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 thePseudomonas fragigroup (8–30·8%) andShewanella putrefaciens(1·8–11%). A significant presence was also noted for fluorescentPseudomonas(15·6–18·4%) andPsychrobacter immobilis(16·4–23·4%). The isolation frequency of the other groups decreased during storage. The most important proteolytic species werePseudomonas fluorescensandShewanella putrefaciensand the most lipolytic bacteria werePsychrobacter immobilisand again,P. fluorescensandS. 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 putrefacienswas the strongest spoiler, followed byPseudomonas fluorescens. A weaker activity was observed for strains ofPseudomonas fragi, enterobacteriaceae and non-saccharolytic pseudomonads. The contribution of weak spoiler bacteria can be undermined by the activity of the strongest spoilers, but in some cases the considerable incidence of the former group suggests their effective role.Morganella morganiiwas the only histamine-producing species among 57 screened strains representative of different taxa.