Below 35 to 40 °C gelatin swells and absorbs approximately 5 to 10 times its weight of water to form a gel. Gelatin is soluble in glycerol and acetic acid, and more soluble in hot than in cold water. It is practically insoluble in most organic solvents such as alcohol, chloroform, carbon disulphide, carbon tetrachloride, ether, benzene, acetone and oils. Sterile solutions of gelatin stored cold are stable indefinitely, but at elevated temperatures hydrolysis or rupture of peptide bonds occurs, increasing the number of free amino groups. Gel strength and viscosity gradually weaken upon prolonged heating in solution above ~40 °C; this degradation is accelerated by extremes in pH, proteolytic enzymes and bacterial action.

• Type A gelatin derived from acid hydrolysed tissue

Type: A (acid hydrolysis from collagen). Bloom: The water binding capacity of the gelatin. The higher the bloom number, the higher the water binding capacity. Tested by preparing a 6% gel in a gelometer, which punches a plunger through the gel testing for the gel strength (the higher the strength of the gel, the higher the bloom number). The bloom number is also proportional to the average molecular weight ranging from 20000 to 100000.

Gelatin is a heterogeneous mixture of water-soluble proteins of high average molecular weights, present in collagen. The proteins are extracted by boiling skin, tendons, ligaments, bones, etc. in water. Type A gelatin is derived from acid hydrolysed tissue. The charge on a gelatin molecule and its isoelectric point are primarily due to the carboxyl amino and guanidino groups on the side chains. Type A gelatin has 78 to 80 millimoles of free carboxyl groups per 100 g of protein and a pI of 7,0 to 9,0.

Gelatin is used as a stabiliser, thickener and texturizer in foods; to inhibit crystallisation in bacteriology and prepare cultures; in PCR hybridisation in molecular biology; in the pharmaceutical industry as a suspending agent, encapsulating agent and tablet binder; and in veterinary applications as a plasma expander and hemostatic sponge.