Survival of foodborne pathogens on commercially packed table grapes under simulated refrigerated transit conditions

Authors: Carter, Michelle; FENG, DORIS; Chapman, Mary; GABLER, FRANKA - CALIFORNIA TABLE GRAPE COMMISSION

Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/6/2017
Publication Date: 12/9/2017
Citation: Carter, M.Q., Feng, D., Chapman, M.H., Gabler, F. 2017. Survival of foodborne pathogens on commercially packed table grapes under simulated refrigerated transit conditions. Food Microbiology. 72:199-205. https://doi.org/10.1016/j.fm.2017.12.004.
DOI: https://doi.org/10.1016/j.fm.2017.12.004

Interpretive Summary: Sulfur dioxide fumigation is an effective way to control fungal infections and to prevent decay during table grape storage. To preserve quality of postharvest table grapes during long-distance export marketing or long retail handling in which sulfur dioxide fumigation cannot be applied, the use of in-package sulfur dioxide-generating pads is a common practice by table grape industries worldwide. In this study, we determined the antimicrobial activity of sulfur dioxide-generating pads on three common foodborne pathogens, Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella enterica Thompson under simulated in-transit conditions. We found that L. monocytogenes was highly sensitive to cold temperature alone and also highly susceptible to a slow sulfur dioxide release pad. E. coli O157:H7 had the highest tolerance to cold temperature and to the sulfur dioxide pad. The S. enterica Thompson strain displayed similar cold survival fitness as the L. monocytogenes strain, but was much more sensitive to cold alone than E. coli O157:H7 strain and more resistant to the sulfur dioxide pad than the L. monocytogene strain. Use of a slow release sulfur dioxide pad combined with a liner is effective in reducing foodborne pathogens L. monocytogenes and S. enterica Thompson; whereas use of a slow sulfur dioxide release pad alone was more effective in controlling E. coli O157:H7.

Technical Abstract: We examined the survival of Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella enterica Thompson inoculated on commercially packed table grapes under simulated in-transit conditions (1.1ºC with 90% RH) for up to three weeks. Grapes were packed in perforated polyethylene cluster bags, within a commercial expanded polystyrene box equipped with a sulfur dioxide (SO2) generating pad and a perforated polyethylene box liner (1% vented area). L. monocytogenes was sensitive to both cold temperature and to SO2 pad. SO2 pad inactivated this pathogen completely after 12 days of incubation. E. coli O157:H7 had the highest tolerance to cold temperature and to SO2 pad; SO2 pad inactivated this pathogen completely after 20 days of incubation. S. enterica Thompson displayed similar survival fitness as L. monocytogenes, but was more resistant to SO2 pad than L. monocytogenes. While SO2 pad eliminated S. enterica Thompson after 20 days of incubation, combination of liner with a SO2 pad inactivated this pathogen completely after 13 days of incubation. Our data suggest that use of slow release SO2 pad combined with liner is effective in reducing foodborne pathogens L. monocytogenes and S. enterica Thompson, while use of SO2 pad alone was more effective on E. coli O157:H7.