Effect of yogurt-based marinade combined with essential oils on the behavior of Listeria monocytogenes, Escherichia coli O157:H7 and Salmonella spp. in camel meat chunks during storage

Abstract

The present study evaluated the effect of yogurt-based marinade combined with active essential oil components (EOs) namely: thymol (TH), carvacrol (CA), and cinnamaldehyde (CI) on Listeria monocytogenes, Escherichia coli O157:H7 and Salmonella spp. in camel meat (CM) chunks during storage at 4 and 10 °C. Fresh cocktail mixtures of L.monocytogenes, E. coli O157:H7 and Salmonella spp. strains were inoculated on CM samples. Subsequently, a yogurt-based marinade, with or without 1% or 2% of the added EOs, was mixed with the CM chunks. After treatment, marinated camel samples were stored at 4 and 10 °C for 0, 1, 4 and 7 days. Adding yogurt-based marinade to the CM samples did not cause any significant changes in L.monocytogenes, E. coli O157:H7 and Salmonella spp. numbers at 4 °C, but at 10 °C resulted in a significant decrease in numbers on day 4 and 7 of storage by 1.4-1.5; 2.7-2.1 and 2.5-2.8 log CFU/g, respectively, compared to untreated CM samples. The incorporation of EOs into the CM with marination (CMM) further enhanced the microbial reduction of E. coli O157:H7 and Salmonella. At 10 °C, the synergistic effect of EOs with marinade was greater than at 4 °C. Increasing the concentration of the EOs used in this study from 1% to 2%, enhanced E. coli O157:H7 and Salmonella spp. reduction during storage at 4 and 10 °C while L.monocytogenes numbers were not affected. Increasing active EO component concentrations to 2% caused further significant reductions in Salmonella spp. in the CMM samples during storage by 1.0-2.7 log CFU/g (P ˂ 0.05) at 4 and 10 °C. At 10 °C, increasing the concentration of CI and TH to 2% caused a further reduction (P ˂ 0.05) of E. coli O157:H7 numbers by days 4 and 7 in the range of 3.6-4.4 log CFU/g. Among all tested EOs, 2% TH and 2% CI had the greatest effect against E. coli O157:H7 and Salmonella spp. in CMM during storage at 4 and 10 °C. In comparison to CMM, the highest scores of all examined sensory attributes were found in CMM samples with 1% and 2% CI added. Results indicate that the EO component CI can be used as an effective tool to decrease populations of E. coli O157:H7 and Salmonella spp. in CM with minor sensory changes.

Keywords: Camel meat; Carvacrol; Cinnamaldehyde; Foodborne pathogens; Marination; Sensory evaluation; Thymol.