Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/21/2015
Publication Date: 4/1/2015
Publication URL: http://handle.nal.usda.gov/10113/61032
Citation: Mukhopadhyay, S., Ukuku, D.O., Juneja, V.K. 2015. Effects of different combined non-thermal treatments against Salmonella enterica on plum tomatoes. Food Control. 56:147-154. DOI: 10.1016/j.foodcont.2015.03.020.
Interpretive Summary: Consumption of fresh fruit and vegetables are encouraged due to health reasons. Tomatoes provide multiple health benefits. However, tomatoes are one of the major contributors to produce-related outbreaks. Existing chlorine based washing raised serious public health concern. Also effectiveness of chlorine based washing is limited in the presence of organic load, for pathogens in biofilm and for internalized pathogens. Hence there is a serious need for safe and effective alternate technologies to chlorine based processing. The purpose of present study was to evaluate the synergistic effect of different combined non-thermal treatments based on ultraviolet light and various sanitizer formulations against food borne pathogens like Salmonella and natural spoilage organisms such as bacteria, yeast and molds on tomato.
Technical Abstract: Produce contamination by foodborne pathogens remains a serious threat. This study investigated synergistic effects of ultraviolet-C and various active sanitizers’ washes against Salmonella enterica on plum tomatoes. A bacterial cocktail containing three serotypes of Salmonella enterica (S. Newport H1275, S. Stanley H0558, and S. Montevideo G4639) was used to prepare the inoculums. Tomatoes were spot inoculated using approximately 100 microliters of inocula to achieve a population of about 7 log CFU/tomato. An inoculated tomato was initially treated with a low dose (0.6 KJ per sq. meter) of UV-C light (253.7 nm) followed by immersing in selected sanitizing solution (700 mL) to wash under mild agitation (ca. 250 rpm) for 2 min at room temperature (22 degree C). Inactivation efficacy of combined treatments varied widely depending on the sanitizer property. Combined UV-C plus aqueous ozone (1 ppm) provided 3.13 log CFU/fruit Salmonella reduction which was significantly lower (p less than 0.05) compared to the rest of the combination treatments; whereas the treatment of UV-C followed by wash in a new antimicrobial preparation ‘HEN’, formulated mixing hydrogen peroxide, EDTA and nisin provided the best log reduction (4.71 log CFU/fruit). Organic acids (1%) or their binary mixtures (2%), hydrogen peroxide (3%), and HEN provided greater than 4.0 log reductions for UV-C treated tomatoes. Treatments were effective in controlling native microbial loads as the total aerobic mesophilic organisms and the population of yeast and mold remained significantly (p less than 0.05) low during storage compared to control. Findings from this study provide safe and effective post harvest chemical decontamination techniques as an alternative to chlorine based wash for produce industry, specifically for tomato processors. These results may also help researchers design future decontamination studies.