28-5 |
Modeling of natamycin and potassium sorbate diffusion in whey protein isolate films for application to cheddar cheese |
L. R. FRANSSEN1, T. R. Rumsey2, and J. M. Krochta1. (1) Department of Food Science and Technology, University of California, Davis, Davis, CA 95616, (2) Department of Biological and Agricultural Engineering, University of California, Davis, Davis, CA 95616 As surface-applied preservatives migrate into cheese, mold spoilage occurs on the cheese surface. By incorporating preservatives in whey protein isolate (WPI) film coatings on cheese, the preservative migration can be slowed to enhance microbial protection of cheese. By determining the preservative diffusion in films as compared to cheese, a model can be developed to predict shelf-life. Our objective was to determine the diffusion coefficients of natamycin and potassium sorbate in WPI films and in cheddar cheese and to develop a mathematical model of a preservative-containing WPI coated cheese. WPI films with WPI:glycerol plasticizer (1:1- 15:1) and 0.3% (w/w) natamycin or 1.6% (w/w dry solids) potassium sorbate were cast. Preservative diffusion in the films was measured by immersing the films in a stirred 20% glycerol solution (Aw=0.94) at 23C and measuring preservative concentration using UV spectroscopy. Diffusion coefficients were calculated using Fick’s second law. Preservative diffusion in cheddar cheese was determined by immersing cheese in a preservative-containing solution, slicing the cheese, and extracting the preservative using AOAC method 974.10 for sorbic acid in dairy products and IDF standard 140A for natamycin determination in cheese. MATLAB was used to determine the diffusion coefficients and develop the mathematical model of a coated cheese. Natamycin diffusion coefficients in WPI films were lower than potassium sorbate diffusion coefficients. Film glycerol concentration had a smaller effect on natamycin diffusion than potassium sorbate. Diffusion coefficients of preservative in WPI films were compared to those in cheddar cheese. The results indicate that natamycin has slower diffusion than potassium sorbate in WPI films making it a more effective preservative. The different diffusion coefficients are most likely due to the preservative structures. Using this data, a mathematical model of a coated cheese can be developed to predict shelf-life and allow design of the most effective preservative-containing WPI coating.
Session 28, Dairy Foods: Developments in microbiology and chemistry of cheese
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