Acetic acid fermentation: pathogens and practical use

2024 Author: Howard Calhoun | [email protected]. Last modified: 2024-01-15 14:07

As you know, weak wines left in incomplete open vessels quickly turn into vinegar. At the same time, turbidity forms inside such alcoholic beverages, and a delicate thin film forms on their surface. Souring of wine occurs under the action of bacteria of a special variety. These microorganisms belong to the aerobic class, and there are many varieties of them.

A bit of history

The fact that wine can eventually turn into vinegar, people, of course, knew in ancient times. However, how and for what reasons this process takes place was clarified only in the 60s of the XIX century. In 1867, the causative agent of acetic fermentation was discovered by Louis Pasteur. This famous scientist named the bacterium he discovered, which forms a film on the surface of wine, Mycoderma aceti. Translated, it means "vinegar mushroom". Later, it was found that Mycoderma aceti is not one microorganism, but several types of acetic acid bacteria.

Chemical formulas

The process of fermentation of ethyl alcohol by acetic acid microorganisms occursas follows:

CH3CH2OH + O2 → CH3COOH + H2O + E

That is, acetic fermentation in wine occurs with its dehydrogenation. The energy effect during the passage of such a reaction is minimal. Therefore, acetic acid bacteria have to oxidize a very large amount of alcohol. After all, they, like any other living beings, need energy. The conversion of ethyl alcohol to vinegar, due to its intensity, resembles an anaerobic process. However, this reaction is still aerobic.

After the souring of the wine, the bacteria in it continue their vital activity. That is, they begin to process the vinegar itself. In this case, such an acid is converted into carbon dioxide (CO₂) and water (H_{2O). With anaerobic fermentation, this simply cannot happen. Oxidation in such reactions is always incomplete.}

With the participation of the bacteria Mycoderma aceti, oxidative reactions can occur with the formation of acetic acid and with glucose. With such a component, the chemical formula for fermentation is as follows:

C6H12O6 + 2O2 → 2CH3COOH + 2CO2↑ + E.

In this case, in addition to the vinegar itself, carbon dioxide is also formed. Also, some energy is released during this reaction. In addition to Mycoderma aceti, microorganisms of the Gluconobacter group can be causative agents of acetic fermentation.

What are bacteria

Not only ethyl alcohol and glucose are capable of oxidizing acetic acid microorganisms. Such bacteriaturn:

• propyl alcohol to propyl acid;
• butyl to oil.

Methyl alcohol, as well as higher alcohols, are not capable of oxidizing such microorganisms. Such bacteria are in most cases rod-shaped short cells 2-1.5x1.0 long. A feature of these microorganisms is that they do not form spores. The shape and size of such cells can vary significantly, depending on the variety, age, conditions of the nutrient medium, etc.

The optimum reaction temperature for acetic fermentation is 15-34 °C. When the medium is cooled to 12-15 °C, the development of such microorganisms slows down. The bacteria themselves under such conditions take the form of short thick rods. When the temperature rises to 35-45 ° C, some types of acetic acid bacteria can take on ugly shapes and become like transparent threads with swellings.

If there is a large amount of acids in the medium - tartaric, malic, etc., alcohol, as well as s alts, hypertrophied large microorganisms of this type may appear in it. Also, under such conditions, the shell of acetic acid bacteria usually begins to slough off. In some cases, this process becomes so serious that zoogles appear in the environment. At the same time, the bacteria themselves in such mucous accumulations are usually quite scattered.

Life activity

All acetic acid bacteria form films on the surface of the oxidized substrate. However, depending on the typesuch microorganisms, the latter may have different properties. Some types of bacteria form white-gray thin and delicate films, others - thick, leathery.

A feature of microorganisms of this variety is a high degree of mobility. But this property of them largely depends on environmental conditions. At very high temperatures and lack of air, these microorganisms lose their ability to move.

Bacteria that cause acetic acid fermentation can live on vegetables, fruits, juices, vinegar, alcoholic beverages.

Application

The process of oxidation of ethyl alcohol and glucose is used in industry mainly to obtain natural alcohol vinegar. Also through such reactions can be produced:

• apple cider vinegar;
• wine.

Use of acetic fermentation is possible in the dairy industry. Bacteria of this variety can be part of the starter cultures used in the preparation of, for example, kefir.

Most popular varieties

As already mentioned, Mycoderma aceti is not one bacterium, but a whole group. On the surface of the wine, for example, a variety of Acet Orleanense forms a film. The bacterium is very common. On the surface of the wine, it is able to form a silky and rather durable film. Its feature, unlike most members of the group, is that it is able to withstand a very large amount of alcohol in the environment - up to 12%. It is this bacteriumtherefore, it is usually used to obtain wine vinegar from low-alcohol drinks.

