Combination of ultrasound and antimicrobial compounds towards Pichia spp. and Wickerhamomyces anomalus in pineapple juice

- Power affected yeasts viability more than the duration of pulse or of the time.
- US reduced the initial cell count; antimicrobials controlled the growth.
- The effect of antimicrobials was not univocal.

This research addresses the use of ultrasound (US) as a tool to inhibit Wickerhamomyces anomalus, Pichia guilliermondii and Pichia membranifaciens: they were initially inoculated in distilled water and US-treated by modulating power (40-80%), duration of the treatment (2-6 min) and pulse (2-6 s). Thereafter, yeasts were inoculated in a lab medium, containing a commercial citrus extract and/or sodium benzoate, and US-treated; finally, a challenge test in pineapple juice was performed, using W. anomalus as a model yeast. The results showed that power was the most significant parameter for the anti-yeast effect of US; however, the treatment could not prevent the growth of survivors within storage, thus the use of antimicrobials is advisable as an additional tool to prevent yeast spoilage.