Part 9

Albumen should always be prepared in such manner as to require the least possible expenditure of force in digestion. Those who are ill cannot afford to waste energy. Whether they are forced to do so in the digestion of their food depends very much upon the person who prepares it.

Advantage is often taken, in cooking, of the fact that albumen hardens on exposure to certain degrees of heat, to form protecting layers over pieces of broiling steak, roast meats, etc. If a piece of meat is placed in cold water to cook, it is evident, since albumen is soluble in cold water, that some of it will be wasted. If the same piece is plunged into boiling water the albumen in its outer layers will be immediately hardened, and form a sheath over the whole which will keep in the juices and the very important flavors. When broth or soup is made, we put the meat (cut into small pieces to expose a large extent of surface) into cold water, because we wish to draw out as much as possible the soluble matter and the flavors. If, on the other hand, the meat is to be served boiled, and broth or soup is not the object, then this order should be reversed, and every effort made to prevent the escape of any of the ingredients of the meat into the liquid.

In broiling steak, we sacrifice a thin layer of the outside to form a protecting covering over the whole by plunging it into the hottest part of the fire, so that the albumen will become suddenly hard and firm, and plug up the pores, thus preventing the savory juices from oozing out. More will be said on this subject in the recipes for cooking these kinds of foods.

=Gelatinoids.= The second class of protein compounds comprises the gelatinoids, gelatin being their leading constituent. It is found in flesh, tendons, cartilage and bone; in fact, it exists in all the tissues of the body, for the walls of most of the microscopic cells of which the tissues are composed contain gelatin.

=Exp.= Boil a pound of lean meat freed from tendons, fat, and bone, in a pint of water for three hours; then set the liquid away to cool. Jelly resembling calf's-foot jelly will be the result. The cell-walls of the flesh have been dissolved by the long-continued action of heat and liquid. This is commonly called stock or glaze.

=Exp.= Put a piece of clean bone into a dilute solution of hydrochloric acid. In two or three days the acid will have acted upon the earthy matters in the bone to remove them, and gelatin will remain. The average amount in bone is about thirty per cent.

Calves' feet were formerly used for jelly because of the excess of gelatin which they contain. They were cooked in water for a long time and the liquid reduced by further boiling; it was then clarified, flavored, and cooled; the result was a transparent, trembling jelly. The prepared gelatin of commerce, or gelatine, has now largely displaced this, for it is much more convenient to use, and less expensive.

=Extractives.= The extractives or flavoring properties of meats and other substances are usually classed with the protein compounds. Their chemical nature is not well understood.

FATS

=Fixed and Volatile Oils.= There are two classes of fats, called fixed oils and volatile oils. All kinds of fats good for food belong to the class of fixed oils. A volatile oil is one which evaporates away, like alcohol or water, and leaves no residue. The fixed oils, at least most of them, will not do this; they do not vaporize even at very high temperatures, but they become dissociated or decomposed,--that is, their chemical structure is broken up before their boiling-point is reached. Volatile oils, on the contrary, are capable of being boiled and transformed into gases. Some one illustrates this by the changes which take place in water. When water is heated to 212° Fahr. it is converted into a gas, which on cooling below 212° returns to the liquid state again without loss. The essential oil, turpentine, if heated to 320° Fahr. ceases to be a liquid and becomes a gas, which on cooling becomes a liquid oil again without loss of weight. Other volatile oils are oil of cloves, oil of bitter almonds, orange and lemon oil, oil of cinnamon, bergamot, and patchouli.

The boiling sometimes noticed in a pot of lard is owing to the presence in it of a little water which is very soon converted into steam, when the bubbling ceases, and after that the temperature of the fat rises rapidly, reaching in a short time four or five hundred degrees Fahrenheit, when a separation of its constituents takes place, and carbon is revealed as a black mass.

=Composition of Fats.= Fats are hydrocarbons--that is, they are composed chiefly of carbon united with hydrogen and oxygen. They must not be confounded with the carbohydrates, which are always composed of carbon with the elements of water--that is, the proportion of hydrogen to oxygen is as two to one,--whereas in the hydrocarbons this is not the case. These elements enter into the compositions of fats as various fatty acids and glycerin; the acids are not sour, as one would suppose from the name, but are so called because they behave chemically toward bases as sour acids do, that is, they unite with them. The glycerin of commerce is obtained by decomposing fats.

=Fat in Milk.= The white color of milk is given to it by minute globules of fat suspended in it.

