Antibacterial effect of 460 nm light-emitting diode in combination with riboflavin against Listeria monocytogenes on smoked salmon

Abstract

This study investigated the antibacterial effect of a 460 nm light emitting diode (LED) in combination with riboflavin on the inactivation of Listeria monocytogenes on smoked salmon. The influence of irradiance and temperature on this inactivation was examined. Smoked salmon fillets, surface-inoculated with a 4-strain cocktail of L. monocytogenes and topically administered with 25, 50 and 100 μM riboflavin, were illuminated by 460 nm LEDs at three different irradiances (15, 31 and 58 mW/cm2) and two temperatures (4 and 12 °C). Three conceptually different mathematical models - log-linear, modified Weibull and reduced Baranyi were used to fit the inactivation curves. The color of smoked salmon was also monitored during the illumination. A dosage of 2.4 kJ/cm2 LED illumination in combination with riboflavin caused 0.7–1.2 log CFU//cm2 reductions of L. monocytogenes at all irradiances and temperatures. Three-way ANOVA showed that all the three variables significantly influenced the inactivation of L. monocytogenes (P < 0.05). Significant interaction was observed between concentration and irradiance at 12 °C. Mathematical modeling suggested that the Weibull as well as the Baranyi model best fitted the inactivation curve and thus the Weibull model was subsequently used to compute the dose required for the first log reduction (δ). In most cases, the combination of LEDs and riboflavin was more effective than either treatment alone. The results of this study demonstrate the potential of 460 nm LEDs aided by riboflavin to minimize the risk of L. monocytogenes associated with smoked salmon during storage at food establishments.