The microflora of fresh and spoiled sardines (Sardina pilchardus) caught in Adriatic (Mediterranean) Sea and stored in ice

A total of 1500 strains were isolated from the skin and gills of fresh, ice-stored (4 days) and spoiled (8 days) Adriatic sardines, and were identified at different taxonomic levels. Fresh sardine microflora found included mostly non-fermenting Gram-negative bacteria, (Pseudomonas, Flavobacterium, Psychrobacter, Acineobacter, Shewanella), and a minor proportion of Enterobacteriaceae and Gram-positive bacteria. The highest increase in microflora frequency, after 8 days in ice, was observed for the Pseudomonas fragi group (8-30.8%) and Shewanella putrefaciens (1.8-11%). A significant presence was also nosed for fluorescent Pseudomonas (15.6-18.4%) and Psychrobacter immobilis (16.4-23.4%). The isolation frequency of the other groups decreased during storage. The most important proteolytic species were Pseudomonas fluorescens and Shewanella putrefaciens and the most lipolytic bacteria were Psychrobacter immobilis and again, P. fluorescens and S. putrefaciens. A total of 288 isolates, representative of the main groups, were tested for potential spoiling activity (H2S and off-odour production, TMAO reduction). Shewanella putrefaciens was the strongest spoiler, followed by Pseudomonas fluorescens. A weaker activity was observed for strains of Pseudomonas fragi, enterobacteriaceae and non-saccharolytic pseudomonads. The contribution of weak spoiler bacteria can be undermined by the activity of the strongest spoilers, bur in some cases the considerable incidence of the former group suggests their effective role. Morganella morganii was the only histamine-producing species among 57 screened strains representative of different taxa. (C) 1999 Academic Press.