Grease resistance and mechanical properties of isolated soy protein‐coated paper

Abstract

Abstract Grease‐resistant paper has been produced by coating paper with isolated soy protein (ISP). Tensile strength (TS) of ISP‐coated paper is 28–30 MPa (between the TS of paper and of ISP film). TS of the ISP‐coated paper (2.3 kg/ream) was highest (36.0 MPa) among other ISP‐coated papers, but elongation (E) of the papers seemed to decrease (though not statistically significantly) as the thickness of the ISP coating increased. ISP‐coated papers were highly impermeable to grease penetration for the first 2 h of the test. The percent stained area of two commercially used polyethylene‐laminated papers was higher than those of ISP‐coated papers. As the amount of plasticizer (a mixture of glycerol and polyethylene glycol) was increased in ISP‐coated paper, the TS decreased and the E increased. When tested, the percent stained areas of the paper containing 0.6 and 1.0 g plasticizer/g protein were lower for the first 2 h than those of the papers containing 0.0 and 0.2 g plasticizer/g protein. Also, percent stained area increased with time. Grease resistance of papers coated with ISP at levels higher than 2.0 kg/ream was equal to or lower than that of polyethylene laminates used for quick‐service restaurant sandwich packaging.