Why does the brewing process turn sour? What are the chemical reactions?

In the brewing process, if the alcohol in yellow rice wine reacts with oxygen in the air, it will be converted into acetic acid and water, so it will turn sour, that is, ethanol will be converted into acetic acid.

Chemical reaction equation: C2H5OH+O2==CH3COOH+H2O.

[Brewing technology]: C6H 12O6 (enzyme) →2C2H5OH (alcohol) +2CO2+ a little energy.

Generally, when brewing wine, plant fruits rich in starch, such as rice, corn, sorghum, etc. , cooking, then adding a small amount of cold boiled water into distiller's yeast (containing glucoamylase and alcoholase) to make turbid liquid, and then mixing it with cooked food evenly. When placed at 30 ~ 40℃, the reaction is as follows:

(C6H 10O5)n (starch) +nH2O → nC6H 12O6 (glucose)? At this time, in order to verify whether glucose is generated, if red precipitate is generated, a small amount of product can be taken out and mixed with newly generated copper oxide for heating. Prove that glucose has been obtained. If you want to know whether starch is completely converted into glucose, you can take a small amount of iodine and add it to it without turning blue. The first step is completed. After glucose is produced, glucose is oxidized into ethanol under the action of alcoholase, and the reaction is as follows:

C6H 12O6 → 2CO2 + 2CH3CH2OH？ To verify whether ethanol (alcohol) is produced, take out some solutions and insert a heated copper wire. If there is a pungent smell, it can indicate that ethanol (wine) is produced.

The reaction takes place as follows:

2CH3CH2OH + O2 → 2CH3CHO + 2H2O