Microbial chitosan as a biopreservative for fish sausages.

Processed fish products are worthy sources to supply man with his main nutritional needs, but they are extremely susceptible to quality loss during storage. Microbial (fungal) chitosan is a bioactive polymer that has numerous applications in health promoting fields. Fungal chitosan was extracted from the grown mycelia of Aspergillus brasiliensis (niger) to investigate its potential role as antimicrobial, preservative and quality improvement agent, in processed fish sausages from Nile tilapia (Oreochromis niloticus). The produced chitosan had a molecular weight of 29kDa, deacetylation degree of 91% and solubility of 99% in acetic acid solution. Fish sausages supplementation with 1.5% chitosan resulted in sharp reductions of microbial load (Total aerobic microorganisms, coliforms, yeast & molds, E. coli, Enterobacteriaceae and Staphylococcus aureus) during cold storage, at 4°C for 28days. Sensory attributes were notably enhanced in stored chitosan-supplemented sausages, especially the odor and taste characteristics. Captured micrographs, of exposed S. aureus to chitosan, exhibited vigorous morphological alterations after 4h, and complete cell lysis after 8h of exposure period. A. brasiliensis chitosan, however, could be strongly recommended, as a supplement for Nile tilapia fish sausages, to maintain microbiological quality and enhance sensory attributes of the product during storage.