Abstract:The specific spoilage organisms (SSO) in cultured tilapia at the end of shelf life during storage at 0, 5 and 10 ℃ were qualitatively and quantitatively investigated, and the growth model of SSO was established. The results indicated that the percentage of Pseudomonas spp. in total bacteria in the tilapia were 807%，681% and 575% at the end of shelf life of tilapia stored at 0, 5 and 10 ℃, respectively. Colonies of Pseudomonas spp. on nutrition agar and trypticase soy broth agar were circular apophysis with smooth edge, transparent and colourless; The cells were gram negative rod (0.5-0.7 μm×1.6-3.2 μm) and motile by means of polar flagellum; Positive for oxidation，but the strains could not assimilated trehalose, mannitol and raffinose, etc. A variety of acids were detected in these organisms, including branched and straight chained acids, cyclopropane, and hydroxy acids. Unsaturated fatty acids comprised a large part of all fatty acids (50.18%), and the major ones were 16∶1ω7c, iso 15∶0, 16∶0 and 17∶1ω8c, which were 26.16%, 14.83%, 7.96% and 3.94% of total fatty acids, respectively. The type of ribosome of these bacteria was 56-S-7, as tested by Riboprinter. The growth dynamic for Pseudomonas spp. was fitted by modified Gompertz equation. The results showed that lag time reached（59.63±61.88）, (7.25±24.06) and （3.95±9.83）h during storage at 0, 5 and 10 ℃, respectively. The maximum specific growth rates for Pseudomonas spp. were （0.02±000）h-1, （0.04±0.00）h-1 and （0.08±0.01）h-1 at 0, 5 and 10 ℃, respectively.
