As you know, weak wines left in incomplete open vessels quickly turn into vinegar. At the same time, turbidity is formed inside such alcoholic beverages, and a delicate thin film is formed on their surface. Wine souring under the influence of bacteria of a special variety. These microorganisms belong to the class of aerobic, and there are many varieties of them.
A bit of history
Of course, people knew that wine could turn into vinegar over time in ancient times. However, how and for what reasons this process occurs, it was found out only in the 60s of the XIX century. In 1867, the causative agent of acetic fermentation was discovered by Louis Pasteur. This famous scientist called his discovered bacterium, which forms a film on the surface of the wine, Mycoderma aceti. Translated, this means "vinegar mushroom." It was later revealed that Mycoderma aceti is not one microorganism, but several types of acetic acid bacteria.
Chemical formulas
The process of digestion of ethyl alcohol with acetic acid microorganisms occurs as 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 creatures, need energy. The conversion of ethyl alcohol to vinegar due to its intensity resembles an anaerobic process. However, this reaction is nevertheless related to aerobic.
After souring the wine, the bacteria in it continue to live. That is, they begin to process vinegar itself. Moreover, such an acid is converted into carbon dioxide (CO 2 ) and water (H 2 O). With anaerobic fermentation, this simply cannot happen. The oxidation in such reactions is always incomplete.
With Mycoderma aceti bacteria, oxidative reactions can occur with the formation of acetic acid and glucose. With such a component, the chemical formula of fermentation is as follows:
In this case, in addition to the vinegar itself, carbon dioxide is also formed. Also in the process of this reaction a little energy is released. In addition to Mycoderma aceti, microorganisms of the Gluconobacter group can be causative agents of acetic fermentation.
What are bacteria
It is not only ethyl alcohol and glucose that can oxidize acetic microorganisms. Such bacteria convert:
Methyl alcohol and higher alcohols are not capable of oxidizing such microorganisms. These 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. In shape and size, such cells can vary significantly, depending on the variety, age, conditions of the nutrient medium, etc.
The optimum reaction temperature for acetic acid fermentation is 15-34 ° C. When the medium is cooled to 12-15 ° C, the development of such microorganisms slows down. Under such conditions, bacteria themselves take the form of short thick sticks. When the temperature rises to 35-45 ° C, some types of acetic acid bacteria can take ugly forms and become like transparent threads with swellings.
In the presence of a large amount of acids in the medium - tartaric, malic, etc., alcohol, and also salts, hypertrophied large microorganisms of this type may appear in it. Also, under such conditions, in acetic acid bacteria, the shell usually begins to slime. In some cases, this process takes on such a serious character that zoogley appears in the environment. In this case, the bacteria themselves in such mucous aggregations are usually quite dispersed.
Life activity
All acetic acid bacteria form films on the surface of the oxidizable substrate. However, depending on the variety of such microorganisms, the latter may have different properties. Some types of bacteria form white-gray thin and delicate films, others - thick leathery ones.
A feature of the microorganisms of this variety is a high degree of mobility. But this property of them to a large extent depends on environmental conditions. At very high temperatures and lack of air, these microorganisms lose their ability to move.
The 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 for the production of natural alcohol vinegar. Also, through such reactions, the following can be performed:
The use of acetic fermentation is also possible in the dairy industry. Bacteria of this variety can be part of the starter cultures used in the preparation, for example, kefir.
The most popular varieties
As already mentioned, Mycoderma aceti is not just one bacterium, but a whole group. For example, the Acet Orleanense variety forms a film on the surface of a wine. Bacteria are very common. On the surface of the wine, it is able to form a silky and rather strong film. Its feature, unlike most representatives 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 bacterium that is why it is usually used to obtain wine vinegar from low alcohol drinks.
Also a very common representative of the group is Acet Schuetzenbachii. This bacterium is used to produce vinegar using fast German technology. It is grown on beech shavings moistened with acidified diluted ethyl alcohol.
Acetic acid bacteria are also widely known:
Acet Aceti, which is a short gram-negative stick that does not form a spore. 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. This bacterium turns yellow in iodine.
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, this variety is painted in blue.
Vinegar uses
This substance, undoubtedly, is the most universal solvent of all known. Vinegar belongs to monobasic aliphatic acids, it is resistant, 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.
By strength, there are three main varieties of acetic acid solutions:
Use of a food solution
Natural alcohol vinegar has found the widest application, of course, in the food industry and in everyday life. In these areas, mainly low concentrated ethanoic acid 3-15% is used.
In the food industry and household, vinegar can be used:
for flavoring dishes;
when baking;
in the preparation of vegetable marinades and pickles;
in the preparation of marinades for frying fish, poultry or meat, etc.
With vinegar, for example, you can eat dumplings. When baking pies and cakes, they extinguish soda. As a result, the dough is filled with bubbles and subsequently rises much better.
Using vinegar, pickles, tomatoes, and eggplant are pickled. Due to the presence of this ingredient, such blanks can retain their nutritional value throughout the cold season. In particular, an acetic acid reaction manifests itself in the fermentation of cabbage.
Use of technical solution
Acetic essence of 70% can also be used in household and food industries for the same purposes. Such a solution, if necessary, is simply diluted to the desired concentration with water or is 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 printing industry;
in the preparation of varnishes, paints, acetone;
in the textile, leather industry, etc.
Where is 100% vinegar 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 to make vinegar for a very long time. The first mention of the practical use of this substance dates back to 3 millennium BC. Vinegar was once used, for example, for the preparation of lead white or jar-copper.
Nowadays, two main technologies can be used to produce this product:
The French method, which allows to obtain the highest quality product. Using this technology, weak grape wines are subjected to acetic fermentation. The process in this case takes several weeks. During this period, among other things, special aromatic substances are formed, which give vinegar its excellent qualities.
German fast method. In this case, using twisted beech chips moistened with acidified alcohol, a very large oxidation surface is preliminarily created.
Vinegar, prepared according to French technology, turns out to be of higher quality. But such a product is also worth it, since it has been manufactured for quite some time, quite expensive.
Portuguese recipe
Some people are interested in how to make wine vinegar with their own hands. This can be done, for example, from the following ingredients:
- dry red wine - 0.75 l;
- grape vinegar - 50-100 ml.
Wine is poured into a large container at the first stage. Next, vinegar 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
You can make such a product from wine quite quickly and without any problems. But it’s even easier to make homemade apple vinegar. The recipe for its preparation in this case will look as follows:
Wash apples, cut into large slices and leave in the air until dark;
squeeze the juice from the pieces;
pour the resulting liquid into glass containers with a narrow neck;
put on rubber medical gloves with a puncture in one finger;
stand the liquid in a warm, dark place for 6 days.
After gloves are inflated, fermenting apple cider vinegar must be poured into a wide bowl. This will speed up the cooking process. The bottle of vinegar should then be transferred again to a warm, dark place and held there for 2 months at a temperature of +27 ° C.
According to this simple recipe, apple cider vinegar at home will not be difficult to do. At the final stage, the finished product must be filtered through cheesecloth into clean bottles and sent for storage in a refrigerator or cellar.