The Effect of Cold Chain Disruption on the Microbiological Profile of Chilled Fish

Abstract

Cold chain interruption during transport of samples to the laboratory may become a confounder in food hygiene practice. This study evaluates the influence of inadequate transport conditions on the microbiological quality of fish fillets from common carp (Cyprinus carpio), Atlantic salmon (Salmo salar), and Atlantic cod (Gadus morhua) packaged in plain, vacuum, or modified atmosphere packaging (MAP). The experiments simulated the temperature increase during sample transport to 3, 5, 8, 11, 14, 17, 20, and 25 °C with exposure times of 1, 2, 3, and 4 h. Aerobic plate count (APC), psychrotrophic microorganisms count (PMC), β-D-glucuronidase-positive Escherichia coli, and Salmonella spp. were evaluated immediately after the exposure to the elevated temperature (0 h), 3 h, and 24 h after the return to the normal temperature. Variability was observed even in the initial microbial contamination of fish fillets. Storage at higher temperatures led to an increase in microbial contamination of fish fillets Different types of packaging also played a role. In non-fatty fish (cod), CO2-containing MAP led to a decrease in pH and, therefore, to lower microbial growth. In fatty fish (salmon), the presence of CO2 did not lead to the reduction in pH and the degree of microbial contamination was, therefore, not affected by this intrinsic factor. If cold chain interruption occurs during the transport of samples to the laboratory, it is necessary to perform the analysis immediately as even storage in cold conditions until the next day can lead to increased levels of microbial contamination of such samples.