Rapid evaluation of ergosterol to detect yeast contamination in fruit juices

Foods and beverages are nutrient-rich systems prone to a rapid development of microorganisms that hamper their long-period storage. Particularly, yeasts are strong fermenters of fresh and processed fruits and vegetables; hence, they are often accountable for their spoilage and production of off-flavor. This work provides a quick and easy tool to recognize and count the spoilage of juices with ergosterol as distinctive biomarker of molds and yeasts. Melon juice was reconstituted at natural physical-chemical parameters according to legislation, and Saccharomyces cerevisiae was selected as yeast to contaminate the juice. Chemical and enzyme tests were performed on the fresh juice to ensure its authentic properties. Ergosterol was then evaluated using a spectrophotometric method that was proven against the official plate count test. The study showed linear and consistent results and, therefore, the ergosterol molecule may be indicated for testing molds and yeasts in contaminated beverages, replacing the common and time-consuming analysis.