Gelatin is a amphoteric protein derived from the heating of collagen. An amphoteric substance is one that can behave as an acid or a base, and gelatin can be produced either by pre-treating collagen with an acid or with a base. The various pre-treatments create two different varieties of gelatin called A and B.
Gelatin can only be produced from tissue containing Type I collagen, a kind of collagen that contains no cystine, which MedTerms states is the least soluble of all the amino acids. Although gelatin is pure animal protein, it is not considered a complete protein, as it has very low levels of methionine and absolutely no tryptophan, two essential amino acids.
FoodNetwork.com describes gelatin as a tasteless and odorless thickening agent derived from the skeletal system and connective tissues of animals. Gelatin.co.za explains that gelatin manufacturing frequently involves using animal bones and hides. The two manufacturing processes, acid or base, are used on different raw materials and produce gelatins which have slightly different chemical properties. Acidic treatment is used on pigskins and raw animal bones, and results in Type A gelatin, with a slightly higher nitrogen content, and an isoionic point between 7 and 9. Treatment with bases is done on cow skins and produces Type B, with a lower nitrogen content and an isoionic point between 4.8 and 5.2. An isoionic point is the pH at which all ions except for oxygen and hydrogen are removed from a substance.