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Natural surface coating to inactivate Salmonella enterica serovar Typhimurium and maintain quality of cherry tomatoes

Juan Yun, Xuetong Fan, Xihong Li, Tony Z. Jin, Xiaoyu Jia, James P. Mattheis
International journal of food microbiology 2015 v.193 pp. 59-67
cherry tomatoes, mustard oil, detection limit, postharvest technology, coatings, Salmonella Typhimurium, food quality, cinnamon oil, food microbiology, storage time, firmness, color, mutants, storage, zein, cinnamon, weight loss, waxes, food safety, ascorbic acid
The objective of the present study was to investigate the effectiveness of zein-based coatings in reducing populations of Salmonella enterica serovar Typhimurium and preserving quality of cherry tomatoes. Tomatoes were inoculated with a cocktail of S. Typhimurium LT2 plus three attenuated strains on the smooth skin surface and stem scar area. The zein-based coatings with and without cinnamon (up to 20%) and mustard essential oil or a commercial wax formulation were applied onto tomatoes and the treated fruits were stored at 10°C for up to 3weeks. Populations of S. Typhimurium decreased with increased essential oil concentration and storage duration. S. Typhimurium populations on the smooth skin surface were reduced by 4.6 and 2.8logcolonyformingunits(CFU)/g by the zein coatings with 20% cinnamon and 20% mustard oil, respectively, 5h after coating. The same coating reduced populations of S. Typhimurium to levels below detection limit (1.0logCFU/g) on the stem scar area of tomato during 7days of storage at 10°C. Salmonella populations were not reduced on fruit coated with the commercial wax. All of the coatings resulted in reduced weight loss compared with uncoated control. Compared with the control, loss of firmness and ascorbic acid during storage was prevented by all of the coatings except the zein coating with 20% mustard oil which enhanced softening. Color was not consistently affected by any of the coating treatments during 21days of storage at 10°C. The results suggest that the zein-based coating containing cinnamon oil might be used to enhance microbial safety and quality of tomato.