Preparation of edible acetic acid

The preparation of acetic acid can be achieved by two methods: artificial synthesis and bacterial fermentation. Biosynthesis, that is, the use of bacterial fermentation, accounts for only 10% of the entire world production, but is still the most important method for the production of acetic acid, especially vinegar, because the food safety regulations of many countries stipulate that vinegar in food must be produced by biological methods. The fermentation method is divided into aerobic fermentation method and anaerobic fermentation method.

aerobic fermentation

In the presence of sufficient oxygen, Acetobacter bacteria are able to produce acetic acid from foods containing alcohol. Usually cider or wine is mixed with grain, malt, rice or potato and then fermented. These substances can be fermented to acetic acid under the action of catalytic enzymes in the presence of oxygen.

The specific method is to inoculate the bacteria of the genus Acetobacter in the diluted alcohol solution and keep it at a certain temperature, and place it in a ventilated place. It can be fermented within a few months and finally produce vinegar. The method of industrial production of vinegar speeds up the reaction process by providing sufficient oxygen. This method has been adopted in commercial production. It is also known as the "rapid method" or "German method", so it is named after the first successful application in Germany in 1823. . In this method, fermentation takes place in a tower filled with sawdust or charcoal. The raw material containing alcohol drips in from the top of the tower, and fresh air enters naturally or forced convection from below. The enhanced air volume enables this process to be completed in a few weeks, greatly reducing the time required to make vinegar.

Otto Hromatka and Heinrich Ebner first proposed the preparation of vinegar from a liquid bacterial culture medium in 1949. In this method, the alcohol is fermented to acetic acid under constant stirring, and air is charged into the solution in the form of bubbles. By this method, vinegar containing 15% acetic acid can be prepared in two to three days.

Anaerobic fermentation

Some anaerobic bacteria, including some members of the genus Clostridium, are able to convert sugars directly to acetic acid without the need for ethanol as an intermediate. Sucrose can be fermented to acetic acid in an anaerobic environment.In addition, many bacteria are capable of producing acetic acid from compounds containing only one carbon, such as methanol, carbon monoxide or a mixture of carbon dioxide and hydrogen.