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 The secret of using acids to flavor food has been known since antiquity. The oldest acid tested is vinegar. Even the ancient Greeks used it. No other acids were known then. The name "vinegar" comes from the Greek word "oxyus" - sour. There was a time when vinegar was highly prized. According to the historian Pliny, a special drink was prepared for the Egyptian Queen Cleopatra by dissolving pearls in vinegar.
Perhaps, such a drink does not seem very appetizing in our time. We have other cases when we feel the need for vinegar: with its help marinades, mustard, satsivi are prepared, herring is seasoned, salads ...
Where does vinegar come from? How and from what is it made?
Experience has long suggested that if a weak wine or beer is left open for a while, it turns sour, turns into vinegar. The explanation for this came when people got acquainted with microbes. It turned out that the transformation of wine or any other alcoholic liquid into vinegar occurs with the participation of special acetic acid bacteria or, as they are not quite accurately called, vinegar fungi. Once in a liquid containing alcohol, bacteria multiply rapidly, and then oxidize the alcohol and convert it into acetic acid.
This method is still used to obtain food vinegar. To do this, in large wooden vats, an aqueous solution of alcohol is sprayed onto the beech shavings, into which a previously derived culture of bacteria is introduced. From below, air is blown into the vat to oxidize alcohol by bacteria. Food vinegar contains 3 to 10 percent acetic acid. Depending on what served as the raw material for the production of vinegar, there are wine, alcohol, fruit and even beer and honey vinegar. Flavored vinegar is also produced, which is infused mainly on spices and aromatic plants (tarragon, celery, black currant leaves).
During the Middle Ages, alchemists obtained vinegar by dry distillation of wood. It is known that if a tree is heated without air access, it does not burn, but begins to release various volatile compounds. The liquid obtained by dry distillation of wood, the so-called "liquid", contains about 10 percent acetic acid, 1-2 percent wood methyl alcohol, 0.5 percent acetone and some other impurities. This liquid is treated with lime and thus acetic acid is released, which is called acetic essence.
Recently, they began to obtain acetic acid by a purely chemical method from petroleum gases. Even 80 years ago, the Russian chemist M.G. Kucherov developed a reaction that formed the basis for the production of synthetic acid. To do this, acetylene gas is emitted from natural or petroleum gases, which, together with water, forms a chemical compound - acetaldehyde, then it is oxidized, i.e. oxygen is added to it, and it is converted into acetic acid.
This method is still widely used. However, vinegar has long been no longer the only acid for flavoring food and food. Tartaric acid, lactic acid, citric acid, etc. have also appeared and found their application. And recently, malic acid has also been used.
Judging by the names, one might think that tartaric acid is obtained from wine, lactic acid from milk, and malic acid, of course, from apples. But this is far from the case! Tartaric acid alone, or, as it is called otherwise, tartaric acid, to some extent justifies its name. It is produced from "tartar", that is, from a special salt that settles on the inner surface of wine barrels.
But lactic acid has nothing to do with milk.The raw material for it is the waste of beet sugar production, the so-called molasses. In this case, microorganisms play an important role, but not acetic acid bacteria, but others - lactic acid bacteria.
The production of citric acid is curious. It was once actually made from lemons. But this is too expensive and unprofitable way. Indeed, in the best case, lemon juice contains 6-7 percent citric acid. A whole ton of lemons had to be processed to get 1.5-2 kilograms of crystalline acid!
Even countries with huge lemon groves in bloom could not supply as many lemons as needed to get enough acid. And the same clever inventive chemistry came to the rescue. Chemists have proposed a new way of producing citric acid from ... sugar. At first glance, it is strange: sour from sweet! However, for more than three decades, this is how citric acid has been produced. And again, invisible chemists - microorganisms - are at work. This time, molds are involved in the production of acid.
There is a black mold (Aspergillus niger) that specialized in the production of citric acid.
In large and flat vessels, like plates, millions of black fungi "work" in peace and quiet. First, they multiply on a special nutrient medium, forming a continuous black film. Then the liquid under the film is removed and a sugar solution is pumped in instead, from which the fungi produce citric acid. This process is long - about ten days, until the fungi "get tired" of processing sugar. Then the real chemists get to work.
They use chalk to bind citric acid and separate it from the liquid, and then purify the acid and make it crystallize.
Currently, citric acid is obtained not by a film, but by a deep method. Due to this, the fungi with their threads permeate the sugar solution in a large vessel and act somewhat faster.
The method of making acid not from sugar has already been mastered, but from the same waste - molasses, from which lactic acid is made. After all, molasses contains almost 50 percent sugar, why waste granulated sugar? But it is more profitable to get citric acid even from sugar than from lemons. Scientists have calculated that the yield of 1 lemons from 1 hectare of plantation area gives an average of 400 kilograms of crystalline acid, and 1600 kilograms of sugar obtained from a hectare of beet fields can be produced.
So, acetic acid is obtained from wood, citric acid from sugar, and malic acid from what? Extracting malic acid from apples or barberries is even less profitable than extracting citric acid from lemons. Therefore, malic acid has not been used in the food industry until recently. She just wasn't there. Scientists from the Research Institute of the Food Industry proposed to extract malic acid from coal, or rather from chemical compounds that are obtained during the processing of coal. Such a well-known chemical compound is benzene. The vapors of benzene are oxidized with oxygen, and it is converted into another substance, the so-called maleic anhydride.
As an accelerator of this process, a mixture of oxides of three metals - vanadium, molybdenum and cobalt, taken in certain proportions, is used. The maleic anhydride thus obtained is smelted, purified and converted into maleic acid. And now it is only necessary to add a molecule of water to each molecule of maleic acid and it turns into malic acid. This transition is accelerated in the presence of sulfuric acid, which in this case is also a catalyst. Then malic acid is isolated, purified in much the same way as citric acid. Synthetic malic acid is produced at the Kharkov Food Acid Plant. This is one of those chemical wonders of modern chemistry that we never cease to be amazed at.
The sour lemonade, sour sweets contain the magic of chemistry, which allowed the unsightly black coal to turn into transparent crystals - carriers of a pleasant sour taste. We also produce other food acids. One of them (trioxyglutaric) is obtained from ... cotton husk; it is produced at the Fergana hydrolysis plant. It has long been proven that trioxyglutaric acid is completely harmless, and it is used as a food product.
Another acid (adipic acid) is still being tested as food. It is a crystalline substance and is obtained from phenol. So far, this acid serves only as a raw material for the production of synthetic fiber - nylon. It has been found that adipic acid is harmless and has a pleasant sour taste. In the USA, in Canada, in some other countries, its use in the food industry is allowed. At the All-Union Scientific Research Institute of the Canning Industry, we also conducted experiments on the use of adipic acid in the production of canned fruit. In the near future, this acid may find its use not only in the production of nylon, but also useful for acidifying lemonades, monpensier and some other food products.
Volper I.N. Legends and to be about products
Vinegar - selection and use
Vinegar - use in bread dough
The use of vinegar essence in the marinade 70% (conversion of the essence to vinegar)
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