We know that the brewing of rice wine requires the use of sake brewing, which is also called yeast, and yeast is actually a kind of unicellular fungus, the earliest microorganisms to be used in the history of human civilization. Therefore, in the process of making rice wine, we need to have certain conditions, such as sanitary conditions, brewing time and brewing temperature. The reason why we need to control the brewing temperature is mainly related to the living environment of the yeast.

Let's take a look at the growth conditions of yeast:

1 Nutrition: yeast and other living organisms need similar nutrients, like bacteria, it has a set of intracellular and extracellular enzyme system, used to break down large molecules into small molecules that are easy to utilize for the metabolism of the cell.

2 Moisture: Like bacteria, yeast must have water to survive, but yeast needs less water than bacteria.

3 Acidity: yeast can grow in the range of pH 3.0-7.5, the optimal pH value is pH 4.5-5.0.

4 Temperature: in the temperature below the freezing point of the water or higher than 47 ℃, the yeast cells can not grow, the optimal growth temperature is usually in the range of 20 ℃ ~ 30 ℃.

5 Oxygen: yeast can grow in both aerobic and anaerobic environments, i.e., yeast is a parthenogenetic anaerobic bacteria, in the absence of oxygen, yeast breaks down sugar into alcohol and carbon dioxide. In the presence of oxygen, it breaks down sugar into carbon dioxide and water, and yeast grows faster in the presence of oxygen.

By analyzing the characteristics of yeast above, we can know that the best temperature for making rice wine is between 20 degrees Celsius and 30 degrees Celsius, not below zero, below zero the yeast does not grow and does not ferment, and above 47 degrees the yeast will die.

This is the reason why we need to steam the glutinous rice and let it cool before putting the yeast in.