Acetic acid fermentation (production of vinegar)

Lab.5.
Practical Industrial Microbiology
Acetic acid fermentation (production of vinegar)
Vinegar is essentially a dilute solution of acetic acid, made by fermentation processes,
containing salts and extracted matter.
The exact nature and quantity of these additional substances depend upon the material used;
give the product its distinctive quality.
The starting materials for vinegar may be fruits (grapes, oranges, apples, and pears), vegetables
(potatoes), malted cereals (barley, rye, wheat, corn) and sugary syrups (molasses, honey, maple
syrups).
Vinegar production involves an initial anaerobic fermentation to convert carbohydrates by
Saccharomyces cerevisiae to alcohol (ethanol),
Followed by a secondary oxidative transformation of the alcohol to form acetic acid
(acetification) by Acetobacter and Gluconobacter.
Microorganisms involved in the production of vinegar:
The organisms involved in vinegar production usually grow at the top of the substrate, forming
a jelly like mass.
This mass is known as mother of vinegar.
The mother of vinegar is composed of both Acetobacter and yeasts, which work together.
The main yeasts are S. ellipsoideus and S. cerevisiae.

Acetic acid bacteria are strictly aerobic, G+ rods, characterized by their ability to carry out a
number of oxidations and they can tolerate high concentration of acid, including A. acetics, A.
xylinum and A. ascendens.
It is important to maintain an acidic environment to suppress the growth of undesirable
organisms and to encourage the presence of desirable acetic acid producing bacteria.
It is common practice to add 10-25% by volume of strong vinegar to the alcoholic substrate in
order to attain a desirable fermentation.
Fermentation method:
1. Quick vinegar methods (German method).
2. The Orleans process (French method; slow method).
Procedure: