Submitted to: Annual Meeting of the Institute of Food Technologists
Publication Type: Abstract Only
Publication Acceptance Date: 11/30/2004
Publication Date: 7/16/2005
Citation: Bower, C.K., Avena Bustillos, R.D., Olsen, C.W., Mc Hugh, T.H., Bechtel, P.J. 2005. Characterization of fish skin gelatin gels and films containing the antimicrobial enzyme lysozyme. Annual Meeting of the Institute of Food Technologists.
Technical Abstract: Fish skins are rich in collagen and can be used to produce food-grade gelatin. However, fish collagens have fewer proline and hydroxyproline residues, resulting in less hydrogen-bonding and lower gelling temperatures than mammalian-derived counterparts. Films cast from fish skin gelatins are stable at room temperature and can act as a barrier when applied to foods. Lysozyme is a food-safe, antimicrobial enzyme that can also produce a gel. We believe that fish skin gelatin films can be enhanced with lysozyme and applied as food coatings to increase microbial safety. The objective of this study was to characterize the effect on strength and barrier properties of lysozyme-enhanced fish skin gelatin gels and films, and evaluate their activity against potential spoilage bacteria. Alaskan pollock skins were washed and dried before gelatin extraction. A commercial cold water fish skin gelatin was also used. Solutions containing 6.67% gelatin were formulated to contain varying levels of hen egg white lysozyme. Gels were evaluated for strength, clarity, and viscoelastic properties. Films were evaluated for water activity, water vapor permeability and antimicrobial barrier capabilities. Fish skin gels containing 0.1% to 1.0% lysozyme had pH (4.8) and gelling-temperatures (4.4°C) similar to the lysozyme-free fish skin gelatin controls. However, gel strength decreased (up to 20%). Turbidities of gels, with or without lysozyme, were comparable at all concentrations. Films cast with gelatin that contained lysozyme demonstrated similar water vapor permeabilities (< 5% difference from control), and water activities (0.37). Lysozyme was still detectable in most fish gelatin films. More antimicrobial activity was retained in films cast with higher lysozyme concentrations, and in films where lysozyme was added after the gelatin had been initially heated. These results suggest that fish skin gelatin gels and films, when formulated with lysozyme, may provide a unique, functional barrier to increase the shelf-life of food products.