Inhibition of Four Strains of Spoilage Bacteria by Plasma Technique Synergised With Essential Oil of Oregano

ABSTRACT Serratia liquefaciens (P20), Carnobacterium maltaromaticum (P9), Leuconostoc mesenteroides (P6), and Staphylococcus xylosus (P2) are common spoilage microorganisms in meat products, negatively impacting their nutritional quality and flavor while accelerating spoilage. To extend their shelf life, plasma as a novel non‐thermal sterilization technology developed in recent years, can be applied to suppress microbial growth. Oregano essential oil (OEO) also exhibits strong antimicrobial activity, but the synergistic effect of plasma and OEO remains poorly studied. In this study, we evaluated the bactericidal effects of plasma and OEO, both individually and in combination, against these four bacterial strains. Nucleic acid and protein absorbance increased by 0.294/0.234 (P20) and 0.249/0.184 (P9). Additionally, conductivity rose by 3.9 and 2.96 ms/cm, respectively. The results indicated that the integrity of the cell membrane was compromised, thus increasing its permeability. The inhibitory effect of OEO was determined by the minimum inhibitory concentration (MIC) and the diameter of the circle of inhibition. The MICs of P20, P9, P6 and P2 were 15.6, 15.6, 31.2, and 62.5 mg/mL, respectively. The concentration of OEO was directly proportional to the diameter of the circle of inhibition, and plasma binding with OEO showed a better inhibitory effect. The combination of plasma and OEO showed better bacterial inhibition, with P20, P9 and P6 being able to completely inhibit bacterial growth after 120 s of treatment, whereas P2 was completely sterilized at 35 kV for 120 s.