Summary of Awards to Date

Enhancing the efficacy of fresh produce washing operations through establishing monitoring methods and water disinfection technologies based on a combination of filtration and UV.


Jan. 1, 2011 - Dec. 31, 2012

Award Number


Amount Awarded



Keith Warriner, Ph.D.
University of Guelph


The washing of fresh produce is an important step in commercial processing to remove field-acquired contamination. In the course of commercial fresh produce processing the microbial loading and organic loading of the water increases. Consequently, the microbial loading in the water decreases the efficacy of the wash process and increases the potential for contamination to spread through to subsequent product batches. It is common practice to partially or fully replenish tanks with fresh wash water although the timing is largely subjective as opposed to being based on a quality indicator. In the proposed project, a measurable wash water parameter(s) that can be monitored in real time will be identified to report on the microbiological quality. This will enable processors to more accurately identify when the water requires to be changed in order to maintain the efficacy of the wash process and reduce cross contamination events. In addition, a cost effective water-recycling unit will be developed based on a combination of filtration and ultraviolet light. By recycling the efficacy of the wash water process will be maintained with cost savings in resources through reduced consumption and waste-water treatment.   

Technical Abstract

Washing of fresh produce is considered a Critical Control Point despite only limited log count reductions being achieved regardless of the sanitizer applied. However, of more concern is the accumulation of microbial contamination within wash water tanks that ultimately decrease the log count reductions achieved and also leads to extensive cross-contamination events thereby compromising food safety. To maintain wash water quality, tanks can be partially or fully replenished thereby minimizing the accumulation of microbial loading. However, the timing of when to change water in tanks is subjective thereby leading to “good water” being discarded or using the same water for too long. The following proposal will identify wash water parameter(s) (including but not limited to conductivity, turbidity, oxidation-reduction potential or temperature) that can be used to measure the microbiological quality of water in real time. By correlating microbial loading and log count reductions obtained with wash water parameters it will be possible to set critical limits to identify when the wash water should be replenished or replaced. Data will be collected from commercial leafy green processors with sampling trials been undertaken over an entire processing period. A further objective of the study will be to develop a low cost water recycling system based on using filtration in combination with UV Taylor Couette reactor (CT-reactor). The CT-reactor enhances the decontamination efficacy of UV by ensuring efficient mixing in compact unit compatible with high flow-rates. It is estimated that recycling water will save a small-medium sized operation over $200, 000 per year.