Effect of temperature and salt on thermal inactivation of Listeria monocytogenes in salmon roe

Abstract

Listeria monocytogenes is a potentially fatal foodborne pathogen that can be found in ready-to-eat seafood products, such as fresh salmon roe. Once contaminated, salmon roe must be decontaminated prior to human consumption. This study was conducted to determine the thermal inactivation kinetics of L. monocytogenes in raw salmon roe as affected by bacterial strain, temperature, and salt concentration. Three different strains of L. monocytogenes, including serotype 4b (F2365), 1/2b (F4260), and 1/2a (V7), were individually inoculated to salmon roe supplemented with salt (0-4.5%), and heated under different temperatures (57.5-65.0°C) to evaluate the survival of the bacterium during heating and determine the D-values. Results showed that the thermal resistance (log D) of L. monocytogenes was significantly affected by bacterial strain, temperature, and salt and by their interactive effects, with strain F2365 being the most heat-resistant among all three strains tested. Salt added to salmon roe significantly increased the thermal resistance of the bacteria. For L. monocytogenes F2365, the z value of the bacterium in salmon roe was 5.99°C, and its heat resistance increased with the level of salt in a linear manner. The results of kinetic analysis and the models obtained in this study may be used by the seafood industry to develop proper thermal processes to eliminate L. monocytogenes in raw salmon roe and to ensure microbial safety and prevent foodborne illness.

Shelf-life of loricariid catfish (Pterygoplichthys disjunctivus [Weber, 1991]) roe stored in ice

“…Likewise, Hsu et al (1983) recorded only small variations in an intermediate moisture mullet (Mugil cephalus) roe product, with an initial 0.84 a w , stored at 5 °C for 30 days. On the other hand, the low a w obtained in the present study contrasts with the fresh salmon roe values reported by Li et al (2017), which were higher (0.96-0.98) than the ones obtained in the present study. This low value in the loricariid catfish roe is capable of holding the growing of certain microorganisms, helping to prolong its shelf life.…”

Heat Resistance of Listeria monocytogenes in Dairy Matrices Involved in Mozzarella di Bufala Campana PDO Cheese

“…Considering the values obtained in hardening water and brine, the relatively low NaCl concentration (4 g/100 g) of the latter fluid did not markedly affect Lm15 heat resistance, probably because the protective effect of salt was counterbalanced by the low pH value of the brine. The direct relation between salt concentration and L. monocytogenes thermotolerance was observed by several authors (Jørgensen et al, 1995;Juneja et al, 2013;Li et al, 2017).…”

Thermal resistance of Listeria monocytogenes and background microbiota in unsalted and 10% salted liquid egg yolk

“…For L. monocytogenes , three strains of different serotypes, including 4b (F2365), 1/2b (F4260), and 1/2a (V7) were used in this study. These strains were the same as those used in Li, Huang, and Hwang (), and were induced to resist to 100 mg/L of rifampicin (Sigma, R 3501‐5G, Sigma‐Aldrich Co., MO). The purpose of using rifampicin‐resistant strains of L. monocytogenes was to differentiate it from numerous background bacteria in the LEY samples.…”

“…To each filter bag, a small volume (0.1 mL) of L. monocytogenes cocktail was added, allowing the initial inoculum level to reach 10 8–8.5 CFU/g in LEY. The sample bags were flattened, vacuumed to remove the air, and then sealed (Li et al, ). This procedure was used to ensure uniform heating in the samples.…”