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2006 IFT Poster Presentation (PDF)
Presentation Number: 054C-28
Diffusion of thiocyanate and hypothiocyanite in whey protein films incorporating the lactoperoxidase system
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:
Controls of L. monocytogenes, Salmonella, and Escherichia coli O157:H7 using whey protein film-coatings incorporating lactoperoxidase systems (LPOS) have been demonstrated. Determination of diffusion coefficients (D) for active products of LPOS, such as thiocyanate (SCN-) and hypothiocyanite (OSCN-), is necessary to understand their diffusion phenomena in whey protein film and to assess the ability of whey protein films to act as their carriers to improve food safety and quality.
Objectives:
The objective of this study was to determine the diffusion coefficients for SCN- and OSCN- in whey protein isolate (WPI) films.
Methods:
The D values were measured with LPOS-incorporated WPI films, prepared with different WPI:glycerol (plasticizer) ratios (1:1, 3:1, and 5:1). The WPI 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 the samples were stored at 4, 10 and 22 °C. The D values were determined by fitting the amounts of SCN- and OSCN- released from the films to mathematical models. Activation energy (Ea) values required for the diffusions in the film were calculated using the Arrhenius equation.
Results:
The D values for diffusion of SCN- and OSCN- in the WPI films were 1.9_10-13-5.2_10-12 m2/s and 1.3_10-14-6.5_10-13 m2/s, respectively. The D values decreased as the storage temperature decreased and the WPI:glycerol ratio increased. The Ea values for the diffusion in the WPI:glycerol films of 1:1, 3:1, and 5:1 were, respectively, 13.3, 29.5, and 35.6 kJ/mol for SCN- and 15.8, 30.1, and 39.9 kJ/mol for OSCN-
Significance:
The whey protein film was a useful matrix to carry SCN- and OSCN- for their antimicrobial activity on smoked salmon. The diffusions were influenced by the film formulation and, thus, the film can be formulated to achieve a desired release rate of the oxidizing products for their antimicrobial activity.