Digestibility Of Meats And Fats
( Originally Published 1917 )
There is much error in the popular mind as to what constitutes digestibility of food: In general any food is said to be digestible which, even when eaten in large quantities, does not occasion pain and suffering, or cause a feeling of fulness after eating. A more scientific test is that which tells the length of time that the food remains in the stomach or in the digestive tube; or rather the length of time necessary for the complete digestion of such and such an article in such and such quantities. But the most accurate method of expressing the digestibility of an article of food is to tell in what proportion it is absorbed by the digestive tube.
Every one admits that roast meat is more digestible than raw meat or boiled meat. Poultry or roast veal, the so-called white meats, are said to be very easily digested, and are consequently selected for invalids. These differences are doubtless due to the greater or less delicacy of the muscular fibres which offer a varying resistance to the digestive juices; and also to the quantity and nature of the fat which pertains to each sort of meat.
This last point is very important; we are accustomed to say that the digestion of fat in a healthy person is in general good. But it can be shown that a ration of a few ounces of fat in 24 hours represents an accomplishment which is hardly performed by those living in northern countries, yet experiment shows that the digestive tube is capable of absorbing consider-ably larger quantities. Thus in one series of tests it was found that of three ounces of butter, all but six grains were absorbed, but the results with other fats were not so good. Of the fat of mutton, which does not melt at so low a point as does butter, about 10 per cent. did not absorb. But liquid fats, such as olive oil, which are kept as liquids by the heat of the body, were wholly digested.
In general the stomach seems to experience a sort of antipathy to fats, and there is a tendency to arrest digestion by using them. We are all able to tell the effect upon ourselves and upon our digestions by the foods which are very rich in fats, and especially those of fish, which are fatter than others.
It is probable that fat plays a great part in giving to the several kinds of meat their distinctive taste. This is a point to be borne in mind in frying, as the fat used is very likely to impart its flavor to the food which is cooked in it.
THE NUTRITIVE VALUE OF BOUILLON AND OF MEAT EXTRACT
A quantity of bouillon made in the ordinary way, without completely destroying the boiled meat, contains approximately the following matter: Albumen, .3 to .4 per cent. Gelatine, .3 to .6 per cent. Fat, .5 to 1 per cent. Salts (natural and added), 1.3 to 1.5 per cent. Ex-tractive matter, .6 to .7 per cent. .Water, 95.5 to 97 per cent.
Much of the albumen of the meat rises to the top as foam and is removed. Only a small quantity of the albumen dissolves in the liquid, on account of the natural acid which is present in the meat.
The gelatine is present in a quantity less than 10 per cent., which proportion causes liquid to congeal on cooling. A bouillon which would so congeal is not at all desirable.
The fat varies according to the nature of the meat used. Very fat bouillon may contain from 3.3 to 4 per cent. of fat, but such quantities are usually repugnant and are not easily borne by persons with weak stomachs..
It is safe to say that the quantities of albumen and fat supplied by a portion of bouillon are about the same as those yielded by two or three spoonfuls of cow's milk.
The nutritive value of bouillon is, therefore, weak, as is also that of meat extracts, which are only bouillon evaporated to dryness, or a semi-solid state, but their agreeable taste and stimulating effect render them useful adjuncts to the art of cooking.
It is a very wrong idea, maintained by many people, and even by many physicians, that meat extracts contain the nourishment and food value of a large quantity of meat; they do nothing of the kind, else albumen, fats, and other food sub-stances would be present in large proportions, and chemical analysis shows this to be far from the truth. Bouillon and solutions of meat ex-tract contain these substances in extremely _small quantities, hence the nutritive value of bouillon is very slight, and that of meat extracts, or so-called condensed meat, is often still less.
From what has been said it must not be hastily concluded that bouillon is of no use or value whatever. While a healthy person finds in it only a very small portion of what he needs, to the invalid or , convalescent, to whom the smallest quantity of nourishment that can be borne is a blessing, bouillon is one of the most useful forms to supply to a worn-out and impaired system a first food; agreeable, easy to digest, and one which possesses wonderful stimulating properties. This last property cannot be emphasized too strongly. It ex-plains the marvellous effect produced by a quantity of bouillon taken after a march or pro-longed fast. The effect is undoubtedly a nervous one. It is probable that the bouillon produces a beneficent effect upon the stomach itself. Some physiologists claim that bouillon possesses the power of stimulating the secretion of pepsin, the essential agent of digestion. This explains why bouillon has become so generally and so justly appreciated.