs more than bleached flour because it has been whitened by natural aging, which entails the costs of storage.

Some people are concerned with the intimidating natures of these chemicals. But they are all unstable and, after doing their jobs, do not remain in the flour. The bromate, after reacting with the yellow compounds in the flour, is converted into harmless bromide. Chlorine dioxide is a gas that dissipates, so there is none of that left in the flour either. Any excess of benzoyl peroxide would decompose as soon as the flour is heated. The claim that bleaching flour destroys its Vitamin E is true but empty, because wheat flour contains negligible amounts of Vitamin E to begin with.

The Washington Post Company

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