Source

Gelatin is a nitrogenous food classed with proteins, under the division called gelatinoids or albuminoids, and derived from "collagen," the chief constituent of connective tissue with its various modifications, as tendons, "chondri-gen" of cartilage, or the "ossein" of bone. "By proper treatment, any form of connective tissue can be made to yield gelatin. Hide clippings yield glue, a crude form of gelatin, and much commercial gelatin is simply a purified glue, derived from such a source. Isinglass, obtained from the swimming bladder of the sturgeon and other fish, is the purest form of gelatin; the gelatin obtained from calves' feet is also of high quality."1

General Principles In Cooking

Gelatin is insoluble in cold water, but when allowed to stand in it will swell from absorption of water. "Gelatin is very soluble in boiling water, and on cooling sets into a jelly. This jellying will occur in a solution containing as little as 1 per cent. of gelatin."1 Gelatin is decomposed by boiling and consequently if allowed to boil will not solidify on cooling.

Digestibility

Gelatin is very easily digested in the stomach, and readily absorbed from the small intestines.

Nutritive Value

Although gelatin is a protein food, it cannot alone support life. Proteins are made up of groups of amino acids, most of which it seems necessary to have represented in the diet, to secure complete repair of the waste of nitrogenous tissue. In gelatin two important acids are lacking; hence not more than two-thirds of the day's nitrogen requirement should be given in the form of gelatin. Because it can to this extent take the place of other proteins, gelatin has often been called a "protein-sparer," rather than a true protein. In the ordinary intake of animal food, not more than one-eighth of the total nitrogen is in the form of gelatin. It is usually not convenient to take more than 25 to 30 grams (about 1 ounce) in a day. Six ounces of calf's foot jelly (which would be a large helping) contain less than half an ounce of gelatin. Jellying will occur in a solution containing as little as 1 per cent. of gelatin. Gelatin has the advantage (along with other proteins) of fixing a good deal of acid in the process of stomach digestion and is thus of service in cases of hyperacidity of the stomach, when given in other forms than acid jellies. It seems also to promote the secretion of gastric juice. It is useful in febrile states as it really belongs with liquid foods, melting as it does at body temperature.

1 State of Connecticut. Report of The Connecticut Agricultural Experiment Station. Pood and Drug Products, 1909. Being Part II of the Biennial Report of 1909-1910.

In convalescence, acid jellies (orange, lemon, etc.,) are of service as a pleasant supplement to the ordinary diet, but the actual nutriment which they supply is small.

Extra nutriment can be added to gelatin by combining it with eggs and milk, as in Snow Pudding, Charlottes of various kinds, Spanish Cream, etc., all of which are attractive forms of invalid diet.

Meat Jellies are condensed form of broth, and are prepared by taking any meat containing a large proportion of connective tissues and cooking long and slowly. (Note broths, page 217 for directions and recipes.) Home-made jellies, properly prepared, have a pleasing flavor and are an agreeable addition to diet of an invalid, although their nutritive value is low.