Application of Plasma Activated Fine Bubble Water on Fresh-Cut Lettuce Quality and Safety

Abstract

Lettuce (Lactuca sativa L.) is highly susceptible to postharvest deterioration, microbial contamination, and pesticide residues. This study evaluated the effectiveness of plasma-activated water (PAW) and plasma-activated fine bubble water (PAFBW) compared to distilled water (control) in maintaining the quality and safety of fresh-cut lettuce. A completely randomized design evaluated four factors: ozone concentration (1 and 2 ppm), immersion time (1 and 2 min), washing solution type (PAW and PAFBW), and storage temperature (15 °C and 25 °C). Distilled water controls were analyzed separately. Weight loss and total color difference (ΔE) were evaluated after two days of storage. Total plate count (TPC), total phenolics, and qualitative pesticide screening were measured immediately after washing and analyzed descriptively. One-Way ANOVA showed highly significant overall treatment effects (p<0.001) on weight loss (F=10.90) and color change (F=61.94). Factorial GLM identified storage temperature as the dominant factor. The 2 ppm PAW treatment with 2-min immersion at 15 °C produced the lowest weight loss (0.87 ± 0.11%) and smallest total color difference (0.40 ± 0.04). The lowest TPC was obtained for PAW 2 ppm 2 min (17,000 colony-forming units per gram [CFU/g]) and PAFBW 2 ppm 2 min (19,950 CFU/g). The highest total phenolic content was found in PAW 1 ppm 2 min (6.98 ± 0.05 mg gallic acid equivalents per gram [mg GAE/g]). PAW generally outperformed PAFBW in quantitative parameters, while PAFBW yielded the most favorable qualitative pesticide screening response, highlighting plasma technology's postharvest potential.