On the composition of food and how it is adulterated : with practical directions for its analysis / by W. Marcet.

  • William Marcet
Date:
1856
Catalogue details

Licence: Public Domain Mark

Credit: On the composition of food and how it is adulterated : with practical directions for its analysis / by W. Marcet. Source: Wellcome Collection.

    34/236 page 14
    The average composition of bran is represented as follows, by Johnstone: Water . . . . 13-] Gluten and albumen, coagulated . . ]9*3 Oil 4-7 Husk and a little starch , . . 55-6 Baline matter (ash) . . . . 73 100-0 From the large quantity of gluten known to exist in bran, it may be concluded that, in the present system of grinding, the most nutritious portion of the grain is not contained in the flour. The husk in good wheat amounts on an average to fourteen or sixteen per cent, of the entire weight, though the quantity separated at the mill is often not more than one-ninth or eleven per cent. Microscopical characters of flour.—The microscope affords means of detecting readily any kind of flour from the form of its starch corpuscles. Wheaten flour is often adulterated with an inferior farina, so that it is of the greatest importance that the analyst should be acquainted with its microscopical character. The accompanying wood- cuts show the forms of the starch of wheat flour, potato flour, barley flour, rye flour, Indian corn flour, rice flour^ arrowroot^ sago, bean, oat, and pea. To obtain the starch for examination, let the flour be kneaded into a thin paste with water, and then squeezed through calico. To extract potato starch, pound the raw- potato in a mortar, and then strain the pulp through a cloth ; in every case the starch will fall to the bottom of the fluid, in a state fit for microscopical examination. If the observer should wish to see the starch granules in the vege- table cells, he must prepare a very thin section of the grain with a sharp knife or a razor \ place the section on the
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