U. Lyhs et al., The spoilage flora of vacuum-packaged, sodium nitrite or potassium nitratetreated, cold-smoked rainbow trout stored at 4 degrees C or 8 degrees C, INT J F MIC, 45(2), 1998, pp. 135-142
The spoilage flora of vacuum-packaged, salted, cold-smoked rainbow trout fi
llets, with or without the addition of nitrate or nitrite, stored at 4 degr
ees C and 8 degrees C, was studied. Of 620 isolates, lactic acid bacteria w
ere the major fraction (76%), predominating in all samples of spoiled produ
ct. However, the phenotypical tests used were insufficient to identify the
lactic acid bacteria to the species level. Gram-positive, catalase-positive
cocci, Gram-negative, oxidase-negative rods and Gram-negative, oxidase-pos
itive rods were found in 6%, 16% and 2% of the samples, respectively. Of 39
Gram-positive, catalase-positive cocci, 29 were identified as staphylococc
i and 10 as micrococci. Eighty-five isolates were found to belong to the fa
mily Enterobacteriaceae, with 45 of those being Serratia plymuthica. Eleven
isolates from the nitrate treated samples stored at 8 degrees C were ident
ified as Pseudomonas aeruginosa. The occurrence of P. aeruginosa and staphy
lococci in the nitrate-containing samples, stored at 8 degrees C, may cause
problems with respect to the safety of the product. The types of lactic ac
id and other bacteria in the spoilage flora were generally reduced by the a
ddition of nitrate or nitrite to fillets. (C) 1998 Elsevier Science B.V. Al
l rights reserved.