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United States Department of Agriculture

Agricultural Research Service

Title: Decay kinetics of free chlorine in fresh produce wash system

item Zhou, Bin
item Feng, Hao
item Luo, Yaguang - Sunny

Submitted to: Annual Meeting of the Institute of Food Technologists
Publication Type: Abstract Only
Publication Acceptance Date: 3/14/2008
Publication Date: 6/26/2008
Citation: Zhou, B., Feng, H., Luo, Y. 2008. Decay kinetics of free chlorine in fresh produce wash system. Annual Meeting of the Institute of Food Technologists.

Interpretive Summary:

Technical Abstract: Chlorinated water wash is a critical step employed in the production of fresh-cut produce. The efficacy of chlorinated water was affected largely by the concentration of active chlorine ingredients, which degrades due to the presence of microorganisms, as well as inorganic and organic matters. It is important to investigate the kinetics of chlorine decay under different operation conditions. The objective of this study was to examine the effect of different treatment conditions on the concentration of chlorine during washing of fresh-cut produce. Washing tests were conducted at 4 degree C in a 1-L jacketed beaker placed on a stir plate. The washing solution was prepared by adding a commercial sanitizer of Chlorox (6.15% active ingredient) to distilled water. Romaine lettuce inner layer slices (1.0×1.0 inch) were submerged in 700 ml of 200 ppm chlorinated water, and washed for 4 min with or without agitation at 300 rpm. The produce-to-solution ratio was 1/5, 1/10, and 1/20 g/mL. Samples of the washing solution were taken at 0, 0.5, 1, 2, and 4 min, and examined for the concentration of free and total chlorine. The concentration reduction rate (ppm/min) of both free chlorine and total chlorine followed a first order kinetic model for samples washed with and without agitation at all three produce-to-solution ratios. The effect of produce-to-solution ratio on chlorine decay (ppm/min) was also characterized by a semi-log relation. The effect of agitation was found to be not important in this study. Under the experimental conditions used in this study, the sample-to-solution ratio was an important factor affecting the decay of chlorine in washing solutions. The chlorine decay models will help to improve washing system design and selection of operational conditions.

Last Modified: 06/25/2017
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