Denaturation time and temperature effects on solubility, tensile properties, and oxygen permeability of whey protein edible films

Whey protein film solubility decreased as film-forming solution heating time and temperature increased. No differences were observed in solubility between films soaked in water at 25 degreesC for 24 h and 100 degreesC for 4 min. However, the degree of swelling was significantly larger for films soaked at 100 degreesC. Films became stiffer, stronger and more stretchable as film-forming solution time and temperature were increased. Oxygen permeability (OP) was lower for films made from heat-denatured whey protein than for films made from native whey protein. Results suggest that an increase in covalent cross-linking, as heat denaturation of the whey protein increases, is accountable for film water insolubility, higher tensile properties and lower OP.