Journal article
Evaluation of the role of Carnobacterium piscicola in spoilage of vacuum- and modified-atmosphere-packed cold-smoked salmon stored at 5 degrees C
The microflora on spoiled cold-smoked salmon often consists of a mixture of lactic acid bacteria (LAB) and Gram-negative bacteria. To elucidate the role of the different groups, a storage trial was carried out in which nisin and CO2 were used for the selective inhibition of the two bacterial groups.
The shelf-life of vacuum-packed cold-smoked salmon, recorded by sensory evaluation, was four weeks at 5 degrees C and the microflora was composed of LAB (10(6)-10(7) cfu/g) with an associate Gram-negative flora in varying levels (10(5)-10(7) cfu/g). The addition of nisin and/or a CO2-atmosphere increased the shelf-life to five or six weeks and limited the level of LAB to about 10(4)-10(6), 10(3)-10(6) and 10(2)-10(4) cfu/g, respectively.
CO2-atmosphere+/-nisin inhibited the growth of Gram-negative bacteria, whereas nisin had no effect on these in vacuum packages. The Gram-negative flora on vacuum-packed salmon was dominated by a Vibrio sp., resembling V. marinus, Enterobacteriaceae (Enterobacter agglomerans, Serratia liquefaciens and Rahnella aquatilis) and occasionally Aeromonas hydrophila.
Irrespective of the addition of nisin and/or CO2- atmosphere, the LAB microflora was dominated by Carnobacterium piscicola, which was found to account for 87% of the 255 LAB isolates characterized. Whole-cell-protein patterns analysed by SDS-PAGE confirmed the Carnobacterium species identification. The spoilage potential of C. piscicola isolates was further studied by inoculation of approx. 10(6) cfu/g in cold-smoked salmon stored at 5 degrees C.
The salmon did not spoil within 4 weeks of storage in vacuum-or CO2-atmosphere, and it is concluded that despite high levels (> 10(7) cfu/g) of C. piscicola, sensory rejection was caused by autolytic changes. This was supported by the development of soft texture and sour, rancid and bitter off-flavours at the point of spoilage, irrespective of the length of shelf-life and low or high total counts of LAB and Gram-negative bacteria. (C) 1998 Elsevier Science B.V
Language: | English |
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Year: | 1998 |
Pages: | 155-166 |
ISSN: | 18793460 and 01681605 |
Types: | Journal article |
DOI: | 10.1016/s0168-1605(97)00133-5 |
ORCIDs: | Dalgaard, Paw and Gram, Lone |
Animals Bacterial Proteins Carbon Dioxide Cold Temperature Colony Count, Microbial Electrophoresis, Polyacrylamide Gel Evaluation Studies as Topic Fish Products Food Microbiology Food Packaging Food Preservation Food Preservatives Gram-Negative Bacteria Gram-Positive Bacteria Hydrogen-Ion Concentration Methylamines Nisin Nitrogen Odorants Salmon Sodium Chloride Vacuum trimethylamine trimethyloxamine