Efficacy of Produce Wash Product: Use of Fresh Potatoes as Model System for Evaluating Pathogen Control in Produce Processing Peter Gray, Dong-Hyun Kang. Department of Food Science and Human Nutrition, Washington State University, Pullman, WA Jeff Kronenberg. Department of Food Science & Toxicology, University of Idaho, Moscow, ID

Foodborne Illness in the USA (Source: CDC) 76 million illnesses every year Results in 300,000 hospitalizations Causes 5,000 deaths Increasing incidence of STEC O157 infections traced to fresh produce, while those related to meats decreasing

Outbreak-Associated Cases of Foodborne Illness (CDC) STEC O157 outbreak (32 confirmed cases) traced to spinach 2 STEC O157 outbreaks (14 confirmed cases) traced to lettuce Multistate outbreak of Salmonella Typhimurium (58 confirmed cases) traced to tomatoes Outbreak of Salmonella Newport (37 confirmed cases) traced to tomatoes

Escherichia coli O157:H7 Outbreak traced to raw spinach from Salinas Valley, California, cases in 26 states (CDC)

Salmonella Typhimurium Outbreak traced to tomatoes, 183 cases in 21 states, 2006 (FDA)

Bacterial Soft Rot of Potatoes Caused by Gram-negative bacterium Pectobacterium carotovorum ssp. carotovorum (formerly classified as Erwinia cartovora ssp. carotovora)Caused by Gram-negative bacterium Pectobacterium carotovorum ssp. carotovorum (formerly classified as Erwinia cartovora ssp. carotovora) Dissolves middle lamella (intercellular cement), causing vegetables to liquifyDissolves middle lamella (intercellular cement), causing vegetables to liquify

Search for Effective Produce Sanitizers Must be effective in wash flumes and dip tanks under a wide variety of water conditions Increasing consumer demand for effective but safe, “natural”, “environmentally- friendly” disinfectants

HealthPro Brands FIT® Fruit and Vegetable Wash Produce cleaner and antibacterial agent Ingredients: citric acid, sodium lauryl sulfate, grapefruit oil extract, sodium carbonate. All FDA GRAS. Very safe and easy to store, handle, and prepare; available to general public Used at pH 3.0; 5 g/L powdered formulation, 1:128 (v:v) liquid formulation WSU Sensory panel detected no off-flavors in FIT-treated baked potatoes

Chlorine Dioxide (ClO 2 ) Approved for use on fresh fruits and vegetables Hazardous ingredients (sodium chlorite, hydrochloric acid, sodium hypochlorite) Hazardous to store and prepare Personal protective gear required Commonly used at 5 ppm free ClO 2 ClO 2 produces no toxic by-products or off-flavors in produce

FIT Testing Protocol – Fresh Pack Potato Operation Assay for aerobic plate count (bacterial microflora) and Gram negative bacteria (indicator of enteric human pathogens and Pectobacterium soft rot) Flume washed potatoes – powdered FIT, untreated water control Spray bar treated potatoes – liquid FIT, 9 ppm ClO 2, untreated water control

Reduction of Gram Negatives, APC in Fresh Pack Potato Tubers

Reduction of Gram Negatives, APC in Fresh Pack Potato Flume Water

Sanitizer Evaluations Utilizing Bacterial Suspensions in Vitro Chemicals: powdered FIT, liquid FIT, 9 ppm ClO 2, water control Chemicals: powdered FIT, liquid FIT, 9 ppm ClO 2, water control Bacteria suspended in treatment solutions, enumerated at selected intervals Bacteria suspended in treatment solutions, enumerated at selected intervals E. coli O157:H7, S. Typhimurium, P. carotovorum ssp. carotovorum tested E. coli O157:H7, S. Typhimurium, P. carotovorum ssp. carotovorum tested Both deionized and potato flume water evaluated Both deionized and potato flume water evaluated

Reduction of Escherichia coli O157:H7 in Vitro Using Deionized Water Treated With Sanitizers

Reduction of Salmonella Typhimurium in Vitro Using Deionized Water Treated with Sanitizers

Reduction of Pectobacterium carotovorum ssp. carotovorum in Vitro Using Deionized Water Treated with Sanitizers

330 mg/L total dissolved solids 2,186 mg/L total suspended solids Water containing soil particles, potato tissues present serious challenges to sanitizers In Vitro Trials Using Sterile Flume Water From Fresh Pack Potato Operation Flume water (left), deionized (right)

Reduction of Escherichia coli in Vitro Using Flume Water Treated with Sanitizers

Reduction of Salmonella Typhimurium in Vitro Using Flume Water Treated with Sanitizers

Reduction of Pectobacterium carotovorum ssp. carotovorum in Vitro Using Flume Water Treated with Sanitizers

Tests on Inoculated Potato Tubers E. coli O157:H7, S. Typhimurium inoculated onto unwashed tubers and dried Treatments prepared with flume water Tubers agitated in treatment solutions, removed at selected intervals, enumerated Treatments FIT (powdered and liquid formulations) 9 ppm ClO 2 Flume water control

Reduction of Escherichia coli O157:H7 on Inoculated Potatoes

Reduction of Salmonella Typhimurium on Inoculated Potatoes

Tests on Uninoculated Potato Tubers Unwashed, uninoculated tubers agitated in treatment solutions, removed at selected intervals, enumerated Aerobic Plate Count (APC) Yeasts Molds

APC of Uninoculated Potato Tubers in Flume Water Treated With Sanitizers

Yeast Microflora of Uninoculated Potato Tubers in Flume Water Treated With Sanitizers

Mold Microflora of Uninoculated Potato Tubers in Flume Water Treated With Sanitizers

Conclusions – Potato Wash Water FIT highly effective (>6 log reduction in 30 sec) against cell suspensions of enteric pathogens and P. carotovorum ssp. carotovorum under all water conditions tested Limited APC reduction, possibly due to acid- resistant yeasts and molds ClO 2 effective only in low solids water FIT has significant potential for preventing cross- contamination of pathogens in flumes and dip tanks with high soil loading

Conclusions – Potato Tuber Tests Low impact from both disinfectants In lab tests FIT reduced enteric pathogens by log but only after 5 min; ClO 2 resulted in <0.9 log reduction In lab tests FIT reduced APC, yeasts, molds by 0.8 – 1.2 log; ClO 2 was no more effective than water control Potato tubers represent challenges due to heavy soils, lenticels, other surface features More research needed involving other vegetable models

Acknowledgements Todd Wichmann, HealthPro Brands, Inc. of Cincinnati, Ohio Wada Farms Marketing Group, LLC. Of Pingree, Idaho International Dioxide, Inc. of North Kingstown, Rhode Island