| Summary: | The anti-yeast activity of oil-in-water encapsulated nanoemulsion containing individual or a combination of the three essential oils of Tasmanian pepper leaf (<i>Tasmannia lanceolata</i>), lemon myrtle (<i>Backhousia citriodora</i>), and anise myrtle (<i>Syzygium anisatum</i>) against weak-acid resistant <i>Zygosaccharomyces bailii</i> in clear apple juice was investigated. The effectiveness of the shelf-life extension of <i>Z. bailii</i>-spiked (1 × 10<sup>3</sup> CFU/mL) clear apple juice was evaluated and compared between natural (essential oils) and synthetic (sodium benzoate) antimicrobial agents. Essential oils showed an immediate reduction in the <i>Z. bailii</i> cell population at day-0 and exerted a fungicidal activity at day-4 of storage, with no further noticeable growth at the end of the experiment (day-28). At lower concentrations, Tasmanian pepper leaf oil of 0.0025% had >6 log CFU/mL at day-12 of storage. For lemon myrtle essential oils, the yeast population reached >6 log CFU/mL at day-24 and day-20 for concentrations of 0.02% and 0.01%, respectively. The fungicidal activity of Tasmanian pepper leaf oil reduced from 0.005% to 0.0025% <i>v</i>/<i>v</i> when mixed at a ratio of 1:1 with anise myrtle oil. The results of the present study suggest that these three native Australian herbs have the potential to be used in the beverage industry by controlling <i>Zygosaccharomyces bailii</i> in clear apple juice products.
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