Effect of electrostatic repulsion on barrier properties and thermal performance of gelatin films by carboxymethyl starch, and application in food cooking.

Carboxymethyl starch (CST) was introduced to improve gelatin films and its practical application as edible high-performance films for food packaging and cooking was also investigated. The gelatin films modified by carboxymethyl starch exhibited the transparent appearance, tensile strength, barrier properties (oxygen, water vapor and UV light), and thermal performance (TGA, thermal shrinkage and heat-sealing strength). Resulting from the effect of electrostatic interaction modes on the properties of films, electrostatic repulsion could surpass electrostatic attraction in improving the tensile strength, oxygen barrier property and thermal stability of the films probably due to extensive physical entanglement without aggregation. Analysis of FTIR, zeta potential, interfacial dilatational rheology, shear rheological properties, XRD, Raman, SEM and AFM suggested that hydrogen bonding and electrostatic repulsion contributed to the excellent performance. The packaged food could also be cooked with the prepared film for porridge; and the film slightly influenced the shear rheological properties of porridge and imposed little effect on the odors (Electronic-Nose) of porridge. Hence, the gelatin films modified by carboxymethyl starch could potentially work as the edible inner packaging or the edible quantitative packaging for food, offer convenience for consumers, reduce the packaging waste and avoid an extra burden on environment.