Preparation and thermal stability of gelatin edible films from shark skins

Edible gelatin films based on shark skins were successfully prepared.The effect of protein concentration,glycerol content and environmental humidity on the properties of edible gelatin films was investigated.As a result,white and transparent gelatin films could be produced using shark skins.With increasing protein content of film-forming solution,elongation at break(EAB),water vapor permeability(WVP)and transparency value of films increased slightly,but no differences in tensile strength(TS)were observed.Nevertheless,TS generally decreased with increasing glycerol concentration from 10 to 70%.The thermal stability of gelatin films was analyzed using DSC.It is revealed that the mechanical properties of films were not changed and polymeric materials exist in a glassy state when water activity(Aw)<0.33.Conversely,as Aw increased above 0.44,glass transition temperature(T_g)starting point of films below 25 ℃ was observed and EAB was increased,while TS of films decreased dramatically.In the case of Aw 0.92,gelatin films even dissolved into sol.These results clearly indicate that gelatin films prepared from shark skins could only be applied in dry environment(Aw<0.44).