Summary of Awards to Date

Validation of chlorine level in sanitization system to avoid cross-contamination


Jan. 1, 2015 - Dec. 31, 2016

Amount Awarded



Qin Wang, Ph.D.
University of Maryland


Scientifically validated data are needed by regulators and commercial fresh-cut processors to determine the minimum chlorine concentration required to prevent pathogen cross-contamination in produce wash waters. This project will address this issue by development of a microfluidic mixer that simulates cross-contamination and pathogen survival scenarios in chlorinated produce wash water. The microfluidic mixer has the unique capability of manipulating solutions at a miniaturized scale within instantaneous response times. Thus, the mixer will provide a technological solution to the limitations encountered in macroscale testing. This project will investigate the relationship between contact time (0.1 second – 5 minutes) and chlorine level (0.125 to 50 ppm) to prevent cross-contamination in wash water. Minimal contact times for given chlorine levels will be determined for planktonic and biofilms of bacterial cells. Results will be further validated using industrial produce wash water to investigate the effects of operational variables (pH, temperature, organic load) on the contact time requirement at different chlorine levels. We anticipate the proposed study will provide insight on the relationship between minimal contact time and chlorine level, and therefore predict the processing requirement at given variables to effectively prevent cross-contamination in wash water.

Technical Abstract 

It is important to determine the minimum chlorine concentration that results in the inactivation of pathogens quickly enough to avoid cross-contamination. This proposal addresses several needs by industry, specifically: 1) Development of a novel contact time x chlorine dose-sensitive method and response curves to determine the conditions needed to prevent cross-contamination by planktonic and biofilm E. coli O157:H7 and Salmonella in the presence of organic matter loads during fresh-cut wash water operations; 2) Identify salient operational variables for measuring the performance of hypochlorous acid wash water sanitizer for fresh-cut operations.

Key features of this proposal include a microfluidic mixing device to simulate possible cross-contamination and pathogen survival scenarios in hypochlorous acid wash water; determination of contact time (0.1 second to 5 minutes) and chlorine dose (0.25 to 50 ppm) to prevent cross-contamination of planktonic cells and biofilm. The results will assist fresh produce industry and governmental agencies in the development of effective sanitization practices to prevent cross-contamination in wash water, and advance the safety and quality of fresh leafy green produce post-harvest sanitization.