Abstract: The preparation of water extract from roselle grown in Yunnan and the fermentation of roselle wine were optimized using one-factor-at-a-time method and response surface methodology. Results showed that a solid-to-solvent ratio of 1:28 (g/mL), an extraction temperature of 84.0 ℃ and 78 min extraction were found to be the optimal conditions to obtain a higher yield of anthocyanins and polyphenols of (0.060 ± 0.009)% and (0.201 ± 0.05)%, respectively. The optimal fermentation conditions were as follows: temperature 24.5 ℃, yeast inoculum size 1.6 g/L, and sugar 22.5%. The wine produced under these conditions contained (10.6 ± 0.12)% alcohol (V/V), (121.25 ± 0.35) mg/L anthocyanins, and (629.58 ± 0.22) mg/L polyphenols. It also contained a variety of amino acids with a balanced amino acid composition. Seven organic acids and eight phenolic acids were identified in the water extract, with citric acid, hibiscus acid and protocatechuic acid being the major constituents. However, hibiscus acid and lactic acid were the main organic acid and protocatechuic acid was similarly the main phenolic acid in the wine. During fermentation, the contents of citric, hydroxycitric and tartaric acid decreased while the opposite was observed for pyruvic, lactic and succinic acid. In addition, an decrease in protocatechuic, gentisic and ferulic acid was observed, accompanied by an increase in gallic, coumaric and syringic acid.

Key words: roselle, anthocyanins, polyphenols, organic acids, phenolic acids, response surface methodology