| Summary: | In this study, the effects of carvacrol addition which is a natural preservative to apple juice samples contaminated with Z. bailii which is an osmotolerant yeast and shows resistance against high sugar concentration, low acidity, ethanol content and pasteurization process, were investigated on some physicochemical and bioactive properties and also changes in yeast numbers during storage period. For this purpose, the response surface methodology was applied and storage time (1-41 days), storage temperature (4-20°C), sodium benzoate amount (0-0.1%) and carvacrol amount (0-750 ppm) were selected as processing variables. Significant changes in physicochemical properties were observed due to yeast viability occurred during the storage of apple juice samples. The increase in the amount of carvacrol caused a decrease in the number of yeasts about 7 log level and prevented the spoilage of fruit juices. However, the brix value of the samples without carvacrol showed a decrease of 50% as a result of yeast activity and the fruit juice could not be consumed. Total phenolic content of the sample was in the range of 136.7-645.7 mg GAE/L and the lowest total phenolic content was determined for the run 11 having no carvacrol while the highest total phenolic content was for the sample added with the highest carvacrol level. As a result of the optimization process, it was observed that the deterioration activities of Z. bailii could be prevented to a great extent by the addition of maximum amount of carvacrol.
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