Abstract:

Objective: Changes in the sensory and microbial quality, pH and dominant microflora of pomfret (Pampus
argenteus) from different growing seasons (winter and spring)were investigated during chilled storage. Methods: Based
on the results of sensory evaluation, pH and total viable count (TVC), the diversity of dominant spoilage bacteria in
pomfret were monitored by the combination of PCR amplification with physiological and biochemical identification. After
separation and purification of dominant spoilage bacteria in pomfret, the single colony types of bacteria were classified
according to their morphological features, physio-biochemical identification, Gram staining, DNA extraction, PCR
amplification and sequencing. Results: Totally 12 strains of bacteria were obtained in winter samples (WS) and 9 strains
of bacteria in spring samples (SS). The dominant spoilage bacteria in WS included 21.51% Psychrobacter spp., 16.13%
Pseudomonas fragi, 52.68% Pseudomonas fluorescens and 9.68% Brochothrix thermosphacta, while those in dominant
spoilage bacteria in spring samples (SS) included 8.62% Pseudomonas fragi, 64.66% Pseudomonas fluorescens and 26.72%
Shewanella putrefaciens. Conclusion: The species of dominant spoilage bacteria in pomfrets from both seasons during
chilled storage were mainly composed of Gram-negative bacteria, the species and proportion of bacteria were different
between the two seasons. Microbial species were more abundant in winter than those in spring. With the high proportion of
Pseudomonas fluorescens, the growth of Shewanella putrefaciens was inhibited obviously during chilled storage.

Key words: Pampus argenteus, different growing seasons, chilled storage, dominant spoilage bacteria, microbial diversity