The Book of Household Management by Mrs. Beeton

methods of cooking animal food. To explain the philosophy of these simple culinary operations, we must advert to the effects that are produced by heat on the principal constituents of flesh. When finely-chopped mutton or beef is steeped for some time in a small quantity of clean water, and then subjected to slight pressure, the juice of the meat is extracted, and there is left a white tasteless residue, consisting chiefly of muscular fibres. When this residue is heated to between 158째 and 177째 Fahrenheit, the fibres shrink together, and become hard and horny. The influence of an elevated temperature on the soluble extract of flesh is not less remarkable. When the watery infusion, which contains all the savoury constituents of the meat, is gradually heated, it soon becomes turbid; and, when the temperature reaches 133째, flakes of whitish matter separate. These flakes are _albumen_, a substance precisely similar, in all its properties, to the white of egg (see No. 101). When the temperature of the watery extract is raised to 158째, the colouring matter of the blood coagulates, and the liquid, which was originally tinged red by this substance, is left perfectly clear, and almost colourless. When evaporated, even at a gentle heat, this residual liquid gradually becomes brown, and acquires the flavour of roast meat.