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United States Department of Agriculture

Agricultural Research Service

Title: Localization, growth, and inactivation of Salmonella Saintpaul on jalapeno peppers

item Liao, Ching Hsing
item Cooke, Peter
item Niemira, Brendan

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2010
Publication Date: 9/18/2010
Citation: Liao, C., Cooke, P.H., Niemira, B.A. 2010. Localization, growth, and inactivation of Salmonella Saintpaul on jalapeno peppers. Journal of Food Science. 75(6):M377-M382.

Interpretive Summary: In 2008, one of the largest foodborne illness outbreaks due to the consumption of raw jalapeño peppers was reported in at least 40 states and sickened more than 1,400 people in the U.S. A disease-causing bacterium (named Salmonella Saintpaul) present on tainted jalapeño peppers has been identified as the culprit behind this outbreak. This study was conducted to investigate the localization, growth potential, and means for inactivation of Salmonella Saintpaul on jalapeño peppers. Data presented showed that more than 90 percent of Salmonella Saintpaul was detected in the stem and calyx portion of an intact fruit and only a small proportion was detected on fleshy pod. A rapid multiplication of Salmonella Saintpaul was observed on peppers that were stored at room temperature (approximately 20 deg C). A long-term survival of Salmonella Saintpaul for at least 8 weeks, but no sign of growth, was detected on peppers that were stored at 4 deg C. Soaking contaminated peppers in one of three sanitizer solutions (chlorine, acidified sodium chlorite, and peroxyacetic acid) for 10 minutes can remove 90 to 99 percent of Salmonella Saintpaul from contaminated peppers. Post-harvest storage at refrigeration temperature and sanitizer treatment can greatly reduce the risk of tainted jalapeño peppers serving as a vehicle for transmission of foodborne illness.

Technical Abstract: Consumption of Salmonella-contaminated jalapeño peppers has been implicated in one of the largest foodborne illness outbreaks in the summer of 2008. The objective of this study was to investigate representative groups of native microflora and the distribution, growth, and inactivation of experimentally-inoculated Salmonella Saintpaul on jalapeño peppers. Two genetically-modified strains of Salm. Saintpaul producing either green- or red-fluorescent protein were constructed and used in the study. Microbiological analyses showed that jalapeño peppers contained an average of 5.6 log units of total aerobic count and 3.5, 1.8, and 1.9 log units, respectively, of enterobacteriaceae, lactic acid bacteria, and yeast/mold per gram of tissue. Strains typical of Pseudomonas accounted for 8.3% of total aerobic count, and 0.2 % of which exhibited pectolytic activity. On inoculated peppers, a vast majority (> 90%) of Salm. Saintpaul was recovered from stem/calyx and only a small proportion recovered from fleshy pods. Growth of Salm. Saintpaul on peppers was indicated by an increase in the population of 3 log units after incubation of samples at 20 C for 48 hr. Fluorescent Salm. Saintpaul aggregates could be readily detected on stem/calyx using stereofluorescence imaging microscopy and scanning electron microscopy. Data presented showed that Salm. Saintpaul could survive for at least 8 weeks on peppers stored at 4 C. Immersion of inoculated peppers in 200 ppm of sodium hypochlorite, acidified sodium chlorite, or peroxy acetic acid for 10 min could reduce the number of Salm. Saintpaul on stem/calyx by 1.5 to 1.7 and that on flesh by 2.1 to 2.4 log units.

Last Modified: 10/18/2017
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