Diffusions of lysozyme (LZ) in whey protein isolate (WPI) films and in smoked salmon coated with LZ-incorporated WPI films (LZ-WPI films) were investigated. Diffusion and partition coefficients for the diffusion for LZ at 4 degrees C in smoked salmon coated with a LZ-WPI film (WPI:glycerol = 1: 1) were determined by fitting mathematical models to the experimental data. Diffusion coefficients for LZ in films were further determined with LZ-WPI films, prepared with different WPI-glycerol ratios (1: 1, 2: 1, and 3: 1) and stored at 4, 10 and 22 degrees C. The diffusion coefficients for the LZ diffusion in the film (WPI:glycerol = 1:1) and in the salmon at 4 degrees C and the partition coefficient (K-12) were 9.8 +/- 0.8 x 10(-14) m(2)/s, 4.8 +/- 3.9 x 10(-11) m(2)/s, and 0.4 +/- 0.2, respectively. The diffusion coefficients for the LZ diffusion in the films (D-1) with the different WPI-glycerol ratios and storage temperatures were in the range of 2.5 x 10(-16) -3.4 x 10(-13) m(2)/s. The D-1 decreased as the WPI-glycerol ratio increased or storage temperature decreased. The E, values for diffusion in 1: 1, 2: 1, and 3:1 WPI:glycerol films were 16.3, 27.4, and 63.9 kJ/mol, respectively. (C) 2007 Elsevier Ltd. All rights reserved.