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

Thomas-Popo, Emalie, Mendonca, Aubrey, Dickson, James, Shaw, Angela, Coleman, Shannon, Daraba, Aura, Jackson-Davis, Armitra, Woods, Floyd
Food control 2019 v.106 pp. 106727
Escherichia coli O157, Listeria monocytogenes, Salmonella enterica, Yucca schidigera, agar, minimum inhibitory concentration, pathogens, pineapple juice, refrigeration, sensory properties
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 < 0.05). Within 24 h, all isoeugenol treatments achieved >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.