Mechanical properties of mammalian and fish gelatins based on their weight average molecular weight and molecular weight distribution

Acid porcine skin gelatins (type A), lime bone gelatins (type B) and gelatin from different cold water fish species were compared on the basis of low deformation mechanical properties, Bloom value, weight average molecular weight, molecular weight distribution and isoelectric point. The dynamic storage modulus and Bloom value for all types of gelatin increased with increasing weight average molecular weight. Type A and type B gelatins with similar weight average molecular weight exhibited different dynamic storage modulus (G′) and different Bloom values. This is most probably due to a different molecular weight distribution as well as the presence of different hydrolytic fragments. The present study suggests that it may be possible to improve the mechanical properties by removing low molecular weight molecules from a gelatin sample. The Bloom values for gelatin from haddock, saithe and cod were determined to be 200, 150 and 100 g from a linear correlation between G′ and Bloom.