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United States Department of Agriculture

Agricultural Research Service

Title: Wash Water Hydro-dynamics and Flow Velocity Affect Escherichia coli O157:H7 Population Reductions on Fruit Surfaces

item Wang, Hua
item Liang, Wei
item Feng, Hao
item Luo, Yaguang - Sunny

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2007
Publication Date: 11/15/2007
Citation: Wang, H., Liang, W., Feng, H., Luo, Y. 2007. Wash Water Hydro-dynamics and Flow Velocity Affect Escherichia coli O157:H7 Population Reductions on Fruit Surfaces. Journal of Food Protection. 70(11):2533-2540.

Interpretive Summary: Recent food-born illness outbreaks associated with the consumption of fresh-cut produce highlight the importance of ensuring food safety of fresh-cut fruits and vegetables. Although produce wash is an important step commonly employed by the industry to maintain the quality and safety of fresh and fresh-cut produce, little scientific information exists as to how wash system design and washing operations affect the reduction of disease-causing microorganisms. This study examined the effect of produce wash parameters, including water flow pattern, velocity, agitation type and rates, as well as contact time, on the reduction of a disease-causing bacterium on the surfaces of cantaloupe rind and cut apples. We found that increasing washing flow velocity and agitation rate significantly promoted the reduction of this bacterium; water agitation over the top of fruit surfaces was more effective to reduce microorganisms than that conducted underneath the fruit samples. This information is important to the produce industry in designing wash systems and wash operations to achieve maximum reduction of disease-causing bacteria and thus to maintain food safety.

Technical Abstract: Washing with sanitizers is an important step to reduce microbial population during produce postharvest processing. Little information exists regarding the effect of hydro-dynamics of wash solution on the efficacy of pathogen reduction. This study was undertaken to investigate effects of washing conditions such as sanitizer flow velocity, agitation rate, and contact time on the reduction of Escherichia coli O157:H7 populations from the surfaces of cantaloupe rind and cut apples. Top surfaces of cylindrical samples were spot inoculated with E. coli O157:H7 and treated with peroxyacetic acid (POAA, 80 mg/L) solutions under different wash patterns, flow velocities, agitation types and rates. Test results indicate that the reduction rate of E. coli O157:H7 increased with the increase in flow velocity and agitation rates; agitation over the top of the fruit surface was more effective on bacterial reduction than the agitation conducted at the bottom of the fruit samples. The experimental data were used to fit different models and it was found that E. coli O157:H7 reduction kinetics from the fruit surfaces was best described by the Weibull model. These finding are important for the design of produce wash systems to achieve enhanced pathogen reduction and improved produce quality and safety.

Last Modified: 06/27/2017
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