Aim: Biogenic amines are important indicators of spoilage in vacuum-packed cold-smoked salmon. It is the aim of this study to identify bacteria responsible for biogenic amine production in cold-smoked salmon. Methods and Results: The present study identi®ed spoilage micro¯ora from cold-smoked salmon and determined biogenic amine production of single and co-cultures growing in cold-smoked salmon. Photobacterium phosphoreum was the only species that produced histamine when inoculated on sterile cold-smoked salmon. Production of putrescine was enhanced 10±15 times when cultures of Serratia liquefaciens or Hafnia alvei were grown with Carnobacterium divergens or Lactobacillus sakei subsp. carnosus. This phenomenon was explained by interspecies microbial metabolism of arginine, i.e., metabiosis. Conclusions: The amounts of biogenic amines produced by single and co-cultures corresponded to those observed during spoilage of naturally-contaminated cold-smoked salmon. Photobacterium phosphoreum and Lact. curvatus were identi®ed as the speci®c spoilage organisms in cold-smoked salmon. Signi®cance and Impact of the Study: Determination of the speci®c spoilage organism is needed before a model can be developed for shelf-life predictions of cold-smoked salmon.

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Production of biogenic amines during chill storage of 12 lots of cold-smoked salmon was studied. These data allowed for a multiple compound quality index to be developed by multivariate regression (partial least square regression). The quality index was based on concentrations of cadaverine, histamine, putrescine, and tyramine and pH and showed good correlation with sensory assessments. Biogenic amines were indicators of spoilage rather than casual agents of spoilage off-flavors. Four different biogenic amine profiles were found at the time of spoilage in cold-smoked salmon. These were the results of differences in the spoilage microflora. Histamine was detected above regulatory limits but below toxic levels. Measurements of salt and dry matter for calculation of water phase salt could be substituted by rapid water activity measurements.

Changes were studied in the concentration of 38 volatile compounds during chilled storage at 5 degrees C of six lots of commercially produced vacuum-packed cold-smoked salmon and sterile cold-smoked salmon. The majority of volatile compounds produced during spoilage of cold-smoked salmon were alcohols, which were produced by microbial activity. Partial least-squares regression of volatile compounds and sensory results allowed for a multiple compound quality index to be developed. This index was based on volatile bacterial metabolites, 1-propanol and 2-butanone, and 2-furancarboxaldehyde produced by autolytic activity. Only a few of the volatile compounds produced during spoilage of cold-smoked salmon had an aroma value high enough to indicate contribution to the spoilage off-flavor of cold-smoked salmon. These were trimethylamine, 3-methylbutanal, 2-methyl-1-butanol, 3-methyl-1-butanol, 1-penten-3-ol, and 1-propanol. The potency and importance of these compounds was confirmed by gas chromatography-olfactometry. The present study provides valuable information on the bacterial reactions responsible for spoilage off-flavors of cold-smoked salmon, which can be used to develop biosensors for on-pack shelf-life determinations.

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