Effects of the fruit maturity, processing method, and fermentation time on the physicochemical, functional, and microbial properties of Prunus mume (maesil) sugar syrup during a 1-year fermentation period

Abstract

This study focused on the effects of maturity, ripening, and fermentation time of the Prunus mume fruit (maesil in Korean) on the physicochemical, functional, and microbial properties of maesil sugar syrup during a 1-year fermentation period. All syrup samples exhibited pH values of 2.28–2.89 throughout the study. Soluble solid, moisture, and ash contents were 48.37–57.67 °Brix, 3.87–8.22%, and 0.25–2.22%, respectively. The pH values and moisture content did not fluctuate widely. The soluble solid content was nearly constant; in contrast, ash content, color values, total phenolic and flavonoid contents, and antioxidant potential increased with fermentation time. Results of microbial profiling revealed the absence of Escherichia coli and other bacteria in all sugar syrups. In contrast, yeast was detected in all samples, and the yeast count increased as fermentation proceeded. The most prominent change in yeast count, from 3.66 log CFU/mL to 5.41 log CFU/mL, was detected in unripe whole-maesil syrup. Aged whole-maesil syrup from unripe fruits also exhibited the highest antioxidant potential and total phenol (416.12 ± 8.04 μg/mL GAE) and flavonoid (140.49 ± 1.45 μg/mL QE) contents. These findings indicate that aged whole-maesil syrup from unripe fruits had desirable functional properties, which improved with fermentation time.