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2006 IFT Poster Presentation (PDF)
Presentation Number: 054B-32
Lysozyme diffusion in smoked salmon coated with whey protein films
incorporating lysozyme
S. MIN1, T.R. Rumsey2, and J.M. Krochta1, 2,
1 Department of Food Science and Technology, 2
Department of Biological and Agricultural Engineering, University of
California, Davis, One Shields Avenue, Davis, CA 95616 U.S.A.
Justification:
Diffusion and partition coefficients for antimicrobials in coated foods must be determined to assess the ability of selected polymer films to act as antimicrobial carriers for improving food safety and quality.
Objectives:
The objective was to determine the diffusion and partition coefficients for lysozyme diffusion in whey protein isolate (WPI) films and smoked salmon.
Methods:
WPI films, incorporating 204 mg lysozyme/g film, with different WPI-glycerol plasticizer ratios (1:1, 2:1, 3:1) were prepared. The films (4.1 cm-dia, 0.1-mm thickness) were placed on the top surfaces of smoked salmon samples (4.1 cm-dia, 2.5-cm thickness) and stored in 95% relative humidity (RH) chambers at 4, 10, and 22 °C. The diffusion coefficients for lysozyme diffusion in the WPI films (D1) and smoked salmon (D2) and the partition coefficients between the films and smoked salmon (K12) were determined by fitting lysozyme migration data to mathematical models derived from Fick’s law. Activation energy (Ea) required for the lysozyme diffusion in the film was calculated using the Arrhenius equation.
Results:
The D1 and D2 were 3.1×10-16-2.9×10-13 m2/s and 1.2-2.6×10-10 m2/s, respectively. The D values decreased as the storage temperature decreased and the WPI:glycerol ratio increased. The Ea values for WPI films of 1:1, 2:1, and 3:1 were 16.3, 27.4, and 63.9 kJ/mol, respectively. The K12 ranged from 0.02 to 0.49.
Significance:
By increasing the time the lysozyme was held at the salmon surface (D1<<D2), the whey protein film was effective as a carrier of the antimicrobial. The whey protein film can be formulated to achieve a desired release rate. Determined D and K12 values can be used in a model to predict the time during which antimicrobials remain above a critical inhibiting concentration and, thus, to determine optimum film-coating thickness and initial concentration of lysozyme to achieve a desired shelf life.