Enhancing Post-Harvest Storability of Kale Using Plasma-Sonic Treatment

This study investigated a plasma-sonic treatment that combines plasma-activated water (PAW) and ultrasound (US) as an alternative to conventional sodium hypochlorite (NaOCl), which may leave harmful chlorine residues and generate toxic by-products in fresh produce. The treatment was applied to kale to evaluate its decontamination efficiency and storage stability during 7 days at 4 °C. PAW was generated at 52 W and 14.4 kHz for 624 s, and US was applied at 20 kHz and 250 W for 624 s. The plasma-sonic treatment achieved microbial inactivation of indigenous bacteria by 3.2 log CFU/g, which is comparable to the 3.0 log CFU/g reduction achieved by NaOCl treatment. Moreover, the plasma-sonic treatment group exhibited the highest initial moisture content (89.42%) and maintained higher firmness during storage than the NaOCl-washed and untreated groups. Collectively, these findings indicate that the combined PAW and US washing method constitutes a promising non-chlorine-based intervention that enhances microbial stability while maintaining the physicochemical quality of fresh leafy vegetables.