Production of vinegar may vary from traditional methods employing wood barrels (Orleans Process) and generator fermentation to submerged fermentation in acetators (Fringes process)
Orleans Process
The earliest vinegar manufacturing method, which was originated in France, was known as the ‘Orleans process’ or also known as the ‘slow process’.
Wooden barrels are used and are filled with alcohol fermenting liquid to almost three quarters full. Holes are drilled into the ends of the barrel a few inches above the liquid level in order to allow air circulation. The holes are left open and netting or screens are placed over the holes in order to prevent insects from getting into the barrels. Fresh vinegar is added to the barrel to acidify the liquid to the point of optimum growth necessary for the vinegar bacteria. The vinegar bacteria settle down into the liquid and a slimy layer develops on the top of the liquid.
Generator fermentation
As a result of the Orleans process being so slow and time consuming, other methods have been adapted in order to try and speed up the process. The German method is one such way, known as the ‘generator process’ or also known as the ‘quick process’.
Orleans Process
The earliest vinegar manufacturing method, which was originated in France, was known as the ‘Orleans process’ or also known as the ‘slow process’.
This is a slow process because the bacteria come in contact with the air and the substrate only at the surface. The air is supplied through the holes in the barrel. The fermented liquid is allowed to sit for several months with free access to air. Once the alcohol fermenting liquid becomes acetified or is converted to vinegar through activity of organisms growing on or close to the surface of the liquid, a proportion of the vinegar may then be drawn off and replaced with alcohol fermenting liquid and the process is restarted. The acetic acid may become oxidised if the alcohol sources are not constantly added to the vinegar.
Today, only a very small proportion of the world’s vinegar is produced by this Orleans method, although it is reported to be the best method to produce the finest quality vinegars.
Generator fermentation
As a result of the Orleans process being so slow and time consuming, other methods have been adapted in order to try and speed up the process. The German method is one such way, known as the ‘generator process’ or also known as the ‘quick process’.
In this process the alcoholic solution to be acetified is allowed to trickle down through a tall tank or column packed with porous solid material on whose surface Acetobacter bacteria are permitted to grow. Suitable solids, which are frequently used, are wood shavings or corncobs. This column in the vinegar industry is known as a generator.
The bacteria grow upon the surface of the wood shavings and form a thick slime coating around the non-compacting material such as beech wood shavings. The air enters the generator at the bottom and moves upwards towards the top. The acetic acid bacteria use the air in order to oxidise the alcohol. A limited air supply means limited acetic acid production while an overabundant air supply creates over production and higher generator temperatures.
In order to achieve efficient vinegar production it is necessary to provide an ample supply of oxygen to the liquid substrate without passing air though the substrate at a rate which will cause excessive losses of alcohol or acetic acid by evaporation. The generator needs to be carefully monitored to present over oxidation or unacceptable high temperatures in order to avoid damaging the bacteria.
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