Wine production from IR50404 rice and purple sweet potato (Ipomoea batatas) using glucoamylase and Saccharomyces cerevisiae

This study develops a process for producing non-distilled wine from Japanese purple sweet potato and IR50404 rice using glucoamylase for starch saccharification and Saccharomyces cerevisiae for ethanol fermentation. Saccharification experiments examined three rice-to-sweet-potato ratios and three enzyme levels, while fermentation experiments evaluated three yeast levels and three primary fermentation durations. A 1:3 rice-to-purple-sweet-potato ratio with 1% glucoamylase at pH 4.2 for one hour produced the highest reducing sugar concentration, 6.47 mg/mL. The saccharified wort was adjusted to approximately 25°Brix, inoculated with 0.5% S. cerevisiae, and fermented at 30°C for six days, yielding 11.01% v/v alcohol. After 90 days of secondary fermentation, ethanol reached 11.7% v/v. The wine was pink-red, contained no detectable water-soluble synthetic colorants, and met applicable limits for methanol and aldehydes.