A chitosan-gelatin blend as a coating for fish patties

A coating made in cold from a blend of a chitosan and a gelatin solution was applied to patties made of chilled cod, and its preservative effect was assessed by colour measurements, rheological measurements (hardness, elasticity, cohesiveness, chewiness, gumminess, and adhesiveness), biochemical determinations (total volatile bases and thiobarbituric acid as measures of rancidity) and microbiological assays (total bacterial counts, luminiscent bacteria, enterobacteria, pseudomonas, lactic acid bacteria, and Staphylococcus aureus). The effect of dry powdered chitosan mixed into the patties was tested as well. The use of chitosan either as a coating or as a powdered ingredient did not affect lightness at the end of the storage period considered but did result in an increase in the value of yellowness. The coating increased patty elasticity, whereas adding powdered chitosan to the patty mixture increased the other rheological parameter values. The findings on the effect of the chitosan on rancidity were not conclusive due to the low values recorded in the cod. However, the coating did prevent spoilage of the cod patties as reflected by a decrease in total volatile basic nitrogen and in the microorganism counts, in particular counts of gram-negative bacteria. In contrast, none of these effects on spoilage were observed when the chitosan was added to the patty mixture in powdered form. Coatings prepared in cold from a blend of gelatin and chitosan offer a promising alternative for preserving fish patties. (C) 2004 Elsevier Ltd. All rights reserved.