Also a very common member of the group is Acet Schuetzenbachii. This bacterium is used to produce vinegar using rapid German technology. It is grown on beech shavings moistened with acidified diluted ethyl alcohol.

Acetic acid bacteria are also quite widely known:

1. Acet Aceti, which is a short gram-negative rod that does not form spores. This bacterium is immobile, creates chains and is able to withstand up to 11% alcohol in water. Acet aceti forms a film on the surface of the beer. Iodine turns this bacterium yellow.
2. Acet Pasteurianum. This variety is similar in shape and characteristics to Acet Aceti. But on the surface of drinks in the process of acetic acid fermentation, it forms a folded film. Iodine turns this variety blue.

Sphere of use of vinegar

This substance is undoubtedly the most versatile solvent known. Vinegar belongs to monobasic aliphatic acids, it is stable, cheap and affordable. Most substances of organic origin are capable of dissolving this substance. In another way, vinegar is called ethanoic acid. It can be used in various fields of human activity.

According to the strength, there are three main types of acetic acid solutions:

• food (actually vinegar) with a strength of 3-15%;
• technical (essence) - 70-80%;
• ice ice - 100%.

Use food solution

The most widely used natural alcohol vinegar found, of course, in the food industry and everyday life. These areas mainly use low-concentration ethanoic acid 3-15%.

In the food industry and everyday life, vinegar can be used:

• for flavoring dishes;
• when baking;
• when preparing vegetable marinades and pickles;
• when preparing marinades for frying fish, poultry or meat, etc.

With vinegar, for example, you can eat dumplings. When baking pies and cakes, they quench soda. As a result, the dough is filled with bubbles and subsequently rises much better.

Cucumbers, tomatoes, eggplants are pickled using vinegar. Due to the presence of this ingredient, such preparations can retain their nutritional value throughout the cold season. The acetic acid reaction is especially pronounced when sauerkraut is sauerkraut.

Using technical mortar

Acetic essence 70% can also be used in everyday life and the food industry for the same purpose. Such a solution, if necessary, is simply diluted to the desired concentration with water or used in small quantities. Also technical acetic acid can be used:

• in medicine in the preparation of medicines (for example,aspirin);
• in the pulp and paper industry;
• when preparing varnishes, paints, acetone;
• in the textile, leather industry, etc.

Where one hundred percent vinegar is used

Glacial anhydrous acid has a melting point of just over 16°C. At lower temperatures, it begins to crystallize. That is why she got her name. Like the technical variety, glacial acetic acid can be used, for example, in the manufacture of medicines or solvents.

Cooking Methods

People have learned how to make vinegar for a very long time. The first mention of the practical use of this substance dates back to the 3rd millennium BC. Vinegar was once used, for example, to make white lead or verdigris.

Today, two main technologies can be used to produce this product:

1. French method for the highest quality product. When using this technology, weak grape wines are subjected to acetic acid fermentation. The process in this case takes several weeks. During this period, among other things, special aromatic substances are formed, which give the vinegar its excellent qualities.
2. German fast method. In this case, using twisted beech wood chips moistened with acidified alcohol, a very large oxidation surface is pre-created.

French-style vinegartechnology, better quality. But such a product is also worth it, since it is made for quite a long time, quite expensive.

Portuguese recipe

Some people are also interested in how to make wine vinegar with your own hands. This can be done, for example, from the following ingredients:

• dry red wine - 0.75 l;
• grape vinegar - 50-100 ml.

Wine at the first stage is poured into a large container. Next, vinegar-sourdough is added to it. The fermentation process using these ingredients lasts about 30 days.

How to make apple cider vinegar at home: a simple recipe

From wine you can prepare such a product quickly enough and without any problems. But it's even easier to make homemade apple cider vinegar. The recipe for its preparation in this case will look like this:

• wash apples, cut into large slices and leave in the air until dark;
• squeeze juice from pieces;
• pour the resulting liquid into glass containers with a narrow neck;
• put rubber medical gloves on the container with a puncture in one finger;
• keep the liquid in a warm dark place for 6 days.

After the gloves are inflated, fermenting apple cider vinegar should be poured into a wide bowl. This will speed up the cooking process of the product. The container with vinegar should then be transferred again to a warm, dark place and kept there for 2 months attemperature +27 °С.

This simple homemade apple cider vinegar recipe is easy to make. The finished product at the final stage must be filtered through gauze into clean bottles and sent for storage in the refrigerator or cellar.