What is the reason why fermented rice turns sour

You may not be very familiar with fermented glutinous rice, but it is a very important part of the wine-making process. The quality of wine also mainly depends on the quality of the fermented rice. When making fermented glutinous rice, it is generally necessary to do it in a sealed environment to prevent the fermented glutinous rice from being infected by bacteria and causing it to deteriorate. Many people find that fermented rice turns sour, but they don’t know why. So, what is the reason why fermented rice becomes sour?

What causes wine to become sour?

1. In the process of making sweet wine, it is an open operation. In such an operating environment, it is inevitable to come into contact with many other bacteria, the main one of which is lactobacillus. Lactic acid bacteria are anaerobic bacteria that use sugars to produce lactic acid. The growth of lactobacilli and yeasts showed antagonism. When lactobacillus grows in large quantities and produces lactic acid, the pH value of the mash decreases, causing the yeast to coagulate and denature, and eventually leading to the death of the yeast.

2. Acetic acid bacteria is also a major source of pollution. Oxidizes alcohol to acetic acid.

3. In addition to the above infection caused by careless operation, there is also the problem of not steaming the rice thoroughly, resulting in a low degree of starch gelatinization, which is not conducive to the growth of Rhizopus and affects the saccharification step. The direct consequence is that the fermented glutinous rice is not sweet. At the same time, certain bacteria that can directly decompose starch may also grow.

4. Of course, there are many factors that cause sourness, such as the quality of the koji, adding the koji before the rice has cooled, and the fermentation temperature... However, they are all the result of the activities of the above-mentioned "workers".

Can you still eat sour fermented rice?

The sourness of glutinous rice wine is usually caused by the reproduction of some putrefactive bacteria (such as lactic acid bacteria), which eventually produce organic acids such as lactic acid, acetic acid or citric acid in the wine. Theoretically, as long as these acids exist, no matter if they are diluted, sugar is added, or even re-fermented with new wine, it cannot make it completely sweet, but can only reduce the sour taste. If you want to continue eating it, you can add some sugar after it is completely boiled and it can still be eaten. These acids are not harmful to the human body (if it is left at room temperature for a long time and becomes sour, it cannot be eaten).

What does wine taste like?

Sweet wine tastes sweet with a slight wine flavor, is mellow and sweet, rich in nutrition, easy to digest and absorb, good for health, and is suitable for consumption by people of all ages. But you have to be prepared for failure when making fermented glutinous rice. Practice a few times, and know which containers to use, where to ferment at home (in the kitchen or next to the heater), and how to keep it warm. Once you have formed a series of production rules, it will be easy.

Key points for making fermented glutinous rice

1. Make sure to mix the koji after the glutinous rice has cooled completely. Otherwise, the hot glutinous rice will kill the gray mold. The result is either sour and smelly, or nothing happens.

2. Make sure it is tightly closed. Otherwise it will be sour and astringent.

3. Low temperature is not acceptable. Around 30℃ is best.