Efficacy of sumac and oregano in the inactivation of Salmonella Typhimurium on tomatoes

The antimicrobial efficacy of sumac (Rhus coriaria L.) water extracts (1%, 3% and 4%) and oregano (Oreganum onites) oil suspensions (25 ppm, 75 ppm and 100 ppm) was tested against the nalidixic acid resistant strain of Salmonella Typhimurium ATCC 13311 inoculated to tomatoes. The inoculated tomatoes (2.71–4.35 log cfu/tomato) were subjected to treatment for 5, 10, 15 and 20 min by washing with sterile distilled water (control), sumac extracts or oregano oil suspensions with or without rinsing in sterile distilled water. Treatment of tomatoes with sumac and oregano caused significant reductions in S. Typhimurium population compared to the control (P < 0.05). However, there was no significant difference between washing times in the reduction of S. Typhimurium (P > 0.05). The maximum logarithmic reductions of S. Typhimurium were obtained at levels of 2.38 and 2.78 logarithmic units on tomatoes treated with 4% sumac extract and 100 ppm oregano, respectively. No statistical difference was obtained in the number of S. Typhimurium recovered in different concentrations of treatment solutions in four different treatment times (P > 0.05). The results suggest that the use of sumac water extract or oregano oil suspensions can be used to enhance microbial safety of tomatoes without loss in quality attributes.