Use of a Novel UV-C Tunnel with PAA Misting to Reduce Escherichia coli on Carrots (Daucus carota)

Outbreaks of foodborne illness associated with fresh produce, especially root crops like carrots, represent an ongoing pressing need to develop effective and sustainable methods of decontamination. This study explores a novel decontamination tunnel system to reduce Escherichia coli on whole carrots. The tunnel used four modules of Ultraviolet-C (UV-C) light and sanitizer-spraying nozzles. The evaluations were conducted for the individual intervention as well as combinations of UV-C (254 nm) and Peracetic Acid (PAA) (80 ppm). Based on a randomized controlled trial, four treatment groups were selected: control, treatment with UV-C only, treatment with 80 ppm PAA only, and treatment with combined UV-C and PAA. The test was conducted in three independent trials, with nine replicates per group (n = 9 total). The reductions in microbial loads were expressed as log CFU/g values. Notably, the UV-C combined with PAA treatment produced the greatest mean reduction of 2.83 ± 0.10 log CFU/g, significantly higher than either treated with PAA alone (2.38 ± 0.06 log CFU/g) or UV-C alone (1.49 ± 0.16 log CFU/g) at a p value < 0.0001. The combination of PAA and UV-C light exhibited a complementary effect, meaning the oxidative effect of PAA improved the surface penetration of UV-C, overcoming the limited effectiveness of UV-C in irregular surfaces. This approach has an improved decontamination efficacy on root vegetable surfaces like carrots, which have a rough surface with minute crevices and are difficult to decontaminate through a single treatment. This new tunnel-based technology, combining UV and sanitizer applications, has great potential as an additional second-line strategy to traditional sanitization techniques. Its applications, in addition to enhanced microbial safety of fresh produce and vegetables, also help to decrease the use of chemicals and offer an effective alternative antimicrobial treatment option for organic growers.