Zygosaccharomyces bailii and Z. rouxii induced ethanol formation in apple juice supplemented with different natural preservatives: A response surface methodology approach.

In this study, ethanol produced by osmophilic yeasts, Zygosaccharomyces bailii and Z. rouxii, in apple juice preserved with mint essential oil (MEO), carvacrol and natamycin instead of synthetic preservatives was modeled. Some processing parameters such as sodium benzoate (SB, 0-0.1%) used as a positive control, storage temperature (4-20 °C) and storage time (1-41 days) were selected in the study. Box-Behnken design in response surface methodology was used to evaluate the effects of processing parameters on ethanol levels of apple juice and three models were created for three preservatives for each yeast. Preservative type affected the ethanol formation in apple juice for both yeasts studied. Increase of preservative concentration decreased the ethanol formation during the storage period. The best effective preservative was determined as MEO and Z. bailii was found to be quite resistant yeast against to the preserving agents for three models as compared to Z. rouxii. Ethanol level increased with the increase of both storage temperature and time for both yeasts. The results showed that apple juice could be preserved by these three preservatives, but the MEO was the most effective agent for apple juice during the storage.