Submitted to: International Journal of Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 8, 2012
Publication Date: July 16, 2012
Citation: Luo, Y., Nou, X., Millner, P.D., Zhou, B., Shen, C., Yang, Y., Wu, Y., Wang, Q., Fen, H., Shelton, D.R. 2012. A pilot plant scale evaluation of a new process aid for enhancing chlorine efficacy against pathogen survival and cross-contamination during produce wash. International Journal of Food Microbiology. 158(2):133-139.
Interpretive Summary: Chlorine-containing disinfectants are widely used by the fresh produce industry in wash waters to substantially reduce the microbial content of the water in order to reduce the potential for contamination of the produce by post-harvest disease agents and/or human pathogens. The disinfectant efficacy of chlorine in wash solutions depends on several factors, including pH, organic matter content, temperature, and the concentration of hypochlorous acid (the active sanitizing agent form of chlorine), in the wash water. When large amounts of organic matter are introduced into chilled process wash water, the active chlorine concentration decreases rapidly, because the hypochlorous acid oxidizes the organic matter (produce tissue, juices, and solids). The rapid chlorine decrease results in microbial survival in the wash solution and the potential spread of microbes to uncontaminated produce. In this study, we investigated the effect of a novel, commercially-available produce wash aid on reducing survival and spread of E. coli O157:H7 during semi-commercial scale pilot-plant wash operation. Our results indicate that this new process wash aid significantly reduced the potential for E. coli O157:H7 to survive in the wash solution and to spread to uncontaminated shredded lettuce. Application of this novel wash aid in a chlorine-based fresh produce sanitization system could increase the safety margin of process control on commercial fresh-cut wash operations.
This information will be useful to other researchers, regulatory industries and the produce industry.
Developing food safety intervention technology that can be readily adopted by the industry often requires test conditions that match as closely as possible to those of commercial food processing operations; yet biosafety risks inherent in pathogen studies constrain most experiments to laboratory settings. In this study, we report the first semi-commercial pilot-scale evaluation of a new process aid, T128, for its impact on enhancing the antimicrobial efficacy of chlorinated wash water against pathogen survival and cross-contamination. A non-pathogenic, BSL-1, strain of E. coli O157:H7 was inoculated onto freshly harvested baby spinach leaves and washed with large amounts of freshly cut un-inoculated iceberg lettuce shreds in chlorinated wash water, in the presence or absence of T128. The use of T128 did not significantly (P > 0.05) influence the rate of wash water deterioration, particularly the increase of organic matter accumulation or the decrease in free chlorine levels, during washing. However, in the absence of T128 (Control), survival of E. coli O157:H7 in wash water and cross-contamination of un-inoculated lettuce frequently occurred when free chlorine in solution dropped below 1 mg/L during the wash process. In contrast, use of T128 significantly reduced the occurrence of E. coli O157:H7 surviving in wash water and of cross-contamination to un-inoculated shredded iceberg lettuce under the same operational conditions. No significant difference was observed in E. coli O157:H7 populations remaining on spinach leaves after washing in chlorinated water in the presence or absence of T-128. Although the mechanism of the synergistic interaction between T128 and free chlorine is still unclear, application of this novel wash aid in a chlorine-based fresh produce sanitization system could increase the safety margin of process control on commercial fresh-cut operations.