Effect of multifactorial free and liposome-coated of bay laurel (Laurus nobilis) and rosemary (Salvia rosmarinus) extracts on the behavior of Listeria monocytogenes and Vibrio parahaemolyticus in silver carp (Hypophthalmichthys molitrix) stored at 4 °C

In this study, the effect of bay laurel (Laurus nobilis) (LE) and rosemary (Salvia rosmarinus) (RE) extracts, in two free forms and loaded with liposome, on the behavior of Listeria monocytogenes and Vibrio parahaemolyticus in silver carp (Hypophthalmichthys molitrix) minced, were examined. After extraction, the extracts were evaluated for phenolic, flavonoid, and antibacterial compounds (determination of MIC and MBC). The treatments studied included control treatment, treatments containing 1 and 1.5% of free extracts, and treatments containing 1 and 1.5% of liposome-coated extracts of LE and RE which were examined at times of 0, 4, 8, and 12 days with 3 replications. The findings indicated that the amount of flavonoid and phenolic compounds and the results of antibacterial tests (MIC and MBC tests) in RE extract were more favorable than LE extract. The aqueous extract of rosemary had higher levels of phenolic (344.66 mg gallic acid/g extract) and flavonoid (245.33 mg Catechin/g extract) compounds compared to the bay laurel extract (257.66 mg gallic acid/g extract) and (151.26 mg Catechin/g extract) respectively. The results of the behavior of L. monocytogenes and V. parahaemolyticus in fish showed that with increasing the storage time at 4 °C, these parameters increased, but in the treatment containing the coated forms of LE and RE extracts (concentration 1.5%), changes were significantly slower than other treatments. According to the obtained results, it can be concluded that in general, adding extracts of bay laurel and rosemary in a concentration of 1.5% reduces the proliferation of bacteria that cause food poisoning.