Human Foods and Their Nutritive Value | Page 5

Some of the
elements, as phosphorus and sulphur, are in organic combination with
the nitrogenous compounds, as the nucleated albuminoids, which are
very essential for animal life. In both plant and animal bodies, the
mineral matter is present as mineral salts and organic combinations. It
is held that the ash elements which are in organic combination are the
forms mainly utilized for tissue construction. While it is not known just
what part all the mineral elements take in animal nutrition, experiments
show that in all ordinary mixed rations the amount of the different
mineral elements is in excess of the demands of the body, and it is only
in rare instances, as in cases of restricted diet, or convalescence from
some disease, that special attention need be given to increasing the
mineral content of the ration. An excess of mineral matter in foods is
equally as objectionable as a scant amount, elimination of the excess
entailing additional work on the body.
The composition of the ash of different food materials varies widely,
both in amount, and form of the individual elements. When for any
reason it is necessary to increase the phosphates in a ration, milk and
eggs do this to a greater extent than almost any other foods. Common
salt, or sodium chloride, is one of the most essential of the mineral
constituents of the body. It is necessary for giving the blood its normal
composition, furnishing acid and basic constituents for the production
of the digestive fluids, and for the nutrition of the cells. While salt is a
necessary food, in large amounts, as when the attempt is made to use
sea water as a beverage, it acts as a poison, suggesting that a material
may be both a food and a poison. When sodium chloride is entirely
withheld from an animal, death from salt starvation ensues. Many foods
contain naturally small amounts of sodium chloride.

4. Organic Matter.--That portion of a food material which is converted
into gaseous or volatile products during combustion is called the
organic matter. It is a mechanical mixture of compounds made up of
carbon, hydrogen, oxygen, nitrogen, and sulphur, and is composed of
various individual organic compounds, as cellulose, starch, sugar,
albumin, and fat. The amount in a food is determined by subtracting the
ash and water from 100. The organic matter varies widely in
composition; in some foods it is largely starch, as in potatoes and rice,
while in others, as forage crops consumed by animals, cellulose
predominates. The nature of the prevailing organic compound, as sugar
or starch, determines the nutritive value of a food. Each has a definite
chemical composition capable of being expressed by a formula.
Considered collectively, the organic compounds are termed organic
matter. When burned, the organic compounds are converted into gases,
the carbon uniting with the oxygen of the air to form carbon dioxide,
hydrogen to form water, sulphur to form sulphur dioxide, and the
nitrogen to form oxides of nitrogen and ammonia.
5. Classification of Organic Compounds.--All food materials are
composed of a large number of organic compounds. For purposes of
study these are divided into classes. The element nitrogen is taken as
the basis of the division. Compounds which contain this element are
called nitrogenous, while those from which it is absent are called
non-nitrogenous.[2] The nitrogenous organic compounds are composed
of the elements nitrogen, hydrogen, carbon, oxygen, and sulphur, while
the non-nitrogenous compounds are composed of carbon, hydrogen,
and oxygen. In vegetable foods the non-nitrogenous compounds
predominate, there being usually from six to twelve parts of
non-nitrogenous to every one part of nitrogenous, while in animal
foods the nitrogenous compounds are present in larger amount.
NON-NITROGENOUS COMPOUNDS
6. Occurrence.--The non-nitrogenous compounds of foods consist
mainly of cellulose, starch, sugar, and fat. For purposes of study, they
are divided into subdivisions, as carbohydrates, pectose substances or
jellies, fats, organic acids, essential oils, and mixed compounds. In

plants the carbohydrates predominate, while in animal tissue the fats
are the chief non-nitrogenous constituents.
7. Carbohydrates.--This term is applied to a class of compounds similar
in general composition, but differing widely in structural composition
and physical properties. Carbohydrates make up the bulk of vegetable
foods and, except in milk, are found only in traces in animal foods.
They are all represented by the general formula CH2n2n, there being
twice as many hydrogen as oxygen atoms, the hydrogen and oxygen
being present in the same proportion as in water. As a class, the
carbohydrates are neutral bodies, and, when burned, form carbon
dioxide and water.
[Illustration: FIG. 2.--CELLULAR STRUCTURE OF PLANT CELL.]
8. Cellulose is the basis of the cell structure of plants, and is found in
various physical forms in food materials.[3] Sometimes it is hard and
dense, resisting digestive action and mechanically inclosing other
nutrients and thus