Effectiveness of cell-adsorbed bacteriocin produced by Lactobacillus curvatus CWBI-B28 and selected essential oils to control Listeria monocytogenes in pork meat during cold storage

Aims:  To study the effectiveness of a combination of cell-adsorbed bacteriocin (CAB; a suspension of producer cells on which maximum bacteriocin has been immobilized by pH adjustments) of a Lactobacillus curvatus strain with oregano or savory essential oil to control Listeria monocytogenes in pork meat at 4°C.
Methods and Results:  The antimicrobial activity of the CAB and six different essential oils was tested by the well diffusion assay against L. monocytogenes M, Escherichia coli 10536 and Salmonella serotype Typhi CWBI-H1. The anti- Listeria activity of the CAB and oregano or savory essential oils was also investigated in pork meat. The results of the well diffusion assay showed that CAB was only inhibitory to L. monocytogenes while savory and oregano essential oils were the most active against the three indicator bacteria. In pork meat, Listeria counts have declined from c. 10² CFU g⁻¹ to below the detectable limit during the first week of storage in samples treated with CAB or oregano essential oil and in those treated with CAB combined with oregano or savory essential oil. However, the counts of L. monocytogenes have increased after the third week of storage in all samples with the exception of those treated with the combination of CAB and oregano essential oil. The combination of CAB with savory essential oil resulted in a 2-week delay of the growth rebound compared with samples treated with CAB alone.
Conclusions:  Addition of oregano or savory essential oil exhibited a synergistic effect with CAB to control L. monocytogenes in pork meat during storage at 4°C.
Significance and Impact of the Study:  The combination of CAB with oregano or savory essential oil may be effectively used in meat industry to enhance the safety and stability of meat products.