Effect of Boiss. Essential Oil, NaCl, Acid, Time, and Temperature on the Growth of Strains in Broth and Minced Rainbow Trout

The small outbreaks of listeriosis as one of the leading causes of food poisoning-associated deaths occur more than previously reported. In current study, the growth ability of strains isolated from different sources of food and human origin was measured under salt stress (0.5%, 2.5%, 5%, 7.5%, and 10%) and acid environments (pH = 6.64 and 5.77) for 96 hr by using a Bioscreen C microbiology reader at 37°C. In further steps of this study, after analysis of constituents of Boiss. essential oil (ZMEO), the sensory evaluation of the treated fish meat with ZMEO was performed. Then, the fish isolate of was exposed to sensory acceptable and subminimum inhibitory concentrations (subMICs) of ZMEO in fish broth and minced fish meat during incubation at abuse (12°C), room (22°C), and optimum (37°C) temperatures for 48 hr. The MIC of NaCl against four strains of was 10% at 37°C. The maximum optical densities (ODs) and under curve areas (AUC) of growth patterns in higher pH value and lower contents of NaCl followed the order of 21C > 6F > 66C > 22C of strains, while the lag time was prolonged in the reverse order. The maximum OD, growth, and lag times of samples treated with higher contents of NaCl and lower pH value were affected in a different order. The organoleptic evaluation showed that the fish meat treated with less than 0.5% of ZMEO was sensory acceptable. The population of remained relatively constant at the inoculation level of 10 cfu/ml (or g) at 12°C in broth and minced fish mediums. The inhibitory antilisterial activity of essential oil as an extensive-used plant for food and pharmacological applications is negligible due to possible adverse sensory and toxic effects at relevant high doses.