Effects of salt and storage temperature on chemical microbiological and sensory changes in cold-smoked salmon

Chemical, microbiological and sensory changes during storage of vacuum-packed cold-smoked salmon were studied using a factorial experimental design with two storage temperatures (5 and 10 °C) and two salt levels (2.2 and 4.6%). The spoilage characteristics were typical of microbiological activity in all treatments, but there was no relation between sensory changes and any of the microbiological numbers (total viable counts, total psychrotrophes, lactic acid bacteria or Enterobacteriaceae). Total viable counts typically reached 10⁸ cfu/g weeks before sensory rejection. Acetic acid, hypoxanthine, trimethylamine and ethanol concentrations increased with storage time in all treatments. The increase in ethanol depended on salt concentration but not storage temperature. Absolute values of trimethylamine ranged from 2-8 mg TMA-N/100 g initially, to 10 mg TMA-N/100 g at sensory rejection. Acetic acid levels increased with temperature and decreased with salt concentration, but varied between 12-23 μmol g at rejection. Initial concentrations of hypoxanthine increased from 2-3 μmol g to maximum 8-9 μmol g, with values of 5-7 μmol g indicating the limit of sensory acceptability. Hypoxanthine was considered to be the best objective indicator for sensory quality of cold-smoked salmon.