Dielectric barrier discharge plasma for microbial decontamination of dried laver: effects on physicochemical characteristics

Inhibitory effects of atmospheric dielectric barrier discharge plasma against Bacillus cereus and Staphylococcus aureus on Gwamegi (Semi-dried Cololabis saira)

AIMS

The current study was conducted to investigate the effects of atmospheric dielectric barrier discharge (DBD) plasma on the reduction of B. cereus and S. aureus, both potential hazardous bacteria on Gwamegi.

METHODS AND RESULTS

DBD plasma devices (1.1 kV, 43 kHz, 5-60 min, N₂ : 1.5 lpm for 5, 10, 20, 30 and 60 min) were used to investigate the reduction effect. In the B. cereus by DBD plasma treatment, the 5-60 min indicated a reduction of 0.2-1.2 log CFU/g. The reductions of S. aureus at the same duration time of DBD plasma were 0.1-1.1 log CFU/g. The D-values for B. cereus and S. aureus were 49.0 (R² =0.98) and 61.0 (R² =0.94) min respectively. The pH values for 0-30 min (6.00-6.01) were not significantly different, but significant differences at 60 min (6.09). There were no significant sensorial differences in color (6.4-5.2) and flavor (6.2-5.3), but showing significant differences in appearance (6.6-5.2), texture (6.3-5.1), and overall acceptability (6.5-5.5).

CONCLUSIONS

This study indicates that the 60 min of DBD plasma treatment resulted in > 1 log CFU/g of B. cereus and S. aureus without concomitant adverse changes of pH and most sensory properties in semi-dried Gwamegi.

SIGNIFICANCE AND IMPACT OF THE STUDY

This novel DBD plasma technology can be applied in semi-dried food production and distribution processes to enhance dried fishery food hygiene and safety.

Dielectric barrier discharge cold atmospheric plasma: Influence of processing parameters on microbial inactivation in meat and meat products

Decontamination of meat is commonly practiced to get rid of or decrease the microbial presence on the meat surface. Dielectric barrier discharge cold atmospheric plasma (DBD-CAP) as innovative technology is a food microbial inactivation technique considered in high regard by food scientists and engineers in present times. However, cold atmospheric plasma application is at the experimental stage, due to lack of sufficient information on its mode of action in inactivating microbes, food shelf-life extensibility, whereas, the nutritional value of food is preserved. In this review, we have appraised recent work on DBD-CAP concerning the decontamination treatment of meat products, highlighting the processing value results on the efficacy of the DBD-CAP microbial inactivation technique. Also, the paper will review the configurations, proposed mechanisms, and chemistry of DBD-CAP. Satisfactory microbial inactivation was observed. In terms of DBD-CAP application on sensory evaluation, inferences from reviewed literature showed that DBD has no significant effect on meat color and tenderness, whereas in contrast, TBARS values of fresh and processed meat are affected. DBD seems economically efficient and environmentally sustainable.

Virucidal Effects of Dielectric Barrier Discharge Plasma on Human Norovirus Infectivity in Fresh Oysters (Crassostrea gigas)

This study investigates the effects of dielectric barrier discharge (DBD) plasma treatment (1.1 kV, 43 kHz, N2 1.5 L/min, 10~60 min) on human norovirus (HuNoV) GII.4 infectivity in fresh oysters. HuNoV viability in oysters was assessed by using propidium monoazide (PMA) as a nucleic acid intercalating dye before performing a real-time reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Additionally, the impact of the DBD plasma treatment on pH and Hunter colors was assessed. When DBD plasma was treated for 60 min, the HuNoV genomic titer reduction without PMA pretreatment was negligible (<1 log copy number/µL), whereas when PMA treatment was used, HuNoV titer was reduced to >1 log copy number/µL in just 30 min. D1 and D2-value of HuNoV infectivity were calculated as 36.5 and 73.0 min of the DBD plasma treatment, respectively, using the first-order kinetics model (R2 = 0.98). The pH and Hunter colors were not significantly different (p > 0.05) between the untreated and DBD-plasma-treated oysters. The results suggest that PMA/RT-qPCR could help distinguish HuNoV infectivity without negatively affecting oyster quality following >30 min treatment with DBD plasma. Moreover, the inactivation kinetics of nonthermal DBD plasma against HuNoV in fresh oysters might provide basic information for oyster processing and distribution.

The Efficiency of Atmospheric Dielectric Barrier Discharge Plasma against Escherichia coli and Bacillus cereus on Dried Laver (Porphyra tenera)

This study investigated the effects of atmospheric dielectric barrier discharge (DBD) plasma (1.1 kV, 43 kHz, 5–30 min, N₂: 1.5 L/m) on the reduction of Escherichia coli and Bacillus cereus on dried laver. The reductions of E. coli and B. cereus by 5, 10, 20, and 30 min of DBD plasma were 0.56 and 0.24, 0.61 and 0.66, 0.76 and 1.24, and 1.02 and 1.38 log CFU/g, respectively. The D-value of E. coli and B. cereus was predicted as 29.80 and 20.53 min, respectively, using the Weibull model for E. coli (R² = 0.95) and first-order kinetics for B. cereus (R² = 0.94). After DBD plasma 5–30 min treatment, there was no change in pH (6.20–6.21) and this value was higher than the untreated dried laver (6.08). All sensory scores in DBD plasma-treated laver were determined as >6 points. The 30 min of DBD plasma is regarded as a novel intervention for the control of potential hazardous bacteria in dried laver.

Factors influencing the antimicrobial efficacy of Dielectric Barrier Discharge (DBD) Atmospheric Cold Plasma (ACP) in food processing applications

Atmospheric cold plasma (ACP) is an emerging technology in the food industry with a huge antimicrobial potential to improve safety and extend the shelf life of food products. Dielectric barrier discharge (DBD) is a popular approach for generating ACP. Thanks to the numerous advantages of DBD ACP, it is proving to be successful in a number of applications, including microbial decontamination of foods. The antimicrobial efficacy of DBD ACP is influenced by multiple factors. This review presents an overview of ACP sources, with an emphasis on DBD, and an analysis of their antimicrobial efficacy in foods in open atmosphere and in-package modes. Specifically, the influence of process, product, and microbiological factors influencing the antimicrobial efficacy of DBD ACP are critically reviewed. DBD ACP is a promising technology that can improve food safety with minimal impact on food quality under optimal conditions. Once the issues pertinent to scale-up of plasma sources are appropriately addressed, the DBD ACP technology will find wider adaptation in food industry.