Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/3/2013
Publication Date: 4/1/2014
Citation: Zhou, B., Luo, Y., Nou, X., Millner, P.D. 2014. Development of a feed-forward sodium hypochlorite dosing scheme to maintain stable free chlorine concentration during simulated produce wash operations. Journal of Food Protection. 77:558-566.
Interpretive Summary: Chlorine is widely used by the fresh and fresh-cut produce industry to prevent pathogen survival and spread during produce wash operations. However, free chlorine is rapidly depleted during produce wash, resulting in a significant increase in food safety risks. In this study, a feed-forward dosing mechanism for free chlorine control was developed, and further validated, under simulated fresh-cut produce washing operations. Targeted free chlorine concentration was maintained in the wash solution in the presence of increasing organic load typically typical of the produce wash environment. Application of this technology will lead to improved process control for free chlorine concentration and therefore reduced pathogen cross-contamination risks during the commercial fresh-cut wash operations. This information should be very useful for the fresh-cut produce industry.
Technical Abstract: Chlorine is widely used by the fresh and fresh-cut produce industry to prevent pathogen survival and spread during produce wash operations. However, rapid accumulation of organic material in the wash solution (from cutting and other processing steps) results in accelerated loss of free chlorine and concomitant increase in food safety risk as a result of this depletion. Therefore, developing techniques to maintain adequate free chlorine concentration during commercial-scale produce washing, given the rapid surges in organic load, is a critical food safety objective for reducing microbiological risks associated with the consumption of fresh and fresh-cut produce. This study reports the results of an effort to use "breakpoint chlorination" analysis to develop a programmed dosing system to maintain relatively stable chlorine concentration in the presence of increasing organic material in a produce washing system. Tomato extract was used to simulate the organic load resulting from repeated addition of produce to a washing system. Experimental results indicate that a combined chlorine hump and a chlorination breakpoint exist during simulated produce washing. The dosages of sodium hypochlorite required to reach the combined chlorine hump and breakpoint were linearly correlated with the organic load. The relationship between free chlorine and organic load was established, and was used to develop a feed-forward chlorine dosing algorithm to control free chlorine levels by continually adjusting the sodium hypochlorite addition rate during recurrent addition of organic load. The results from a series of laboratory trials indicated that free chlorine can be maintained at targeted levels using such an algorithm. The pH and ORP were also maintained at stable values by the feed-forward chlorine dosing scheme.