The effect of protein, sorbitol, beeswax and potassium sorbate concentrations in whey protein films on their ultimate tensile strength, Young's modulus. elongation and transparency was investigated using mixture response surface methods. Protein, sorbitol and potassium sorbate were important factors influencing ultimate tensile strength, Young's modulus and elongation. Beeswax did not have an impact on ultimate tensile strength and Young's modulus, and it had little effect on elongation. On the other hand, it was the primary factor affecting the transparency of the films. Mixture proportions of protein = 0.58, sorbitol = 0.38, beeswax = 0 and potassium sorbate = 0.04 would yield an edible film with transparency >= 89%, ultimate tensile strength >= 4 MPa, elongation >= 40% and Young's modulus <= 190 MPa. (C) 2007 Elsevier Ltd. All rights reserved.