Study of fermentation process of rice wine prepard using local raw materials

Abstract

Rice wine is alcoholic beverage made by simultaneous saccharification and fermentation by using mold and yeast respectively. In Nepal, traditional starter culture locally known as murcha has been used for fermentating locally available raw materials such as millet, rice, wheat, etc. The quality of alcoholic beverage always varies due to lack of process standardization in term of culture and process. Here, an attempt was made to isolate and screen mold and yeast from the murcha collected from different districts of Nepal and used in production of rice wine. The performance of mold was tested for saccharifying capacity and yeast for sugar, alcohol, pH tolerances and alcohol production. Most potent yeast isolates were identified by molecular tool using 18s universal primer. Seven molds isolates from murcha were tested for saccharification by halo zone on starch media, microscopic observation, liquefication and DNS test. All yeast isolates were also compared with commercial yeast (Saccharomyces Bayanus SN9). The results showed that all yeast isolates reproduced by budding, used glucose and sucrose as carbohydrate source during fermentation except murcha from Ramechhap district. Murcha used glucose and sucrose and none of them used starch, all isolates showed positive result of urea hydrolysis test except murcha from Parbat and commercial yeast. All isolates exhibiting growth in yeast-peptone-dextrose broth containing 40% glucose, 15% alcohol and pH ranges from 3-5.5. Alcohol production test measured by hand refractometer in YPD broth showed that isolates changed ˚Brix from 20 to 4.5 within 2 weeks at 28˚C. Among eight isolates, murcha from Parbat sample showed better performance in term of alcohol production. Yeasts isolates from Parbat and Dolakha district murcha showed 99% identity with Saccharomyces boulardii and Saccharomyces cerevisiae respectively during BLAST. All mold isolates showed better growth in Peptone, Beef extract, Starch and Agar (PBSA) media. All mold isolates produced fermentable sugar in ranges of 299.16µg/ml to 417.08 µg/ml. Yeast and mold from Parbat district was used for fermentation of rice wine. During fermentation change in acidity, ˚Brix and pH respectively 1.0-2.6 g/L, 1-5 and 4.13.4. After pasteurized rice wine showed 5% abv, 1.5 g/L succinic acid, 0.27 g/Laminoacid, 5.8 ˚Brix, 4.7 pH, 0.56 g/100 mL glucose and not detected methanol (g/100 L).

Key words: Murcha, saccharification, fermentation, tolerance tests, rice wine