We may define a food to be any substance which will repair the functional
waste of the body, increase its growth, or maintain the heat, muscular,
and nervous energy. In its most comprehensive sense, the oxygen of the air
is a food; as although it is admitted by the lungs, it passes into the
blood, and there re-acts upon the other food which has passed through the
stomach. It is usual, however, to restrict the term food to such nutriment
as enters the body by the intestinal canal. Water is often spoken of as
being distinct from food, but for this there is no sufficient reason.
Many popular writers have divided foods into flesh-formers, heat-givers,
and bone-formers. Although attractive from its simplicity, this
classification will not bear criticism. Flesh-formers are also
heat-givers. Only a portion of the mineral matter goes to form bone.
Class I.--INORGANIC COMPOUNDS.
Sub-class 1. Water. 2. Mineral Matter or Salts.
Class II--ORGANIC COMPOUNDS.
1. Non-Nitrogeneous or Ternary Compounds. _a_ Carbohydrates.
_b_ Oils. _c_ Organic Acids.
2. Nitrogenous Compounds. _a_ Proteids. _b_ Osseids.
Class III.--NON-NUTRITIVES, FOOD ADJUNCTS AND DRUGS.
Essential Oils, Alkaloids, Extractives, Alcohol, &c.
These last are not strictly foods, if we keep to the definition already
given; but they are consumed with the true foods or nutrients, comprised
in the other two classes, and cannot well be excluded from consideration.
Water forms an essential part of all the tissues of the body. It is the
solvent and carrier of other substances.
Mineral Matter or Salts, is left as an ash when food is thoroughly
burnt. The most important salts are calcium phosphate, carbonate and
fluoride, sodium chloride, potassium phosphate and chloride, and compounds
of magnesium, iron and silicon.
Mineral matter is quite as necessary for plant as for animal life, and is
therefore present in all food, except in the case of some highly-prepared
ones, such as sugar, starch and oil. Children require a good proportion of
calcium phosphate for the growth of their bones, whilst adults require
less. The outer part of the grain of cereals is the richest in mineral
constituents, white flour and rice are deficient. Wheatmeal and oatmeal
are especially recommended for the quantity of phosphates and other salts
contained in them. Mineral matter is necessary not only for the bones but
for every tissue of the body.
When haricots are cooked, the liquid is often thrown away, and the beans
served nearly dry, or with parsley or other sauce. Not only is the food
less tasty but important saline constituents are lost. The author has made
the following experiments:--German whole lentils, Egyptian split red
lentils and medium haricot beans were soaked all night (16 hours) in just
sufficient cold water to keep them covered. The water was poured off and
evaporated, the residue heated in the steam-oven to perfect dryness and
weighed. After pouring off the water, the haricots were boiled in more
water until thoroughly cooked, the liquid being kept as low as possible.
The liquid was poured off as clear as possible, from the haricots,
evaporated and dried. The ash was taken in each case, and the alkalinity
of the water-soluble ash was calculated as potash (K_{2}O). The quantity
of water which could be poured off was with the German lentils, half as
much more than the original weight of the pulse; not quite as much could
be poured off the others.
G. Lentils. E. Lentils. Haricots. Cooked H.
Proportion of liquid 1.5 1.25 1.20 --
Soluble dry matter 0.97 3.38 1.43 7.66 per cent.
Ash 0.16 0.40 0.28 1.26 " "
Alkalinity as K_{2}O 0.02 0.082 0.084 0.21 " "
The loss on soaking in cold water, unless the water is preserved, is seen
to be considerable. The split lentils, having had the protecting skin
removed, lose most. In every case the ash contained a good deal of
phosphate and lime. Potatoes are rich in important potash salts; by
boiling a large quantity is lost, by steaming less and by baking in the
skins, scarcely any. The flavour is also much better after baking.
The usual addition of common salt (sodium-chloride) to boiled potatoes is
no proper substitute for the loss of their natural saline constituents.
Natural and properly cooked foods are so rich in sodium chloride and other
salts that the addition of common salt is unnecessary. An excess of the
latter excites thirst and spoils the natural flavour of the food. It is
the custom, especially in restaurants, to add a large quantity of salt to
pulse, savoury food, potatoes and soups. Bakers' brown bread is usually
very salt, and sometimes white is also. In some persons much salt causes
irritation of the skin, and the writer has knowledge of the salt food of
vegetarian restaurants causing or increasing dandruff. As a rule, fondness
for salt is an acquired taste, and after its discontinuance for a time,
food thus flavoured becomes unpalatable.
Organic Compounds are formed by living organisms (a few can also be
produced by chemical means). They are entirely decomposed by combustion.
The Non-Nitrogenous Organic Compounds are commonly called carbon
compounds or heat-producers, but these terms are also descriptive of the
nitrogenous compounds. These contain carbon, hydrogen and oxygen only, and
furnish by their oxidation or combustion in the body the necessary heat,
muscular and nervous energy. The final product of their combustion is
water and carbon dioxide (carbonic acid gas).
The Carbohydrates comprise starch, sugar, gum, mucilage, pectose,
glycogen, &c.; cellulose and woody fibre are carbohydrates, but are little
capable of digestion. They contain hydrogen and oxygen in the proportion
to form water, the carbon alone being available to produce heat by
combustion. Starch is the most widely distributed food. It is insoluble in
water, but when cooked is readily digested and absorbed by the body.
Starch is readily converted into sugar, whether in plants or animals,
during digestion. There are many kinds of sugar, such as grape, cane and
milk sugars.
The Oils and Fats consist of the same elements as the carbohydrates,
but the hydrogen is in larger quantity than is necessary to form water,
and this surplus is available for the production of energy. During their
combustion in the body they produce nearly two-and-a-quarter times (4 :
8.9 = 2.225) as much heat as the carbohydrates; but if eaten in more than
small quantities, they are not easily digested, a portion passing away by
the intestines. The fat in the body is not solely dependent upon the
quantity consumed as food, as an animal may become quite fat on food
containing none. A moderate quantity favours digestion and the bodily
health. In cold weather more should be taken. In the Arctic regions the
Esquimaux consume enormous quantities. Nuts are generally rich in oil.
Oatmeal contains more than any of the other cereals (27 analyses gave from
8 to 12.3 per cent.)
The most esteemed and dearest oil is Almond. What is called Peach-kernel
oil (Oleum Amygdalæ Persicæ), but which in commerce includes the oil
obtained from plum and apricot stones, is almost as tasteless and useful,
whilst it is considerably cheaper. It is a very agreeable and useful food.
It is often added to, as an adulterant, or substituted for the true Almond
oil. The best qualities of Olive oil are much esteemed, though they are
not as agreeable to English taste as the oil previously mentioned. The
best qualities are termed Virgin, Extra Sublime and Sublime. Any that has
been exposed for more than a short time to the light and heat of a shop
window should be rejected, as the flavour is affected. It should be kept
in a cool place. Not only does it vary much in freedom from acid and
rancidity, but is frequently adulterated. Two other cheaper oils deserve
mention. The "cold-drawn" Arachis oil (pea-nut or earth-nut oil) has a
pleasant flavour, resembling that of kidney beans. The "cold-drawn" Sesamé
oil has an agreeable taste, and is considered equal to Olive oil for
edible purposes. The best qualities are rather difficult to obtain; those
usually 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.
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