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Vinegar is a ubiquitous ingredient in most kitchens around the world. From French to Italian cuisine, and from Asian to African, virtually all of them use vinegar in their preparations, in one way or another. This bitter liquid has been known and used for more than 5,000 years, but the discovery of its chemical composition is much more recent. In the following sections we will explore how vinegar is made, the different types of vinegar that exist, and the chemical composition of one of the most used ingredients in salads around the world.
Vinegar is an aqueous solution of acetic acid.
The characteristic pungent odor of vinegar, as well as its bitter and sour taste, is due to the fact that vinegar is a dilute aqueous solution of ethanoic or acetic acid . This is an organic compound belonging to the group of carboxylic acids, and its molecular formula is CH 3 COOH. The structure of acetic acid is presented below:
Concentration of acetic acid in vinegar
The acetic acid content varies greatly from one vinegar to another. In most commercial vinegars for culinary use, the concentration is between 3% and 5%. However, there are other types of vinegar that have higher concentrations, being able to reach very high values, even above 20%. This depends on the type of vinegar in question, the method of preparation and whether or not it is distilled.
Vinegar preparation processes
Vinegar is generally prepared by a double fermentation process. In all cases, the starting material is a sugar solution that is fermented with a yeast to convert all of the sugar to ethyl alcohol or ethanol. The alcoholic solution is then fermented by special strains of bacteria that oxidize the alcohol into acetic acid.
In some cases the fermentation of alcohol occurs spontaneously and even unwanted. For example, it is common for wines to ferment sour and this fermented wine solution is nothing more than vinegar. In fact, the very word vinegar comes from a French expression that literally means “sour wine.”
The sweet mixture that is used as raw material for alcoholic fermentation is very varied and depends mainly on local availability. For example, grapes are plentiful in France and Italy, so much of the vinegar produced in those parts of the world is made from grape must.
On the other hand, in Asian countries it is much easier to get rice, which is why it has been customary there for centuries to produce rice vinegar. On the other hand, large quantities of sugar cane are produced in the Americas, the juice of which is used in the large-scale production of ethyl alcohol. In these countries it is also customary to distill the alcohol before the second fermentation, resulting in a white vinegar that contains almost exclusively acetic acid.
types of vinegar
As you can imagine, such a variety of raw materials and production processes, in addition to the availability of different strains of microorganisms to carry out the two fermentation processes, results in the existence of different types of vinegar. Some of the most common are:
white vinegar
It is a purified version of vinegar that has undergone distillation to separate the acetic acid from other components of the original ferment. This type of vinegar is completely colorless (not really white) and can be made to virtually any desired concentration, since distillation yields nearly pure acetic acid. However, commercial presentations, particularly those intended for human consumption, do not exceed 10%.
wine vinegars
These vinegars are prepared through the direct fermentation of different types of wine. Thus, there are red wine vinegars, white wine vinegars, vinegars from specific grape strains, etc. Some wine vinegars are stored in oak barrels in a similar way to the wine from which they come. This adds a set of phenolic organic compounds to the composition of the vinegar, making it more aromatic and with a more intense flavor.
balsamic vinegar
This is a special type of wine vinegar that is mixed with a combination of cooked and concentrated must from different types of wine. The result is a thick mixture that contains at least 20% must, which gives it its characteristic texture, as well as a sweet flavor and an acetic acid content of at least 6%. On the other hand, some manufacturers also add caramel to intensify its flavor and sweetness.
rice vinegar
As its name indicates, it is prepared from the fermentation of a homogenized mixture of cooked rice. It is nearly colorless and is generally more acidic than wine vinegars. It is very commonly used in Asia, particularly in Japanese food.
In addition to these vinegars, there are also others that receive designation of origin, such as Jerez vinegar and Huelva county vinegar.
Other components of vinegar
In addition to acetic acid, the different types of vinegar may also contain other minor components, but these provide each vinegar with a flavor and aroma that distinguishes it from all the others. Some of these compounds are:
phenolic derivatives
They come mainly from contact with wooden barrels during the aging of wine and balsamic vinegars. Some examples are gallic acid and its esters, various catechins and various derivatives of reveratrol, among others.
tartaric acid
This acid is found naturally in many fruits, including grapes. Consequently, most undistilled vinegars contain variable amounts of tartaric acid and other similar organic compounds.
citric acid
This is another example of a compound present in many fruits that are used for the preparation of natural vinegars and therefore remain in the vinegar after its manufacture.
sugars
Some types of vinegar have certain amounts of sugars that represent less than 1% of their mass, while most vinegars do not contain any sugar. However, balsamic vinegar, because it is mixed with grape must, has a much higher concentration of sugars.
References
- Adams. MR (2014). Vinegar. Retrieved from https://www.sciencedirect.com/science/article/pii/B9780123847300003487
- Chang, R., & Goldsby, K. (2013). CHEMISTRY (11th ed.). McGraw-Hill Interamericana de España SL
- vinegar . (2021). Map.Gov.Es. https://www.mapa.gob.es/es/ministerio/servicios/informacion/vinagre_tcm30-102374.pdf
- vinegar . (nd-b). Chemistry.is. https://www.quimica.es/enciclopedia/Vinagre.html
- vinegar . (2021, July 6). The Nutrition Source. https://www.hsph.harvard.edu/nutritionsource/food-features/vinegar/
