The Three Great Classes Of Food-fuel


Categories: THE COAL FOODS
Sources: A Handbook Of Health

Food is Fuel. Now what is the chief quality which makes one kind of

food preferable to another? As our body machine runs entirely upon the

energy or strength which it gets out of its food, a good food must

have plenty of fuel value; that is to say, it must be capable of

burning and giving off heat and steaming-power. Other things being

equal, the more it has of this fuel value, the more desirable and

valuable it will be as a food.



From this point of view, foods may be roughly classified, after the

fashion of the materials needed to build a fire in a grate or stove, as

Coal foods, Kindling foods, and Paper foods. Although coal, kindling,

and paper are of very different fuel values, they are all necessary to

start the fire in the grate and to keep it burning properly. Moreover,

any one of them would keep a fire going alone, after a fashion, provided

that you had a grate or furnace large enough to burn it in, and could

shovel it in fast enough; and the same is true, to a certain degree, of

the foods in the body.



How to Judge the Fuel Value of Foods. One of the best ways of roughly

determining whether a given food belongs in the Coal, the Kindling, or

the Paper class, is to take a handful or spoonful of it, dry it

thoroughly by some means,--evaporating, or driving off the water,--and

then throw what is left into a fire and see how it will burn. A piece of

beef, for instance, would shrink a good deal in drying; but about

one-third of it would be left, and this dried beef would burn quite

briskly and would last for some time in the fire. A piece of bread of

the same size would not shrink so much, but would lose about the same

proportion of its weight; and it also would burn with a clear, hot

flame, though not quite so long as the beef. A piece of fat of the same

size would shrink very little in drying and would burn with a bright,

hot flame, nearly twice as long as either the beef or the bread. These

would all be classed as Coal foods.



Then if we were to dry a slice of apple, it would shrink down into a

little leathery shaving; and this, when thrown into the fire, would burn

with a smudgy kind of flame, give off very little heat, and soon

smoulder away. A piece of raw potato of the same size would shrink even

more, but would give a hotter and cleaner flame. A leaf of cabbage, or a

piece of beet-root, or four or five large strawberries would shrivel

away in the drying almost to nothing and, if thoroughly dried, would

disappear in a flash when thrown on the fire. These, then, except the

potato, we should regard as Kindling foods.



But it would take a large handful of lettuce leaves, or a big cup of

beef-tea, or a good-sized bowl of soup, or a big cucumber, or a gallon

of tea or coffee, to leave sufficient solid remains when completely

dried, to make more than a flash when thrown into the fire. These, then,

are Paper foods, with little fuel value.





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