Utilization of chitosan for preservation of raw shrimp (Pandalus borealis)

Whole and headless shrimp (Pandalus borealis) were dipped in various concentrations of chitosan solution and stored for 20 days at 4-7 degrees C. The effects of chitosan on microbial proliferation, total volatile bases, nucleotide breakdown, and blackspot formation were monitored over this period. Chitosan showed strong antimicrobial properties inhibiting several microorganisms at concentrations ranging between 0.0075 - 0.01%. The Pseudomonads, however, were very resistant to chitosan requiring much higher concentrations (0.1%) for inactivation. Chitosan reduced the levels of total volatile bases but had no effect on nucleotide breakdown. On the incidence of melanosis, there were no significant differences (p > 0.05) between samples treated with chitosan and the non-treated samples although blackspot formation was more extensive in whole than headless shrimp. Furthermore, treatment of shrimp with 2% chitosan showed consistently lower incidence of melanosis during storage. The results suggest that chitosan may prove useful as a tool for controlling microbial spoilage of shrimp, but may be limited by its ineffectiveness at controlling melanosis in the postmortem animal.