Diffusion of the antimicrobial lysozyme from a whey protein coating on smoked salmon

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 °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 °C. The diffusion coefficients for the LZ diffusion in the film (WPI:glycerol = 1:1) and in the salmon at 4 °C and the partition coefficient (K12) were 9.8 ± 0.8 × 10−14 m2/s, 4.8 ± 3.9 × 10−11 m2/s, and 0.4 ± 0.2, respectively. The diffusion coefficients for the LZ diffusion in the films (D1) with the different WPI–glycerol ratios and storage temperatures were in the range of 2.5 × 10−16–3.4 × 10−13 m2/s. The D1 decreased as the WPI–glycerol ratio increased or storage temperature decreased. The Ea 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.