Question

Soy sauce is prepared by fermenting a salted mixture of soybeans and wheat with several microorganisms including yeast, over a period of 8-10 months. After the solids are removed, the resulting sauce is rich in lactic acid and ethanol. How are these two compounds produced (show mechanism). To prevent the soy sauce from having a strong vinegar taste, oxygen must be kept out of the fermentation tank, why?

Answer 1

If the fermentation tank is contaminated with oxygen ; then the produced ethanol will further be oxidised to acetic acid which is major compnent of vinegar and the soya sauce will have the taste of vinegar.

So, to prevent the oxidation of alcohol to acid; oxygen should be kept out from tank.