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 72h at 4, 8 and 25°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 24h and all temperatures. L.monocytogenes population was reduced by 5 and 3 logs in RCA and RLA, respectively, at 24h and all temperatures; by 4-6 logs at 4°C and 8°C and to undetectable levels at 25°C, at 48h. At 24h, 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.