Isoeugenol significantly inactivates Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes in refrigerated tyndallized pineapple juice with added Yucca schidigera extract

Abstract The antimicrobial effectiveness of isoeugenol against Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes in refrigerated (4 °C) pineapple juice (PJ) with added 0.5% (w/v) yucca extract (YEX) was investigated. Sub-lethal injury of pathogen survivors and sensory characteristics of PJ were also evaluated. Samples of PJ with YEX and isoeugenol at 0 (control), 0.50, 0.75, 1.0, or 1.5 μL mL −1 were each inoculated with a five-strain mixture of one pathogen to obtain an initial viable count of ∼7.1 log CFU mL −1 . During storage of PJ at 4 °C for 70 days, numbers of non-injured and sub-lethally injured survivors were determined by plating diluted juice samples on selective and non-selective agar. The minimum inhibitory concentration (MIC) of isoeugenol for E. coli O157:H7 and S. enterica was 0.5 μL mL −1 in brain heart infusion broth and the MIC for L. monocytogenes was 0.2 μL mL −1 . The minimum bactericidal concentration (MBC) for E. coli O157:H7 and S. enterica was 0.6 μL mL −1 while the MBC for L. monocytogenes was 0.4 μL mL −1 . All three pathogens survived for more than 42 days in the control juice. After 2 h, isoeugenol inflicted sub-lethal injury in pathogen survivors. Isoeugenol at 1.5 μL mL −1 completely inactivated E. coli O157:H7 and S. enterica after 4 h and 6 h, respectively (P  5 log reduction of each pathogen. However, the PJ samples with isoeugenol at 0.5 μL mL −1 were the only ones acceptable for all sensory attributes evaluated. Isoeugenol (0.5 μL mL −1 )/YEX combination has good potential for enhancing the microbial safety of refrigerated PJ without negatively affecting sensory attributes of the juice.