Sodium benzoate and sodium bisulfate as preservatives in apple juice and alternative sanitizers for washing cherry tomatoes

Unpasteurized apple ciders and fresh produce have been linked to multistate outbreaks due to contamination by foodborne pathogens. Organic acids such as benzoic acid are effective antimicrobials, and acidified sodium benzoate (NaB) has been reported to be effective in reducing pathogens inoculated on cherry tomatoes and preventing cross-contamination. Sodium bisulfate (SBS) is a powerful acidulant but has not been studied in combination with NaB. The objective of the present study was to characterize the antibacterial activity of SBS and its combination with NaB in tryptic soy broth (TSB) and apple juice, as well as washing cherry tomatoes. The minimum inhibitory concentration and minimum bactericidal concentration of SBS were all 0.5% w/v (corresponding to TSB medium pH of 4.30) and 1.0% w/v (corresponding to TSB medium pH of 2.88), respectively, for Escherichia coli O157:H7 ATCC 43895, Salmonella Enteritidis ATCC 13076, and Listeria monocytogenes Scott A. In TSB, the triple combination of 1.0% w/v SBS, 0.1% w/v NaB, and 0.02% w/v oregano oil (OO) showed the faster inactivation rate of the three bacteria than treatments with one or two antimicrobials; the activity of double combinations followed the order of 0.1% w/v NaB +1.0% w/v SBS > 0.1% w/v NaB +0.5% w/v SBS + 0.02% w/v OO > 0.1% w/v NaB +0.5% w/v SBS. pH was a critical factor in the activity of antimicrobial combinations in TSB, and L. monocytogenes was more resistant than Gram-negative E. coli O157:H7 and S. Enteritis. In apple juice added with 0.05% w/v NaB, 0.25% w/v SBS, and 0.01% w/v OO alone or in combinations, 5 log CFU/mL or greater reductions in 72 h were observed for E. coli O157:H7 and S. Enteritidis in double and triple combinations, while only the triple combination and the SBS-OO combination resulted in the same effect for L. monocytogenes. For cherry tomatoes inoculated with 6.8 log CFU/g E. coli O157:H7, complete decontamination (>6 log CFU/g) was achieved after soaking for 1 min in solutions containing 0.5–1.5% w/v SBS and 0.1% w/v NaB or 1.5% w/v SBS alone, and no pathogens were detected in all wash solutions containing 0.5–1.5% w/v SBS with and without NaB. The lower pH of wash solutions with a higher amount of SBS was a dominant factor in decontamination and prevention of cross-contamination. The present study showed the potential of SBS and its combination with NaB to enhance the safety of apple juice and cherry tomatoes.