The amount of nutriment to be got from a simple soup is very small. Soupmaking proceeds upon the principle of taking as much as possible from the materials, the extraction being effected by the use of a considerable quantity of water at a very moderate heat, extending over a long time. A clear soup contains the flavouring constituents and some of the salts of the meat of which it is prepared, also a very small proportion of soluble protein, all the coagulated protein having floated to the top and been removed as a brownish scum during the making; there is also present a small quantity of fat. Most clear soups contain only from 1 to 2 per cent, of solids; thick soups contain a little more, as may be seen from the following analysis by Konig: -
Other Nitrogen-free Substances.
Pea Soup .
If soup is to be made even moderately nutritious, the soup must simply be used as a vehicle by means of which other food materials can be made use of. The following ingredients are frequently used to thicken soup: - Starchy materials, such as cornflour, barley, rice, and potatoes; macaroni and vermicelli, both containing a good deal of gluten. The pulses, e.g., lentils, peas, beans, added to weak stock, produce the most nutritious soups to be found on the table. Eggs, grated cheese, and cream have all their places in the preparation of nutritious soups. Purees of meat, chicken, game, and fish can also be added to soup.
In spite of its low nutritional value, clear soup has its own place in dietetics. To begin dinner with, a small quantity (8 to 10 oz.) of soup is a good method; it promotes the gastric secretion, and consequently aids the digestion of the meal that follows. A larger quantity may be a drawback to digestion, on account of diluting the gastric juice. For some invalids a strong soup is useful as a stimulant for rousing the appetite and increasing the digestive powers, but it does not count for much as nutriment.
In order to expose as large a surface to the water as possible, the meat is cut up into pieces; the solvent power of the water is increased by the addition of a little vinegar to the water. The temperature is kept at a little below 160° F. for several hours. As vegetables require a very much greater heat than this to soften them, they should cither be first boiled, and then the meat should be added, or the vegetables can be cooked separately, and only added to the soup when it is almost ready; this preserves the colour best. Flavouring herbs should be put in at the last moment. In all soups made from meat, great care should be exercised in the removal of the fat. This is done by the soup being made the day before it is required, put aside in a basin to cool, and, when quite cold, the fat carefully skimmed from the top.
The term "stock" is usually given to the liquid part, to which the nutritious thickening and other ingredients are added.
Stock is the foundation of soups, and to be successful in soupmaking the manufacture of stock is necessary. There are varieties of stock, i.e., white, brown, and fish stock. Of white and brown a first and second stock is made.
White stock is made principally from beef, with sometimes a little mutton or veal added.
Brown stock is made in the same way as white, but more vegetables are added to colour it.
Fish stock is made from fish and fish trimmings.
"Meat boilings" is the name given to the water in which a joint of meat, fowl, or rabbit has been boiled.
Consomme is a clear soup made from first stock, and served with different garnishes.
Puree is a thick soup made from first or second stock. The thickening may be either meat, game, or vegetables, the substance with which it has been thickened being first rubbed through a sieve.
Stock may be made in a proper stock pot, or in a large goblet. The stock pot should receive all scraps of meat and vegetables that are over from the preparation of other dishes; also any meat boilings. A sufficient quantity of fresh cold water must always be added, and a little salt to throw up the scum.
A stock pot should be kept slowly boiling, gradually concentrating its contents, and should not stand by the side of the fire in a lukewarm condition. Skim the stock thoroughly once or twice. A few washed egg-shells put into the stock-will help to clear it. One whole day is sufficient to boil stock; then strain thoroughly, wash the pan, and set it outside to air. These precautions are necessary to prevent the stock becoming sour from fermentation.
The bones and any pieces of the meat may be put on next day with any fresh scraps. The vegetables are useless once the flavour has all been extracted.
Stock and soup should never be allowed to cool in the saucepan, but should be poured into basins and left uncovered. The grease that rises to the top should not be removed before the soup is used, as the covering of fat helps to preserve it.
If the stock has to be kept some time, it is best preserved by putting into a saucepan and bringing it to the boil each day.
The next variety of soup is that which is made on the lines of a good Scotch broth, of meat and vegetables, either boiled in stock or in water. This is known in France as pot-au-feu, and here the boiled meat is intended to be eaten with or immediately after the soup.
Grand bouillon is a stronger extract than pot-au-feu. In this, to the meat and vegetables are added bones and connective tissue for the sake of the gelatine. This, when cold and strained, forms a slightly firm jelly, which can be cleared and flavoured in many ways. (This variety is usually "clear soup.") If an extract sufficiently strong to be termed grand bouillon be taken, and to this is added extract or puree of roast meat, fowl, or vegetable, the result is known as a consomme. This form of soup is the most nutritious, because it contains most albumin.
In framing a diet, due weight must always be given to the composition of the particular soup to be taken.