The Chemistry of Food and Nutrition | Page 4

sold being much
inferior to Peach-kernel and Olive oils. Cotton-seed oil is the cheapest
of the edible ones. Salad oil, not sold under any descriptive name, is
usually refined Cotton-seed oil, with perhaps a little Olive oil to impart
a richer flavour.

The solid fats sold as butter and lard substitutes, consist of deodorised
cocoanut oil, and they are excellent for cooking purposes. It is claimed
that biscuits, &c., made from them may be kept for a much longer
period, without showing any trace of rancidity, than if butter or lard had
been used. They are also to be had agreeably flavoured by admixture
with almond, walnut, &c., "cream."
The better quality oils are quite as wholesome as the best fresh butter,
and better than most butter as sold. Bread can be dipped into the oil, or
a little solid vegetable fat spread on it. The author prefers to pour a
little Peach-kernel oil upon some ground walnut kernels (or other
ground nuts in themselves rich in oil), mix with a knife to a suitable
consistency and spread upon the bread. Pine-kernels are very oily, and
can be used in pastry in the place of butter or lard.
Whenever oils are mentioned, without a prefix, the fixed or fatty oils
are always understood. The volatile or essential oils are a distinct class.
Occasionally, the fixed oils are called hydrocarbons, but hydrocarbon
oils are quite different and consist of carbon and hydrogen alone. Of
these, petroleum is incapable of digestion, whilst others are poisonous.
Vegetable Acids are composed of the same three elements and undergo
combustion into the same compounds as the carbohydrates. They rouse
the appetite, stimulate digestion, and finally form carbonates in
combination with the alkalies, thus increasing the alkalinity of the
blood. The chief vegetable acids are: malic acid, in the apple, pear,
cherry, &c.; citric acid, in the lemon, lime, orange, gooseberry,
cranberry, strawberry, raspberry, &c.; tartaric acid, in the grape,
pineapple, &c.
Some place these under Class III. or food adjuncts. Oxalic acid (except
when in the insoluble state of calcium oxalate), and several other acids
are poisonous.
Proteids or Albuminoids are frequently termed flesh-formers. They are
composed of nitrogen, carbon, hydrogen, oxygen, and a small quantity
of sulphur, and are extremely complex bodies. Their chief function is to
form flesh in the body; but without previously forming it, they may be
transformed into fat or merely give rise to heat. They form the essential
part of every living cell.
Proteids are excreted from the body as water, carbon dioxide, urea, uric
acid, sulphates, &c.

The principal proteids of animal origin have their corresponding
proteids in the vegetable kingdom. Some kinds, whether of animal or
vegetable origin, are more easily digested than others. They have the
same physiological value from whichever kingdom they are derived.
The Osseids comprise ossein, gelatin, cartilage, &c., from bone, skin,
and connective issue. They approach the proteids in composition, but
unlike them they cannot form flesh or fulfil the same purpose in
nutrition. Some food chemists wish to call the osseids, albuminoids;
what were formerly termed albuminoids to be always spoken of as
proteids only.
Jellies are of little use as food; not only is this because of the low
nutritive value of gelatin, but also on account of the small quantity
which is mixed with a large proportion of water.
The Vegetable Kingdom is the prime source of all organic food; water,
and to a slight extent salts, form the only food that animals can derive
directly from the inorganic kingdom. When man consumes animal
food--a sheep for example--he is only consuming a portion of the food
which that sheep obtained from grass, clover, turnips, &c. All the
proteids of the flesh once existed as proteids in the vegetables; some in
exactly the same chemical form.
Flesh contains no starch or sugar, but a small quantity of glycogen. The
fat in an animal is derived from the carbohydrates, the fats and the
proteids of the vegetables consumed. The soil that produced the
herbage, grain and roots consumed by cattle, in most cases could have
produced food capable of direct utilisation by man. By passing the
product of the soil through animals there is an enormous economic loss,
as the greater part of that food is dissipated in maintaining the life and
growth; little remains as flesh when the animal is delivered into the
hands of the butcher. Some imagine that flesh food is more easily
converted into flesh and blood in our bodies and is consequently more
valuable than similar constituents in vegetables, but such is not the case.
Fat, whether from flesh or from vegetables is digested in the same
manner. The proteids of flesh, like those of vegetables, are converted
into peptone by the digestive juices--taking the form of a