ABSTRACT
COLLAGEN is an abundant protein constituent of connective tissue in verte-brate (about 50% of total human protein) and invertebrate animals (Johnston-Banks, 1990). Similar to cellulose in plants, collagen molecules support mechanical stresses transferred to them by a low-modulus matrix (Yannas, 1972). Thermal or chemical dissociation of collagen polypeptide chains forms products known as gelatin. Insoluble collagen is converted to soluble gelatin by acid or alkaline/lime (mild and slow) processing. Two processes are mainly used for commercial production of gelatin. In the first process, the collagen in hide or demineralized bone is partly depolymerized by prolonged liming that breaks down covalent cross-links. The occurring hydrolysis results in extensive release of collagenous material, which is solubilized at near neutral pH at temperatures of 60-90 C (Type B gelatin). The acid process (Type A gelatin) involves soaking skin or bone in a dilute acid followed by extraction at acid pH. Gelatin manufacturing has been discussed extensively (Robinson, 1953; Rose, 1987; Johnston-Banks, 1990; GMIA, 1993).
