Combined sanitizer treatments help eliminate Salmonella risk.

University of Florida scientists wanted to increase the efficiency of postharvest treatments against Salmonella found on tomatoes. So, they used treatments consisting of 220 ppm of sodium hypochlorite (HOCl), 1,200 ppm of acidified sodium chlorite (ASC), 80 ppm of peroxyacetic acid (PAA) and chlorine dioxide gas (Cl[O.sub.2]). It turns out that a combination of treatments, with three consecutive intervention steps, is most effective at minimizing the risk of Salmonella contamination on tomatoes.

Aqueous sanitizer treatments were performed in a simulated flume with different exposure times of up to 120 seconds. Researchers performed the gas phase Cl[O.sub.2] treatment in a pressure vessel for 1 hour. Combined treatments were performed by immersing the product in HOCl, then in ASC, after which the product underwent a Cl[O.sub.2] gas phase treatment.

Investigators inoculated each tomato with a five-strain cocktail of Salmonella, placing the bacteria on artificially created wounds, smooth surfaces and stem scar tissue. A second set of each of the sample groups was stored at 20 C and 95% relative humidity. These were retested after 5 days.

All aqueous sanitizer treatments caused a greater than 5-log unit reduction of Salmonella inoculated on the smooth surface of the tomatoes. No Salmonella was recovered after storing the products for five days. All aqueous treatment groups showed greater than a 1.0-log unit reduction, and greater than a 2.0-log unit reduction, in stem scar and puncture wounds for the 120-second treatment, respectively.

The Cl[O.sub.2] treatment decreased the number of Salmonella to undetectable levels in the stem scars. But no reduction was observed in puncture wounds after 1 hour of contact time. The combined treatment also completely inactivated Salmonella in stem scars and achieved a 3-log unit reduction of bacteria in puncture wounds. In all cases, the puncture wounds experienced an increase in recovered Salmonella numbers after undergoing five days of storage. Further information. Keith Schneider, Department of Food Science and Human Nutrition, University of Florida, 359 FSHN Building, Newell Drive, P.O. Box 110370, Gainesville, FL 32611; phone: [phone]; fax: [phone]; email: [e-mail].