Physical properties and oil absorption of whey-protein-coated paper

Whey-protein-isolate coating on paper produced a smooth surface, which was observed by scanning; electron microscopy. Increasing coating weight decreased the breaking stress and the Young's modulus. However, the maximum breaking strain was not affected by coating weight. Tearing strength was not changed by WPI coating. The coated paper was slightly darkened with a small reduction of L value, but the a and b values were not changed significantly. WPI coating made the coated paper slightly shiny with increased gloss. Thus, with the exception of about 12% reduction in breaking stress for 10 g/m(2) coated paper, WPI coating did not change the mechanical and optical properties of the paper markedly. WPI coating significantly reduced the rate of oil contact angle decrease on paper associated with oil absorption by paper. Therefore, WPI coating improves packaging material performance of paper by increasing oil resistance without significant change of optical and mechanical properties.