Steaming rice → cooling → receiving koji → drilling (ventilation) in the center of the lower cylinder → standing for 3~4 days and adding water → fermentation 10 ~ 14 days → distillation → aging.
Steam refrigeration: Generally, rice steaming has two purposes, one is to reduce the pollution of miscellaneous bacteria after steaming, and the other is to make rice grains swell into paste after cooking, which is beneficial to the utilization of mold.
Connecting koji → drilling hole in the center of the lower cylinder: There are two kinds of koji used by the people: mold and yeast. Mold plays an important role in the early stage, producing glucoamylase (starch hydrolysis and liquefaction) during the growth of mold. Because mold is aerobic, proper ventilation is necessary.
Fermentation with water: Yeast can't ferment starch directly, but it can metabolize glucose into alcohol. After about three or four days, adding water can reduce the glucose concentration and reduce the acidity. The reason is that starch produces a lot of glucose after liquefaction, which is beneficial to yeast growth and is a strong strain compared with mold in fermentor. Reducing acidity gives yeast a suitable growth environment. During this period, mold is not expected to multiply in large quantities. It should be sealed to reduce the air supply. Because yeast will turn sugar into carbon dioxide and alcohol in an anoxic environment. Mold continuously hydrolyzes starch into glucose, while yeast metabolizes glucose into alcohol. The whole fermentation process is continuous production, during which alcohol is greatly increased. Finally, it will stop because of the increase of acidity or the light metabolism of sugar. This process is also due to the conversion of acids and alcohols into esters. But it has a special fragrance. After a large number of yeasts proliferate, they are transformed into anaerobic environment, so sugar can be added. Because of the increase of sugar, yeast produces a large number of decomposing enzymes, which can accelerate the production of alcohol. It can also avoid the decline of mold productivity and fermentation termination caused by the decrease of sugar in the later stage.
Distillation: After the fermentation is completed, the alcohol can be distilled out, which can increase the alcohol concentration and separate formaldehyde in the process. Avoid hurting people.
Maturity: protein is contained in rice or starch, and protein is decomposed into amino acids which react with alcohol to produce esters, and some fatty acids can react with alcohol to produce its unique flavor. In addition, the kinds of miscellaneous bacteria contained in koji will also metabolize acidic substances and produce different flavors. What's more, if the bacteria are not controlled, they will become virulent strains. Lead to rancidity.
Fermentation technology
There are several important factors to produce rice wine in large quantities and maintain stable quality. From the famous saying in the wine-making world: "Qu is the bone of wine, grain is the meat of wine, and water is the blood of wine", the roles played by these elements are more understood.
Daqu: mainly contains mold, yeast and a small amount of miscellaneous bacteria. In order to affect the quality, high-quality yeast and koji were screened in the natural environment, but it used almost unsterilized raw materials and grew in the koji room, and the air was communicated with the outside world. Therefore, in the process of producing Daqu, besides yeast and distiller's yeast, there will also be some acid-resistant and anaerobic miscellaneous bacteria, such as esterifying bacteria and lactic acid bacteria. The screening and preservation of koji will affect the conversion rate and smell of the final alcohol. Although the alcohol concentration can be kept stable after mixing high and low concentration fermented alcohol, the cost can be further reduced if the final conversion rate can be improved. Because of the addition of these miscellaneous bacteria, using distiller's yeast to make wine will also cause flavor variation, and the flavor will get better and worse? Still rancid! The whole strain source includes heat-resistant and acid-resistant bacteria that may exist on rice, raw bacteria in water and koji preservation to avoid pollution. Now starch hydrolysis and yeast fermentation are separated, and a single strain is selected for culture through purification and screening technology. So as to make all koji consistent and obtain stable flavor quality.
Temperature control: when the mold grows and decomposes starch, it will generate heat. When the generated heat cannot be effectively eliminated, it will accumulate continuously, which will increase the temperature of the product and eventually kill itself and the yeast in the koji. It is easy to lead to rancidity. If the temperature is too low, it will be difficult to ferment for a long time because of the lack of heat source. Although the taste will be better, the time cost will increase. It is generally considered that the preferred temperature is about 38 degrees to 50 degrees.
Large-scale fermentor: Large-scale fermentor can increase batch production, but some new technologies, such as stirring and aeration, need to be added after scale-up. In the process of re-fermentation, yeast has enough oxygen and is a powerful strain. But it can't be ventilated continuously. Because anaerobic environment is beneficial to yeast, it can effectively inhibit aerobic fungi, such as lactic acid bacteria and mold. So that the environment in the whole tank body is uniform and the output is stable. Therefore, introducing ventilation and proper stirring in large fermenters can improve fermentation procedures and reduce the probability of rancidity.
Distillation: Rice wine brewed by aborigines in Taiwan Province Province is often drunk directly without distillation. During fermentation, methanol, formaldehyde and other components will be harmful to human body. The concentrations of methanol and formaldehyde can be separated and reduced by distillation. Some people say that millet wine is easy to have a headache. That's why. After distillation, the alcohol concentration can also be increased.