Effect of water activity and storage temparature on the quality and microflora of smoked salmon

Two types of smoked salmon in the Aw range above 0.93 and less than 0.96 (L-Aw type) and above 0.96 (H-Aw type) were prepared, sliced, vacuum-packed and then stored for 40, 30, and 5 days at 5, 10, and 20°C, respectively. Changes in sensory evaluation, and microbiological and chemical characteristics were investigated throughout the storage period. The overall sensory score and textural evaluation of the H-Aw type decreased faster than the L-Aw type at each storage temperature. Viable cell counts and VB-N values of the H-Aw type were larger than the L-Aw type at each temperature during the storage period. As for microflora in the H-Aw type, Enterobacteriaceae was significant in the middle period at 10°C, and was very common at 20°C after 2 days of storage. Lactobacillus finally dominated under the temperature conditions examined. In the L-Aw type, Streptococcus and Lactobacillus were predominant on the last day of storage at 20°C, and 10 and 5°C storage, respectively. These findings suggest that the storage temperature and Aw of smoked salmon are closely correlated to shelf-life, because a combination of storage temperature and Aw affected the viable cell counts and formation of microflora during the storage period and induced the changes of sensory evaluation and VB-N values.