Application of Frozen Plasma-Activated Water to Sanitize and Precool Fresh Produce during Postharvest Handling Process

Converting plasma-activated water (PAW) to frozen PAW (FPAW) imparts additional advantages since it can simultaneously conduct washing, precooling, and decontaminating when incorporated with water. This study investigates the efficacy of FPAW undergoes pH manipulation on decontaminating E. coli and S. aureus inoculated on okra and strawberries surfaces. The effects of dilution factor (3X and 5X dilution), type of PAW (fresh and FPAW), and immersion time (0, 10, 15, and 20 min) on PAW efficacy in combination with the surface properties of okra and strawberries are investigated. Although the reduction achieved by this study was generally lower than the treatment applied to planktonic E. coli and S. aureus , the efficacy of FPAW was not entirely eliminated by the dilution and the surface roughness of the treated product. The reduction of E. coli and S. aureus can be achieved to 2.5 log CFU/g and 1.0 log CFU/g, indicate that pH-manipulated-FPAW has the potential to be applied in the postharvest treatment of fresh produce. In addition, the combination of all treatment factors did not significantly affect the physical quality of the product; in fact, the precooling effects of frozen PAW prevent the chilling injury on okra stored at 4.5 ± 0.5°C for 10 days. Industrial Relevance Conducting precooling with frozen PAW successfully diminishes the problem of chilling injuries and pathogenic bacteria contamination on fresh produce. Converting PAW into the frozen shape and accompanied by pH manipulation overcome the delays issues of the loss of PAW reactivity. The FPAW can be stored longer before it is applied in the precooling and decontamination steps during postharvest treatment. This study shows that FPAW is a potential postharvest treatment agent for fresh produce, and it does not affect the physical quality of the treated fresh produce significantly.