A novel sensing chip for probing chlorine permeation into simulated produce cracks

Authors: GUAN, YONGGUANG - University Of Maryland; Luo, Yaguang - Sunny; TENG, ZI - University Of Maryland; Zhou, Bin; MEI, LEI - University Of Maryland; Bauchan, Gary; WANG, QIN - University Of Maryland

Submitted to: Advanced Materials Interfaces
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/10/2018
Publication Date: 5/10/2018
Citation: Guan, Y., Luo, Y., Teng, Z., Zhou, B., Mei, L., Bauchan, G.R., Wang, Q. 2018. A novel sensing chip for probing chlorine permeation into simulated produce cracks. Advanced Materials Interfaces. 5(13):119-130.

Interpretive Summary: Washing with sanitizers, such as chlorine, is essential for reducing bacterial populations on fresh fruits and vegetables. While naturally occurring cracks or crevices on the produce are known to reduce the efficacy of bacterial inactivation during washing and sanitizing processes, the lack of a suitable experimental platform for investigating the diffusion of sanitizers as impacted by plant physical features significantly impedes the advancement of science in this important area. In this study, miniaturized chips were three-dimensionally printed and assembled to mimic the cracks on the fresh produce. The chips were furthered coated with chlorine sensing materials and used to evaluate the accessibility of the cracks to chlorine both on the laboratory bench- and during a pilot-scale washing process. The results demonstrated reduced diffusion of chlorine in the cracks than in the solution. Moreover, the diffusion was dependent on the flow rate of the sanitizer solution, as well as the type and dimension of the simulated cracks. This work provides a novel research tool to facilitate investigations of sanitizing efficacy in hard-to-reach areas on the produce during industrial washing processes.

Technical Abstract: Cracks and crevices on fresh produce play important roles on bacteria attachment, and inactivation. A novel chlorine sensing chip was fabricated to probe the diffusing of anti-microbial agent, sodium hypochlorite, through cracks simulated with three-dimensionally printed chips with interlocking design features. The chips were coated with a zein-based film incorporating N,N-diethyl-p-phenylenediamine (DPD) via hydrogen bonding as the chlorine sensing layer. The film improved the affinity of the chip to aqueous hypochlorous acid solution, as evidenced by the reduced contact angle. The chip exhibited a stable, dose-dependent magenta color upon immersion in chlorine solution for 30 s, which allowed the detection of chlorine diffusion at different depths within the cracks. When the chips were exposed to a solution of 72 mg/L free chlorine, fed at constant flow rate of 0.25 or 2.5 m/s, diffusion through the entire crack was observed. During simulated produce washing trial using a pilot-scale washing system, decreased diffusion was detected with increase in crack depth. This work provides a potential experimental platform for studying the accessibility of sanitizers in narrow gaps under various lab- or industry-relevant conditions.