Chlorine Disinfection of Tomato Surface Wounds Contaminated with Salmonella spp.

Abstract

This study examined the efficacy of chlorine treatments of flume water for eliminating Salmonella spp. from inoculated wounds and intact surfaces of tomatoes (Lycopersicon esculentum). Water in a scale-model flume was chlorinated to 150 mg·L-1 of free chlorine at pH 6.5 and maintained at a temperature of 25 or 35 °C, depending on the test. Viable Salmonella were recovered from all of the inoculation sites (intact fruit surface, punctures, shaves, and stem scars) even after treatment with chlorinated water for up to 120 seconds at either 25 or 35 °C. Generally, the highest Salmonella recovery came from puncture wounds and the lowest from the intact surfaces. After 120 seconds at 25 °C, 4.9 to 5.8 log10 units were recovered from the wounds. Populations recovered after the 30-second treatment at 35 °C ranged from 4.1 log10 cfu/mL for intact surfaces to 6.0 log10 cfu/mL in the puncture wounds. At 60- and 120-second treatment times, all wounds had higher mean populations than tomatoes with intact surfaces. Although greater Salmonella survival was associated with shorter exposure to the chlorine, water chlorination cannot completely eliminate contamination of tomato fruit by Salmonella, even on intact surfaces. Stem scars, in this study, were not readily disinfected with sodium hypochlorite.