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.

    32/236 page 12
    The weight of the dextrine has been already deter- mined : it is the difference between that of the sugar and the weight of the residue left by the evaporation of the clear fluid; the total amount is to be calculated by a proportion similar to the above. The albumen of flour is usually weighed w^ith the dextrine. The quantity of fatty matters contained in a given amount of flour can be ascertained by treating a weighed quantity of flour with ether, evaporating this extract to dryness, and weighing the residue. The weight of the inorganic salts is determined by burning a known quantity of the flour. For the determination of the quantity and quality of gluten, an ingenious contrivance has been invented by Mr. Hubart, and termed the aleurometer, which is described in Dr. Hassall's book. It consists of a hollow copper cylinder, about six inches long, and from three quarters of an inch to an inch in diameter. It has two principal parts, the one, about two inches long, is closed at one end, forming a kind of cup capable of containing about 200 grains of fresh gluten ; it screws into the remainder of the cylinder. The cylinder being charged with gluten, is heated to about 420^ in an oil bath; by this treatment tho gluten swells more or less in the tube according to its quality; its increase or decrease in bulk may be measured with a graduated stem. Good flours furnish a gluten which augments to four or five times its original bulk; but bad flour gives a gluten which does not swell, becomes viscous and nearly fluid, adhering to the sides of the tube, and giving off occasionally a disagreeable odour, whilst that of good flour merely suggests the smell of hot bread. To this we may add, that the practical importance of the instrument is diminished by the necessity of separating the gluten from the flour pre-
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