Comparison of the antimicrobial activities of roselle calyx extracts and chemical sanitizers directly onto contaminated cucumbers

Cucumbers are associated with foodborne disease caused by Salmonella. Fruits and vegetables in restaurants and homes in Mexico are disinfected using sodium hypochlorite and colloidal silver solution. However, a number of studies show that chemical agents used to eliminate pathogenic bacteria have a limited antimicrobial effect. Previous studies show that roselle calyx extracts have antimicrobial effects. Therefore, the present study examined the attachment of 14 foodborne bacteria to whole cucumber in the presence of Hibiscus sabdariffa calyx extracts, sodium hypochlorite, acetic acid, and colloidal silver. Cucumbers were inoculated with 14 bacteria: Listeria monocytogenes, Shigella flexneri, Staphylococcus aureus, Salmonella Typhimurium, Salmonella Typhi, Salmonella Montevideo, Salmonella Choleraesuis, Escherichia coli O157:H7, non-O157:H7-Shiga toxin-producing E. coli, enteropathogenic E. coli, enterotoxigenic E. coli, enteroinvasive E. coli, enteroaggregative E. coli, and Vibrio cholerae O1. The antibacterial effect of four roselle calyx extracts (in water, methanol, acetone, and ethyl acetate) and some chemical sanitisers including sodium hypochlorite, colloidal silver, and acetic acid were then examined. All foodborne bacteria successfully attached to cucumber. The acetonic and methanolic roselle extracts caused a greater reduction (up to 4 log cfu in some cases) in the concentration of all foodborne bacteria than sodium hypochlorite, colloidal silver, and acetic acid. Thus, roselle calyx extracts may be a potentially useful disinfectant for cucumbers in the field, in processing plants, and in restaurants and homes.