The use of soft water for cooking purposes is always advisable; otherwise a longer period must be allowed. A preliminary boiling for a few minutes renders hard water softer, and the addition of a little carbonate of soda has a like effect.
When meat is inserted in water at a temperature below its boiling point, the juices are gradually extracted, while the meat is left a mass of indigestible fibres. A good soup is produced, but the meat is almost valueless. In order that the soups and broths may be nutritious, the less heat is employed in their preparation the better. If a soup is strained to make it clear, much of the most valuable part is removed.
Stewing is a process intermediate between boiling and baking. It possesses the great advantage over dry baking that no empyreumatic gases are produced, and there is no charring. The temperature of the stew-pan ought never to be above 180° Fahr.; at this heat the roughest and coarsest kinds of meat are made tender. The only objection to stewing is that the meat becomes saturated with fat and gravy, and is too rich for weak stomachs. It is advisable to stew lean meats only.
Hashing is a process of stewing applied to meat which has been previously cooked. The consequence of this double cooking, is that the meat becomes tough and leathery. A modified hash in which the meat is simply well warmed throughout is preferable.
Frying, unless carefully done, renders meat difficult of digestion, each fibre becoming coated with fat. The art is to “fry lightly,” that is, to burn quickly and evenly, so that no charring is produced. Two methods of frying are described. In the first, the substance to be fried, as an omelette or pancake, is placed with a little fat or oil in a frying-pan. This is really a modified process of roasting, the fat merely serving to prevent the object from adhering to the shallow pan. In the second, the substance to be fried is immersed in fat; for this purpose a frying kettle is required. Olive oil or good cotton seed oil is best for use in the frying-kettle. Lard is a bad material for frying; both it and butter are apt to burn unless heated slowly. Dripping is a good substance for frying. The fat used must be heated to from 350° to 390° F., and then the substance to be fried, e.g. a sole, plunged into it and left for two or three minutes. In this process the substance of the sole is really being steamed by the steam generated in the substance of the sole.
6. Broiling and Grilling are really processes of roasting applied to small portions of meat. In grilling, it is important that the gridiron should be hot before putting anything on it. An external coagulation of albumin is produced, as in good roasting and boiling.
The Cooking of Mixed Dishes.—A few instances may be given of common errors in preparing compound dishes. An egg in a custard, or just coagulated in a poached egg, is a light and easily-digested food; baked half an hour in a pudding, it is much less digestible; fried with ham, it is almost as indigestible as leather. Spices, if mixed with a dish before it is boiled, lose nearly all their flavouring power, while they remain irritating. They ought to be added near the end of the cooking process. A soup containing vegetables, as well as meat juices, should be prepared in two parts. The vegetables require prolonged boiling; gravy is spoilt by this. Similarly, the jam in a tartlet, if inserted before baking, loses its proper fruity flavour; and oysters baked in a beef-steak pie are indigestible.
The Cooking of Vegetable Foods.—Bread is either vesiculated or unvesiculated; the latter being what is called unleavened bread. Vesiculation of bread has usually been produced by fermentation of some of the sugar of the flour. The starch first becomes sugar (dextrose) and then the growth of the yeast plant in the dough splits this up into alcohol and carbonic acid gas. The carbonic acid percolates the substance of the dough, rendering it porous. When it has “risen” sufficiently, the dough is placed in the oven. The heat of the latter kills the yeast plant, thus preventing any further fermentation, but at the same time expands the carbonic acid gas in the bread, rendering the latter still more porous, and drives off in a gaseous condition the greater part of the alcohol produced by the previous fermentation.
It is objected to this plan of making bread, that a little of the sugar is wasted in producing alcohol and carbonic acid. To remedy this, another plan is sometimes adopted, as first proposed by Dr. Dauglish. In it the dough is charged with carbonic acid dissolved in water under considerable pressure. The gas escapes in the substance of the dough, and on baking expands as in the ordinary method of making bread. Bread made in this manner, is called “aerated bread.” Nevill’s bread has a solution of carbonate of ammonia incorporated in the dough, which is dissipated by heat, thus causing vesiculation of the bread.
On the continent, a mixture of hydrochloric acid and carbonate of soda is commonly used, carbonic acid and common salt being formed in the dough. Thus NaHCO₃ + HCl = NaCl + H₂O + CO₂. The hydrochloric acid employed should be perfectly pure and free from arsenic. Baking powders are also largely used for making cakes. “Self-raising” flour is flour with which baking-powder has already been mixed. Most baking-powders consist of a mixture of carbonate of soda and tartaric acid or bitartrate of potash, diluted with starch. When wetted, carbonic acid gas is evolved. A few contain alum, which is now an illegal material for this purpose.