Microbial Inactivation Property of Pulsed Corona Discharge Plasma and Its Effect on Chilled Pork Preservation

The Combination of Corona Discharge Plasma and ε-Polylysine for the Inactivation of Serratia liquefaciens

The purpose of the study was to investigate the mechanism of inactivation of Serratia liquefaciens by different treatments, namely corona discharge plasma (CDP), ε-polylysine (ε-PL), and corona discharge plasma combined with ε-polylysine (CDP plus ε-PL). The results showed that the combined treatment of CDP and ε-PL exhibited significant antibacterial effects. The total number of colonies of S. liquefaciens dropped by 0.49 log CFU/mL following 4 min of CDP treatment, 4MIC ε-PL treatment for 6 h alone decreased the amounts of colonies by 2.11 log CFU/mL, and 6 h of treatment with 4MIC ε-PL after the bacterium was treated with CDP could decrease the number of colonies by 6.77 log CFU/mL. Scanning electron microscopy images showed that the combined treatment of CDP and ε-PL caused the most serious damage to the cell morphology. Electrical conductivity, nucleic acid, and PI staining indicated that the combined treatment dramatically enhanced the permeability of the cell membrane. In addition, the combined treatment led to a significant decrease in SOD and POD enzyme activities in S. liquefaciens, which prevented energy metabolism. Finally, the determination of free and intracellular ε-PL concentrations confirmed that the treatment of CDP could cause the bacteria to bind more ε-PL and exert more significant bacterial inhibition. Therefore, CDP and ε-PL had a synergistic effect in the inhibition of S. liquefaciens.

Prospects for the next generation of artificial enzymes for ensuring the quality of chilled meat: Opportunities and challenges

As living standards rise, the demand for high-quality chilled meat among consumers also grows. Researchers and enterprises have been interested in ensuring the quality of chilled meat in all links of the downstream industry. Nanozyme has shown the potential to address the aforementioned requirements. Reasons and approaches for the application of nanozymes in the freshness assessment or shelf life extension of chilled meat were discussed. The challenges for applying these nanozymes to ensure the quality of chilled meat were also summarized. Finally, this review examined the safety, regulatory status, and consumer attitudes toward nanozymes. This review revealed that the freshness assessment of chilled meat is closely related to mimicking the enzyme activities of nanozymes, whereas the shelf life changes of chilled meat are mostly dependent on the photothermal activities and pseudophotodynamic activities of nanozymes. In contrast, studies regarding the shelf life of chilled meat are more challenging to develop, as excessive heat or reactive oxygen species impair its quality. Notably, meat contains a complex matrix composition that may interact with the nanozyme, reducing its effectiveness. Nanopollution and mass manufacturing are additional obstacles that must be overcome. Therefore, it is vital to choose suitable approaches to ensure meat quality. Furthermore, the safety of nanozymes in meat applications still needs careful consideration owing to their widespread usage.

Surface dielectric barrier discharge plasma-treated pork cut parts: bactericidal efficacy and physiochemical characteristics

Maintaining agro-food product safety remains a significant challenge for satisfying local and global consumers in tropical countries. This issue has been growing due to new pathogen strains, low infectious doses, increased virulence, antibiotic resistance, cross-contamination or recontamination of foods, food-contact surfaces, and biocontamination of water within the food production chain. To respond to this situation, we studied the inactivation efficacy of surface dielectric barrier discharge (SDBD) plasma against pathogens on the surface of various pork cut parts, including the loin, hip, belly, liver, and intestine. The SDBD plasma was operated at 0.30 W/cm² in ambient air, with a gap of 5.0 mm between the plasma generator and the sample surface. Up to 96% germicidal efficiency against surface pathogens were observed, showing after 1 min of SDBD plasma exposure. Visualization of reactive species deposition on the treated surface using KI-starch agar gel reagent indicated a non-uniform distribution of the SDBD-generated reactive species on the treated surface. Following the indirect plasma treatment by the SDBD reactor, the overall color of pork cut samples after plasma treatment was significantly different compared with before. However, the surface morphology and structural characterization of the treated pork cut samples were not significantly altered, and residual nitrites and nitrates were lower than the restriction level for safe consumption. The SDBD reactor should be developed further to produce a uniform distribution of reactive species on the meat surface for the improvement of the decontamination effect without undesirable effects on meat quality parameters.