The value of acetic acid bacteria

2024 Author: Isabella Gilson | [email protected]. Last modified: 2024-01-02 16:12

Many winemakers are aware of the situation when, due to air entering the vessel, a film formed on the surface of the drink. This process completely spoils the taste and properties of the wine, making it unfit for consumption, and it is provoked by bacteria of acetic acid fermentation. By themselves, such microorganisms are not dangerous and are always found in wine and beer, they begin to cause harm only when they come into contact with air.

But today even this seemingly not very good property is used for the benefit of mankind in certain industries.

What are bacteria

The most striking example of the work of acetic acid bacteria is the souring of low-alcohol wine. This phenomenon was known in antiquity, but a scientific explanation of the process was given only in the 60s of the century before last by the French microbiologist Louis Pasteur. It was he who discovered the causative agents of the appearance of a cloudy film on the surface of the wine, which causes it to turn sour, in other words, turning into vinegar.

This is characteristic of low-alcohol drinks,left in incomplete open vessels with free access of air. Upon further study, it turned out that the “vinegar fungus” discovered by the chemist is actually a whole species of various bacteria.

The ability of microorganisms

Acetic acid bacteria are actually involved in the processes not only of souring wines. They are able to oxidize alcohols such as ethyl, propyl and butyl, forming from them acetic, propionic and butyric acids, respectively. That is, any drink containing such alcohol can be spoiled due to the vital activity of bacteria. Do not be afraid only for liquids containing methyl and higher alcohols, since they form a product toxic to microorganisms when oxidized.

Process Features

The self-oxidation of alcohols under the influence of acetic acid bacteria is dehydrogenation. The whole process can be expressed in a chemical formula, where ethyl alcohol is initially taken, which is converted under the influence of oxygen into acetic acid, water and the energy released:

CH₃CH₂OH + O₂=CH ₃COOH + H_{2O + energy}

If there is too much alcohol in the medium, then the result of the process will be the formation of only acid and a minimal release of energy, which is not enough for the further life of bacteria. That is why they have to oxidize as much alcohol as possible, which brings oxidation closer to other anaerobic processes, but leaves it individual in certain characteristics.

Features

A distinctive feature of the action of acetic acid bacteria is always the formation of a film on the surface of the substrate.

The work of acetic acid bacteria and their properties depend on the variety of microorganisms and can change color, thickness, strength and other characteristics. To date, a huge number of species of these typical aerobes have already been discovered. All of them are able to multiply very quickly, especially when finished acetic acid is added to the initial liquid, which speeds up the process of obtaining vinegar in production. In life, acetic acid bacteria are found in the air, soil, any fermentation product, on the surface of berries and fruits, water, and so on.

External description

Under ideal conditions, cells are short rods and do not form spores. Depending on age, habitat and many secondary reasons, the shape and size of microorganisms can change. Unfavorable conditions provoke cells to grow and sometimes become covered with mucus. In large numbers, they form mucus accumulations.

Temperature has a special influence on the vital activity of cells. If its indicator is below 15 degrees, then reproduction will be slowed down, and outwardly the bacteria will be short and thick sticks. At an indicator of up to 34 degrees, the environment is considered ideal, and the cells feel good. With an increase, the formation of various deformities in the form is possible.

Useful properties

In addition to the fact that the vital activity of bacteriaharms winemaking, there are a number of examples of successful human use of the characteristics of microorganisms.

So, the main role of acetic acid bacteria is assigned in the production and manufacture of table vinegar from wine or diluted alcohol. This is done to this day in two ways.

The first is a slower but more thorough process called Orleans or just French. For it, it is necessary to prepare wine, previously acidified or diluted with water. Place it in prepared flat containers so that the surface of contact with air is maximum, and release particles of the previously formed film of Acetobacter orleanense into the liquid. It is yellow in color and has a strong texture to keep the liquid underneath transparent.

After the end of fermentation, part of the substrate is carefully removed from the container and replaced with the same amount of diluted wine, after which the process resumes.

The second method is faster and applicable to the oxidation of dilute alcohol. To do this, it is passed through special containers with beech shavings in order to also increase the adhesion surface with bacteria. At the same time, the containers are necessarily equipped with false bottoms with the ability to pass air through them. Thus, the alcohol sprayed with air flows settles on the chips and oxidizes, after which it is taken from the vessel from below, and a new substrate is added from above.

Besides this, cages are used for:

• urinatingapples with yeast;
• ascorbic acid production;
• cultivating kombucha;
• making kefir.

In general, parallel fermentation is observed in the production of absolutely all lactic acid products, that is, lactic and acetic acid bacteria together ensure the appearance of milk processing products in the form we are used to.

Negative properties

Despite this positive value, acetic acid bacteria also pose a danger to certain industries. So, in winemaking, microorganisms are considered pathogenic, since they are able to provoke the fermentation process, despite the fact that they are almost always found in beer and wine. To deactivate them, drinks should be carefully sealed from contact with air, because it is he who provokes the onset of fermentation. The acetic acid obtained from the souring of wine always collects at the bottom, from where it can be collected, but the taste and aroma of the remaining drink will be forever spoiled.

If the process that has begun is ignored, then the entire contents of the container may turn into ordinary wine vinegar.

Similarly, bacteria can cause souring of pickled or pickled vegetables.