Abstract: In this paper,the microbial diversity changes of cutlassfish (Trichiurus haumela) coated with chitosan during chilled storage (4±1 ℃) were investigated.The sensory evaluation,pH value and total viable counts (TVC) were measured in day 0,2,4,6,8,10,12.The strains of samples from different days were separated,purified,DNA extraction and PCR amplification.The results showed that 10.0 g/L of chitosan significantly increased the fresh duration of cutlassfish and inhibited the growth of microorganism.The shelf-life of cutlassfish was prolonged for almost 4-5 days.At the end of spoilage period, the main changes of bacteria in controlled (10 d) were Pseudomonas fragi 29.5%, Pseudomonas fluorescens 33.4%, Shewanella putrefaciens 32.0%, Staphylococcus sciuri 5.1%,and the bacteria of samples (12 d) with chitosan were Pseudomonas fragi 38.2%, Pseudomonas fluorescens 30.1%, Shewanella putrefaciens 29.0%, Brochothrix thermosphacta 2.7%. Chitosan can inhibit the growth of Staphylococcus saprophyticus, Staphylococcus sciuri and Psychrobacter spp, the dominant species were Pseudomonas fragi, Pseudomonas fluorescens and Shewanella putrefaciens.

Key words: Trichiurus haumela, chitosan, microorganism flora, chilled storage