Kosher gelatin is obtained from collagen found in the hides of kosher slaughtered cattle.
Native collagen is a scleroprotein based on a polypeptide chain comprised of more than 1,000 amino acids. Three of these chains form a triple helix. Groups of triple helices produces fibrils of collagen stabilized by cross-linking, forming a 3-dimensional network structure that is insoluble. Collagen is converted to a soluble form by through enzymatic hydrolysis. Carefully controlled partial hydrolysis yields gelatin, while complete enzymatic hydrolysis as produces gelatin hydrolysate.
Chromatographic analysis indicates that gelatin products are made of peptides. Gelatin hydrolysate contains many small peptides and exhibit molecular weights between 500 and 15,000, with an average value of about 3,000.
Gelatin consists of much larger peptides with molecular weight up to several hundred thousand.
The amino acid content of collagen, and hence of gelatin and gelatin hydrolysate, is very specific, with about one third glycine and 22% proline and its hydroxylated form, hydroxyproline.Commercially available edible gelatin has the following composition:
Gelatin is missing only two amino acids; cysteine and tryptophan. Because tryptophan is an essential amino acid, however, gelatin is considered an incomplete protein.