Gelatin, nutritive value

Gelatin is made from collagen, which is a structural protein composed primarily of glycine, proline, and hydroxyproline. As a result, gelatin has low nutritional value because it lacks many of the essential amino acids. 

From the differences observed in the products of hydrolysis of the various albuminoids, can we draw any practical conclusions as to the nutritive value of these same proteins In particular, as regards gelatin, which cannot be regarded as an albuminoid food properly speaking, should we seek the cause of its nondigestibility in the excess of glycin formed, or in the relatively... 

Although gelatin is 98-99% protein by dry weight, it has less nutritional value than many other complete protein sources. Gelatin is unusually high in the nonessential amino acids glycine and proline (i.e., those produced by the human body) while lacking certain essential amino acids (i.e., those not produced by the human body). It contains no tryptophan and is deficient in isoleucine, threonine, and methionine. 

Ash content is a measure of total minerals and is a reliable index of nutritional value for many foods (tea, flour, edible gelatin, etc.) and feed (for poultry and cattle) and is recognized as a useful tool in determining the nature and distribution of mineral constituents of food. Ash is the inorganic material left after complete oxidation of organic material at high temperatures (500-600°C). 

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