Towards the Next-Generation Disinfectant: Composition, Storability and Preservation Potential of Plasma Activated Water on Baby Spinach Leaves

Abstract

Plasma activated water (PAW) has rapidly emerged as a promising alternative to traditional sanitizers applied in the fresh produce industry. In the present study, PAW chemistry and storage stability were assessed as a function of plasma operating conditions. Increasing plasma exposure time (5, 12.5, 20 min) and power (16, 26, 36 W) led to a significant drop in pH (2.4) and higher nitrates and nitrites levels (320 and 7.2 mg/L, respectively) in the PAW. Non-detectable hydrogen peroxide concentration, irrespective of the treatment conditions, was attributed to its instability in acidic environments and the remote PAW generation mode. pH, nitrates and nitrites levels in the PAW remained unaffected after two weeks at 4 °C. The potential of PAW for microbial inactivation and quality retention was demonstrated on baby spinach leaves. Rinsing steps influenced colour development during chilled storage to a greater extent than PAW treatment itself. About 1 log reduction in total bacterial counts (5 log CFU/g) was achieved through PAW rinsing, with no variability after eight days at 4 °C (typical shelf-life at retailers). Moreover, microbial levels on PAW-treated samples after storage were significantly lower than those on control samples, thus contributing to extended product shelf-life and reduced food waste generation.

Plasma-Activated Water (PAW) as a Disinfection Technology for Bacterial Inactivation with a Focus on Fruit and Vegetables

“…In a similar study, the effect of PAW (11 kV for 20 min) on the color (L, a, and b values) of spinach leaves after storage at 4 °C for eight days was compared with the changes in the untreated samples [ 59 ]. The control (untreated) and PAW treated samples showed no significant difference in color evaluated using L, a, and b values, which indicated the “fresh-like appearance”.…”

“…The control (untreated) and PAW treated samples showed no significant difference in color evaluated using L, a, and b values, which indicated the “fresh-like appearance”. It was shown that multiple rinsing with water affected the color as there was an increase in the yellowness (b values), which was not seen with the PAW treated samples [ 59 ]. In another study by Ma et al [ 55 ] using PAW treatment (10 kHz sinusoidal high-voltage source at 18 kV), the change in color and firmness of the treated and untreated strawberries were compared after storage at 20 ± 2 °C and 70 ± 5% RH for four days [ 55 ].…”

Synthesis of Sodium Alginate–Silver Nanocomposites Using Plasma Activated Water and Cold Atmospheric Plasma Treatment

“…It has been widely reported that such an environment is suitable for silver reduction [ 21 ]. A recent application of CP technology is the production of plasma activated water (PAW) through the exposure of water to a CP discharge, e.g., using air as the working gas (creating air plasma), leading to the formation of a combination of reactive oxygen and nitrogen species (RONS) [ 22 ]. PAW is classified neither as a chemical reagent nor a natural resource, but as purified water, which contains a cocktail of reactive oxygen and nitrogen species [ 23 ].…”

The Effect of Using Micro-Clustered Water as a Polymer Medium

“…Moreover, plasma has shown a promising effect in plant growth promotion, pest control, toxin removal, agrochemical dissipation, cancer therapy, tissue regeneration, etc. [3]. However, a few researchers revealed that applying the gas plasma directly over the food surface can cause loss of color and degradation of bioactive compounds [4].…”

“…The antimicrobial activity of MC results from the presence of RONS, which causes damage to the cell membrane, cell wall and DNA, cell shrinkage and cytoplasmic leakage. Some of the studies have focused on the use of MC as a plant disinfectant [3], food disinfectant [9][10][11], and inducer for plant growth [12].…”