ARS | Publication request: BARRIER PROPERTIES, GEL STRENGTH, AND MICROBIAL SAFETY OF FISH SKIN GELATIN GELS AND FILMS

Submitted to: Aquaculture America Conference
Publication Type: Abstract
Publication Acceptance Date: August 3, 2005
Publication Date: February 15, 2006
Citation: Bower, C.K. 2006. Barrier properties, gel strength, and microbial safety of fish skin gelatin gels and films. Aquaculture America Conference.

Technical Abstract: Collagen from fish skins can be used to produce food-grade gelatin, however cold-water fish-skin gelatins solidify at lower temperatures (8 to 10 °C) than their mammalian counterparts (30 to 35 °C). The differences in gelation and melting temperatures are due to the amino acid composition and molecular weight distribution of the gelatins. This makes it difficult for cold-water fish-derived gelatin gels to substitute for gels prepared from the skins of cattle and pigs. Fortunately, fish-skin gelatins have unique functional properties that set them apart from other gelatins. For example, films cast from fish-skin gelatins are stable at room temperature and have moisture barrier properties superior to mammalian-derived gelatins. Current fish processing operations can now mechanically separate skins from other fish components, making it economically feasible to collect discarded skins for production of high value fish-skin gelatin of acceptable quality for food and pharmaceutical use. The purpose of this study was to evaluate the properties of cold-water fish-skin gelatin gels and films in terms of gel strength, barrier properties, and the potential for retaining antimicrobial activity when antibacterial agents such as lysozyme are incorporated. Although the water activities of fish-skin gelatin films were identical (0.37 +/- .01), regardless of whether an antimicrobial agent had been added, the water vapor permeabilities were higher when 1.0% lysozyme was present, (an increase from 0.94 to 1.20 g.mm/m2.h.kPa at 25°C, 80 %RH), thereby decreasing the value of the film as a bather to moisture. The addition of lysozyme did not affect gelling temperatures, which occurred at the same temperature as the control (4.4°C). However, the lysozyme did reduce the solubility and gave a lower overall gelatin gel strength (by up to 20%). Antimicrobial activity was still detectable in most lysozyme-enhanced fish-skin gelatin films. Some bacteria were present in the dry gelatin powders being tested, however no colonies survived at high (gelatin-processing) temperatures and none demonstrated gelatinase activity. Cold-water fish-skin gelatin gels and films may prove valuable, (either alone or produced with antimicrobial agents) as unique, functional bathers for increasing the shelf-life of foods.