Characterization of Red Dragon Fruit Wine Fermented with a Newly Identified Yeast Strain Saccharomyces cerevisiae M7.

Research background: Dragon fruit (Hylocereus spp.) has been known to be a rich source of bioactive compounds, such as anthocyanins, betacyanin, betaxanthin and other phenolic substances, and it has a nutritional profile suitable to produce wine with functional properties. The aim of this study is to characterize the wine fermentation from red dragon fruit juice by a newly identified yeast strain.

Experimental approach: Yeast strains from banh men, a Vietnamese traditional alcoholic fermentation starter, were screened for ethanol production using thermally pretreated red dragon fruit juice. The most potent candidate was identified by the DNA sequencing method and subjected to an optimization study using a one-factor-at-a-time approach to optimize the conditions for red dragon fruit wine fermentation.

Results and conclusions: Results showed that thermal pretreatment of the red dragon fruit juice at 70 °C for 10 min resulted in a higher amount of phenols and antioxidants than at other pretreatment temperatures. Among the four isolates, M7 was the strongest alcohol fermenter, which was then identified as Saccharomyces cerevisiae using a DNA sequencing method. The optimal conditions for wine fermentation from red dragon fruit juice by S. cerevisiae M7 included a pitching rate of 10⁸ CFU/mL, an initial sucrose content of 18 % (m/V), an initial pH=4.5, fermentation temperature of 30 °C and a fermentation time of 6 days. Under these conditions, the wine fermented by S. cerevisiae M7 had an ethanol volume fraction of (12.1±0.2) %, the concentration of total phenolics expressed as gallic acid equivalents (37.8±0.4), anthocyanins expressed as cyanidin 3-glucoside equivalents (11.2±0.3), betacyanin (65.2±0.8) and betaxanthin (60.5±1.3) mg/L and antioxidant activity measured by DPPH scavenging capacity of (65.4±0.4) %.

Novelty and scientific contribution: This study used a novel yeast strain Saccharomyces cerevisiae M7 for fermentation. In addition, the results of the study provide new data such as the optimal parameters and the accumulation of bioactive compounds (phenols, anthocyanins and betalains) related to the fermentation of red dragon fruit wine.