A method for automatically controlling the feed rate of alcohol solution as raw material in a process for producing vinegar by acetic acid fermentation, utilizing an automatic alcohol analyzer for measurement of alcohol concentraction in a fermenting broth, a feeding apparatus for feeding alcohol solution as raw materials to said fermenting broth, and a control computer controllably coupled to said alcohol analyzer and to said feeding apparatus, the method comprising:
- periodically measuring the alcohol concentration in said fermenting broth by said automatic alcohol analyzer by a direction from said control computer at given intervals over a plurality of cycles of measurement;
- calculating in said control computer a feed rate of alcohol solution as raw material to said fermenting broth so as to control the alcohol concentration in said fermenting broth at at a desirable concentration on the basis of a difference between a measured alcohol concentration in said fermenting broth and a desirable alcohol concentration and the alcohol consumption rate calculated during each of said cycles by said control computer;
- and then
- controlling operation of said feeding apparatus to control the feed rate of said alcohol solution responsive to a control signal generated by said control computer as a result of said calculations, which control signal is coupled to said feeding apparatus for feeding alcohol solution as raw material to said fermenting broth.