Study On Effect Of Synergistic Treatment Of Thymol And Cinnamaldehyde On Preservation Of Salt-baked Chicken And Its Antibacterial Mechanism

Salt-baked chicken,one of the Hakka dishes in Guangdong province,is popular among consumers due to its unique flavor.However,the shelf-life of salt-baked chicken is extremely short,which limits its development in modern industry.Hence,extending the shelf-life of salt-baked chicken and ensuring the health and safety of consumers while maintaining its original flavor and characteristics is still a research hotspot recently.In this study,in vitro antibacterial effects of thymol(THY)and cinnamaldehyde(CIN)against L.monocytogenes and S.typhimurium were investigated.Besides,the preservation effects of THY and CIN in combination on salt-baked chicken were also studied.The specific findings of the study are as follows:Antibacterial effects of THY and CIN: The MICs and MBCs of THY and CIN against L.monocytogenes were 0.25 mg/m L and 0.5 mg/m L,respectively.Furthermore,the FICI of THY and CIN against L.monocytogenes was 1.0,indicating that their combination exhibited an additive effect.The MICs and MBCs of THY and CIN against S.typhimurium were 0.25mg/m L and 0.5 mg/m L,respectively.Furthermore,the FICI of THY and CIN against S.typhimurium was 0.75,indicating that their combination showed a synergistic antibacterial effect.The above results were confirmed by the results of time-kill curves,SEM analysis,PI uptake tests and bacterial motility assay,which revealed that the integrity of bacterial cell membrane and ultrastructure were disrupted by THY combined with CIN,thereby causing the leakage of cell contents and bacterial inactivation.The preservation effects of THY and CIN in combination on salt-baked chicken:Compared with the control,the declining trend of sensory score and spoilage degree of salt-baked chicken was decreased by THY and CIN in combination,and the increasing trend of pH,microbial growth and lipid oxidation were also inhibited by the combined treatments.The total viable count of the control group exceeded the limit on the 8th day,while the corresponding day for treatment group was 16 th day.In the control group and combined treatment group,the pH value reached the maximum on the 4th and 6th day,which were6.24±0.01 and 6.18±0.02,respectively.On the 16 th day,the TVB-N values reached maximum values of 36.73±0.59 mg/100 g and 18.77±0.83 mg/100 g in the control and antimicrobial treated groups,respectively,and the TBARS values also reached maximumwhich of the control group and the thy and CIN combined treatment group were 6.24±0.08 mg/kg and4.42±0.18 mg/kg respectively.These results indicated that THY and CIN,as natural antimicrobial agents,can be applied to preserve freshness of salt-baked chicken to achieve better preservation effect.The combined antibacterial mechanism of THY and CIN against L.monocytogenes: The combination of THY and CIN could reduce the integrity of bacterial cell membrane and cause membrane protein loss or function damage,thereby interfering with the normal physiological function of L.monocytogenes.In addition,THY and CIN entering the cell would interfere with pyrimidine metabolism and the activities of some enzymes related to DNA splicing and repair,thus affecting the synthesis of DNA and other nucleic acid substances.Meanwhile,the damaged genetic material could not be effectively repaired,resulting in serious disorder of bacterial intracellular metabolism,and eventually leading to cell lysis and death.In conclusion,the combined treatment of THY and CIN can be used as a natural compound antibacterial agent for the preservation of salt-baked chicken;the antibacterial mechanism of THY and CIN on L.monocytogenes was revealed,which is helpful for the application of THY and CIN in food industry.