47. Flour.—The flour of wheat is that usually employed for making bread in this country. Wheaten flour, like all valuable foods, consists of several distinct substances. These may be separated from each other very readily.
If a little dough, made of moistened flour, is tied up in a piece of muslin, and kneaded for some time between the fingers in a large basin of water, the latter becomes milky from the starch of the flour being washed out into it. If this water is allowed to stand at rest, the starch settles at the bottom in the form of a fine white powder. The water contains dissolved in it a small quantity of sugar, gum, and the other soluble substances of the flour.
When the whole of the starch has been washed through the muslin, a greyish tough substance, like very soft indiarubber remains. This is gluten, which forms about 10 per cent. of the flour, the starch being nearly 70 per cent., and the sugar and gum 7 per cent., the remaining parts being made up of water, mineral substances, and indigestible fibre.