=To prove this=: Put a little milk into a bottle with a ground-glass stopper; pour upon it three times its bulk of ether and shake gently; let it stand for two or three days, when it will be found that the ether has dissolved the fat and left a semi-transparent yellowish white liquid resembling blood serum. By pipetting or carefully pouring off the ether, and evaporating it by placing the vessel containing it in a dish of warm water, clear oil will be obtained. Care must be taken not to put the ether near a flame or the fire, as it is highly inflammable, and an explosion might occur. Ether boils at 94.82° Fahr.

The proportion of fat in milk is from 2.8 to 8 per cent. It varies in milk from different species of cows, and from the same species at different times, according to age, feeding, and other circumstances.

=Cream.= When milk is allowed to stand without disturbance for a time the globules of fat, being lighter than water, rise to the surface and form cream. Cream is the most wholesome, palatable, and easily digested form of fat. Butter is obtained by beating milk or cream in a churn until the little globules of fat break and stick together in a mass.

=Olive-Oil.= Olive-oil is one of the most easily digested and palatable of fats. A genuine oil of the first quality is, in this country unfortunately, expensive, much of that sold under the name being adulterated with cotton-seed oil, poppy-oil, and essence of lard.

Cotton-seed oil has no especially bad flavor, but it is unpleasant and indigestible when used raw as in sardines and salads. The after taste which it leaves reminds one too forcibly of castor-oil.

Olive-oil of the best quality is almost absolutely without flavor. It is prepared in several grades: the first pressing from the fruit is the best, the second is fair, the third inferior, and there is sometimes a fourth known as refuse oil. For deep fat frying nothing is so good as olive-oil, but its costliness in this country excludes it from common use.

The fat of the sheep and ox, after it has been rendered, and deprived of all membrane and fibers, is called tallow. The term is also applied to the fat of other animals, and to that of some plants, as bayberry-tallow, piny tallow, and others. The uncooked fat of any animal is called suet, but the name has come to be applied to the less easily melted kinds, which surround the kidneys or are in other parts of the loin. The fat which falls in drops from meat in roasting is called dripping.

THE CARBOHYDRATES

=Starch.= Starch is a substance found in wheat, corn, oats, and in fact in all grains, in potatoes, in the roots and stems of many plants, and in some fruits. In a pure state it is a white powder such as is seen in arrowroot and corn-starch. Examined by a microscope this powder is found to be made up of tiny grains of different shapes and sizes, some rounded or oval, others irregular. Those of potato-starch are ovoid, with an outside covering which appears to be folded or ridged, and looks somewhat like the outside of an oyster-shell, although its similarity extends no further than appearance, as the little ridges are true folds, and not overlapping edges.

=Size of Starch Grains.= Starch grains vary in size according to the source from which the starch is obtained. Those of ground rice are very small, being about 1/3000 of an inch in diameter; those of wheat are 1/1000 of an inch, and those of potato 1/300 of an inch.

Starch is a carbohydrate, being composed of six parts of carbon, ten of hydrogen, and five of oxygen. Its symbol is C{6}H{10}O_{5}. It is insoluble in water, but when the water is heated, the grains seem to absorb it; they increase in size, the ridges or folds disappear, and when the temperature reaches 140° Fahr. or a little over, they burst, and the contents mingle with the liquid forming the well-known paste.

=Test for Starch.= Mix a teaspoon of starch with a cup of cold water and boil them together for a few minutes until a paste is formed; then set it aside to cool. Meanwhile make a solution of iodine by putting a few flakes into alcohol, or use that which is already prepared, and which may be obtained at any pharmacy. Add a drop of this solution to the paste mixture; it will immediately color the whole a rich dark blue. This is known as the "iodine test," and is a very valuable one to the chemist, for by means of it the slightest trace of starch can be detected.

=Exp. with Arrowroot.= Make a thin paste by boiling a little arrowroot and water together. When cool test it with a drop of the iodine solution. The characteristic blue color will be very strong, showing that arrowroot is rich in starch.

Similar tests may be made with grated potato, wheat-flour, rice-flour, tapioca, and other starch-containing substances. Also powdered sugar, cream of tartar, and other substances may be tested, when it is suspected that they have been adulterated with starch.

Although starch grains burst and form a paste with water at 140° Fahr., that is not the temperature at which it should be cooked for food, and the thickening which then takes place should not be confounded, as often happens, with the true cooking of starch. In order to understand the difference between the proper cooking of starch and the simple bursting of the grains, let us consider the changes which take place in starch when it is subjected to different degrees of heat, and also those which are produced in it during the process of digestion. All starch in food is changed into dextrine and then into sugar (glucose, C{6}H{12}O_{6}) in the process of digestion. Glucose is a kind of sugar, resembling cane-sugar, but it is not so sweet.