Bactericidal effects of roselle (Hibiscus sabdariffa) against foodborne pathogens in vitro and on romaine lettuce and alfalfa sprouts

Introduction An increased fresh-produce consumption trend accompanied by increased associated outbreaks suggests a need for better intervention strategies. Limitations of chemical sanitizers have necessitated alternative strategies. Research on antimicrobial properties of roselle against food pathogens is limited. Objectives The study aims to investigate Escherichia coli O157:H7, Salmonella enterica and Listeria monocytogenes survival in roselle calyx aqueous (RCA) or roselle leaf aqueous (RLA) extracts over 72 h at 4, 8 and 25 degrees C; bactericidal effects of roselle calyx concentrate (RCC) and roselle tea (RT) against E. coli O157:H7 on lettuce and of RCC against Salmonella on alfalfa sprouts. Methods Microbiological analyses and preparation of RCA, RLA, RCC and RT were done according to standard and established methods. Results No E. coli O157:H7 and Salmonella survivors were detected in RCA or RLA at 24 h and all temperatures. L. monocytogenes population was reduced by 5 and 3 logs in RCA and RLA, respectively, at 24 h and all temperatures; by 4-6 logs at 4 degrees C and 8 degrees C and to undetectable levels at 25 degrees C, at 48 h. At 24 h, E. coli O157:H7 and Salmonella were not detected on RCC- or RT-treated lettuce or sprouts. Conclusion These observations suggest the application of roselle extracts as potential antimicrobials in foods.