How is rice wine made?

Rice wine is a kind of starch fermentation, yeast can not directly use starch to convert into alcohol, so the starch needs to go through the process of hydrolysis, saccharification process can be used by the yeast to produce alcohol, for the complex fermentation. The traditional brewing of starchy liquors in oriental societies uses molds to achieve the function of hydrolysis and saccharification, so the function and value of molds and yeasts in the manufacture of rice wine or starchy liquors are equally important. The process of making rice wine using koji is shown below.

Steaming the rice→cooling it→receiving the koji→making a hole in the center of the lower tank (for ventilation)

Leaving it for 3~4 days and adding water→fermenting it for 10~14 days→distilling it→ageing it.

Steaming and cooling: The purpose of steaming rice is twofold: one is to reduce the contamination of bacteria after steaming, and the other is to make the rice swell and become a paste after steaming, which is favorable for the use of mold.

Connecting the koji to the center of the tank: Folk use of koji contains mold and yeast two kinds of mold in the early stage of the play a major role in the growth of mold during the water (starch hydrolysis liquefaction) glycolytic enzymes. Because mold is a good gas bacteria, so proper aeration is necessary.

Add water, fermentation: Yeast cannot ferment starch directly, but it can metabolize glucose into alcohol. Adding water after about 3 or 4 days can lower the concentration of glucose and reduce the acidity. The reason is because starch liquefaction produces a large amount of glucose, resulting in favorable growth of yeast, which is a strong strain in the fermentation tank compared to mold. Lowering the acidity gives the yeast a suitable environment for growth. It is not desirable for mold to proliferate during this period. The air supply should be sealed and lowered. This is because yeast will convert sugars to carbon dioxide and alcohol in the absence of oxygen. The mold continues to hydrolyze starch to glucose and the yeast metabolizes glucose to alcohol. The whole fermentation process is continuous, and the alcohol increases dramatically during this time. Eventually the process stops because of increased acidity or because the sugar has been metabolized. This process is also due to the conversion of acid and alcohol into esters. This process also results in the conversion of acids and alcohols into esters, which have specific flavors. After the yeast proliferation, changed to an anaerobic environment, you can add sugar into, because the sugar increases, the yeast thus produce a large number of decomposition enzymes, can accelerate the rate of alcohol production. It is also possible to avoid the termination of fermentation due to the decrease of mold productivity and the reduction of sugar in the later stages.

Distillation: After the fermentation is completed, the alcohol is distilled to raise the alcohol concentration and to separate the formaldehyde in the process. This process increases the alcohol concentration and separates the formaldehyde from the alcohol in the process to avoid harming the human body.

Aging: Rice or starch contains proteins, which are broken down into amino acids and react with alcohols to form esters, as well as some fatty acids that can react with alcohol to give it a unique flavor. In addition, the types of fungus contained in the koji also metabolize acidic substances and produce different flavors. In some cases, if the fungus is not controlled, it may become a strong fungus. This leads to acidification.

Fermentation Technology

There are several important factors that contribute to the production of rice wine in large quantities and the maintenance of stable quality. The role of these elements is clearer from the famous saying in the brewing industry: "Koji is the bone of sake, grain is the flesh of sake, and water is the blood of sake.

Molds and molds are mainly molds, yeasts, and a few stray molds, which are the key to the quality of the sake, and are screened for high-quality yeasts and molds in the natural environment. However, the molds and molds used in molds are not sterilized, and the molds are grown in mold rooms where the air circulates with the outside world, so not only are there yeasts and molds in the molds and molds, but also some acid-resistant and anaerobic molds, such as esterophilus, lactobacillus and lactobacillus. Therefore, not only yeast and koji are produced, but also acid-resistant and anaerobic stray bacteria, such as esterifying bacteria and lactic acid bacteria, are mixed in during koji production. The screening and preservation of koji affects the conversion rate and odor of the final alcohol. Although it is possible to stabilize the alcohol concentration by mixing high and low concentrations of fermented alcohol, it is possible to further reduce the cost by increasing the final conversion rate. The addition of these stray bacteria can cause flavor variations when using koji to make sake, and the flavor can become good or bad? or rancidity! The whole source of bacteria includes heat- and acid-resistant bacteria that may be present in the rice, bacteria in the water, and the preservation of the koji to avoid contamination. Nowadays, we separate the two strains, starch hydrolysis and yeast fermentation, and use purification and screening techniques to select and cultivate a single strain of bacteria. This makes it possible to obtain consistent flavor quality by producing the same yeast each time.

Temperature control: When mold grows and breaks down starch, it generates heat, and when that heat is not effectively removed, it accumulates and raises the temperature of the product, ultimately killing itself and the yeast in the koji. This can lead to rancidity. If the temperature is too low, the lack of heat makes it difficult to ferment for a long period of time, and although the flavor is better, the time cost is higher. It is generally believed that the better temperature is about 38 degrees to 50 degrees.

Larger fermenters: Larger fermenters can increase batch yields, but the larger size requires the incorporation of new technologies such as agitation and aeration. The yeast will have enough oxygen during re-fermentation and will be a strong strain. However, it should not be aerated continuously. This is because anaerobic environments are good for yeasts, while aerobic bacteria such as lactic acid bacteria and molds can be effectively inhibited. Let the whole tank environment is uniform and have stable output. Therefore, the introduction of aeration and proper mixing in large-scale fermentation tanks can improve the fermentation process and reduce the chance of rancidity.

Distillation: Taiwan's aboriginal home-brewed millet wine is often consumed directly without distillation, which is harmful to the human body because of the presence of methanol and formaldehyde during the fermentation process. Distillation can separate and reduce the concentration of methanol and formaldehyde. Some people say that millet wine is easy to get a headache after drinking it. This is the reason. After distillation, you can also increase the alcohol concentration.