Thermal Sterilization of Listeria Monocytogenes and Kinetics of Quality Changes in Cold Smoked Salmon
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Abstract:
In order to provide a theoretical foundation for the thermal sterilization of cold smoked salmon, the influence of heat treatments on the inactivation of Listeria monocytogenes and the changes in the quality of cold smoked salmon were investigated. A sample of cold smoked salmon inoculated with a strain of L. monocytogenes (ATCC19113) was sealed in a capillary tube, and subjected to heat treatment at 58 ℃, 60 ℃, 62 ℃, 64 ℃, and 66 ℃ for 18 min, 8.8 min, 4 min, 2 min, and 1 min, respectively. The changes in viable bacterial cell count at the different temperatures was monitored. Small samples (D 30 mm × H 6 mm) were sealed in an aluminium heating unit (D 35 mm × H 6 mm) and heated in a water bath at 50 ℃, 57 ℃, 64 ℃, and 70 ℃ for 120 min, 90 min, 60 min, and 40 min, respectively. The corresponding changes in quality were studied. The results showed that the inactivation curve exhibited a logarithmic linear relationship (R2 ≥ 0.94). The quality indexes of cold smoked salmon, including cooking loss, the a* value, b* value, and the shear force followed first-order reaction kinetics, while the L* value followed zero-order reaction kinetics. As the a* value of cold smoked salmon was closely linked to thermal inactivation of L. monocytogenes, the overlapping region between thermal-death-time curves of L. monocytogenes (ATCC19113) and the a* quality deterioration curve was the operational range to carry out the combination of temperature and heat treatment time, which could meet the requirements for sterilization without deteriorating quality of cold smoked salmon.
