The Flesh of Birds contains very little fat, and that found separate from the meat is rarely nice. Most birds are edible, but fish-eating birds are apt to be nasty. As a rule, the flavour of the male bird is richer than that of the female. The chief virtues in poultry are their tenderness, and the large proportion of phosphates they contain. They are deficient in fat and in iron. To compensate for the former, one commonly takes with them melted butter and fat bacon or pork sausages; to compensate for the latter, the addition of Liebig’s extract to the gravy is useful. Young, and consequently tender, birds are known by their large feet and leg-joints. When a bird appears at table with violet-tinged thighs and a thin neck, if possible avoid being helped to the leg. Wild fowls are harder and less digestible than tame. In ducks and geese fat is more abundant, and of a stronger flavour; they are, consequently, not so digestible as fowls.
Fish forms an important article of diet. It is easily cooked, and usually very digestible; it possesses a larger bulk in proportion to its nutritive quality, and hence is very valuable for those who habitually take an excess of meat food, which is commonly the case with those leading sedentary lives, and in declining years. There appears to be no foundation for the statement that fish is rich in phosphorus, and is thus a good brain food. Generally, white-fleshed fish is more digestible than red-fleshed (such as salmon), the latter usually containing more fat than the former. When the fat is distributed throughout the flesh, as in the salmon, fish is more satisfying than when it is mainly stored up in the liver, as in the cod-fish. According to Payen, the percentage proportion of fat in soles is only 0.248, in whiting 0.383, conger eel 5.021, mackerel 5.758, eels 23.861. The addition of some fatty food, as melted butter, is very advisable to such meats as poultry, rabbits, soles, whiting, plaice, haddock, cod, turbot, and other fishes; whereas sprats, eels,. herrings, pilchards, salmon, etc., are more or less rich in fat.
A Hen’s Egg usually weighs a little under two ounces. It consists of 74 per cent. of water and 26 per cent. of solid matter. The white of the egg is chiefly albumin, the yolk consists of a very digestible oil, rich in phosphorus and iron, each particle of the oil being enveloped in a form of albumin called vitellin. The salts are chiefly contained in the shell. There is no sugar in the egg, the necessity for such oxidisable material for the chick being obviated by the heat produced by incubation. Eggs, when kept for some time, lose weight, owing to evaporation through the porous shell; similarly, air entering from without sets up decomposition. In a solution of brine containing an ounce of common salt to half a pint of water, fresh eggs sink, stale ones float; rotten eggs may even float in fresh water. Eggs may be preserved by keeping them in brine, or, better still in lime water, or by smearing them over with lard or butter, as soon as possible after they are laid.
Cow’s Milk has a specific gravity of 1028-34, and on allowing it to stand in a long narrow vessel ought to form ten or twelve per cent. of its volume of cream. The percentage composition of human and cow’s milk has been given on page [5]. The legal minimum standard for dairy milk, which is presumably derived from a number of cows, is now 3 per cent. of fat, and 8.5 per cent. of “solids not fat.” This standard is unfortunately very low, and allows a considerable margin of adulteration, which cannot be prevented by legal means. Thus ordinary milk derived from a herd of cows would probably contain 4.5 per cent. of fat; and it is, therefore, practicable to mix pure new milk with a large proportion of separated milk, and yet keep within the legal standard. This is largely done in towns, and infants suffer much from the deficiency of cream in their sole food (see page [28]). The lactometer determines the specific gravity, which should be taken at a temperature of 60° F. In skimmed or separated milk it will be over 1034; watering on the contrary lowers the specific gravity. If the milk has been both watered and skimmed the specific gravity will give an uncertain indication. Measurement of the cream in a tall narrow glass will enable one to detect the second possible source of fallacy; but the composition of milk can only be certainly determined by analysis. This is done (a) by evaporating a weighed amount of milk to dryness and then re-weighing. (b) From a separate amount of dried milk the fat is extracted by ether, the ether then evaporated, the remaining fat weighed, and its percentage calculated. The weight of fat deducted from the total solids i.e. (b) from (a), gives the “solids not fat.” The following example will make the method then followed clear. The sample gives 7.9 per cent. of “solids not fat.” Genuine milk contains at least 8.5 per cent. of “solids not fat.”
Then the sample contains—
100 × 7.9 ∕ 8.5 = 92.9 per cent. of genuine milk,
i.e. 7.1 per cent. of water has been added to it.
Half a pint of milk supplies as much nitrogenous nutriment as two good-sized eggs, and as three and a half ounces of beef. Milk may be deteriorated (1) by skimming or “separating” by machinery, or (2) by the addition of water—the first diminishing the proportion of fats, and the second the total amount of solids.
Skim Milk still contains nearly 1 per cent. of fat, but Separated Milk, in which the cream has been removed by centrifugal apparatus, contains less than 1 ∕ 8 per cent.
Skim or separated milk forms a cheap source of nitrogenous food; but when it is sold mixed with new or alone as new milk, the public is defrauded, and infants fed on it are robbed of the fat which is so essential for their growth.
Condensed Milk is milk deprived of a large part of its water. It represents three times its volume of fresh milk. There are in the market (a) unsweetened and condensed whole milk, (b) sweetened and condensed whole milk, and (c) sweetened and condensed skim or separated milk. Unfortunately the latter is most largely sold because cheapest; and infants are thus often robbed of fat, a most important element in their food. Always examine the label of each tin carefully, to ascertain whether the milk has been deprived of its cream. The law requires that this fact should be stated on the label. Tins which have bulged should be rejected. Condensed milk is more easily digested by infants than new cow’s milk, but it lacks the anti-scorbutic properties of new milk (see page 28). Even the condensed whole milk if diluted beyond 1 part of milk to 3 of water is deficient in fat. Sweetened condensed milk has one-third its weight of extraneous sugar added to it, and on this account it tends in children to produce fatness, and a distaste for simple food; in children fed on it alone ossification (formation of bone) is retarded, and resistance to illness is diminished. The only dietetic advantages it possesses over fresh cow’s milk are its freedom from possible disease germs and easier digestibility.