Spray washing of tomatoes with chlorine dioxide to minimize Salmonella on inoculated fruit surfaces and cross-contamination from revolving brushes.

Abstract

Chlorine dioxide (ClO(2)) is an antimicrobial agent available for commercial produce washing. This study examined the efficacy of ClO(2) at 5 parts per million (ppm) during spray washing of tomatoes (5.0 ml/s per fruit) for preventing Salmonella enterica transfer from inoculated roller brushes to fruit and wash runoff. Furthermore, the sanitizing effects of ClO(2) during spray washing at low and high flow rates (5.0 and 9.3 ml/s per fruit, respectively) on tomato surfaces (nonstem scar areas) with either newly introduced (wet) or overnight air-dried Salmonella inocula were investigated. Salmonella transfer from contaminated brushes to fruit surfaces was reduced 2.1 +/- 0.6 or 4.7 +/- 0.2 log cycles after spray washing with water for 40 s or with the ClO(2) solution for 10 s, respectively. Cross-contamination of Salmonella from brushes to wash runoff during fruit washing for 60 s decreased 5.9 +/- 0.3 log cycles when ClO(2) was used. Fruit washing using contaminated brushes and low flow-rate washing with either water or ClO(2) solution for 10 s reduced newly introduced Salmonella on fruit surfaces by 1.7 +/- 0.6 or 5.1 +/- 0.3 log cycles, respectively. For fruit surfaces with air-dried inocula, washing with water and using uncontaminated brushes for 10 to 40 s reduced Salmonella by 3.2 +/- 0.3 to 3.4 +/- 0.4 log cycles; and the reduction was significantly improved by using ClO(2), high flow rate, or a longer washing time. Washing with ClO(2) at tested flow rates for 10 to 60 s resulted in a 4.4 +/- 0.6 to 5.2 +/- 0.1 log reduction of air-dried Salmonella on fruit surfaces.