What does coffee smell like?
Coffee is a drink made from roasted seeds (grains) of several plant species belonging to the genus Coffee (Coffea) of the Madder family (Rubiaceae).
There are more than 90 species of plants belonging to the genus of coffee (Coffea). There are two main commercially used types of coffee trees and, accordingly, beans obtained from the fruits of these trees: Coffea arabica L. - Arabica and Coffea canephora Pierre ex Froehn., Or Robusta, sometimes called Congolese coffee. According to different estimates, these two types account for up to 98% of the coffee produced. This volume is divided in the ratio of 70% - Arabica, 30% - Robusta. The remaining types of coffee account for only 2% of world production. The most common type of coffee, Arabica, grows at an altitude of 900 to 2000 meters above sea level. Grains, as a rule, have an oblong shape, a smooth surface, a slightly curved “S” -shaped line, in which usually unburned particles of a coffee berry remain after light roasting. Robusta is a fast-growing and more resistant to pests than arabica, and grows from about 0 to 600 m above sea level, primarily in tropical regions of Africa, India and Indonesia. Grains have a rounded shape, color - from light brown to grayish-green. Robusta is usually considered less refined coffee in terms of aroma. At the same time, it contains more caffeine, and is also often used in espresso blends, which allows for better coffee crema and reduces the cost of the blend.
In specialty stores you can find green, unroasted coffee beans. Their "non-coffee" aroma is capable of telling a lot of things - someone describes it as grassy, for someone it reminds strong brewed green tea, and for some it seems that it smells of raw beans.
Imagine an odorless coffee. What remains? Sour-bitter, astringent brown liquid. Where does this unique aroma, which constitutes the whole essence of this drink, come from, and what does it depend on?
Attractive and appetizing "firm" aroma of coffee gets due to volatile compounds which are formed in the process of roasting. They arise due to the Maillard reaction - a chemical reaction between sugars and amino acids that occurs when heated and leads to a whole set of interrelated chemical transformations. The final taste and aroma occurs depending on the composition and ratio of substances accumulated as a result. By the way, the same reaction is responsible for the formation of such compounds when frying meat or baking bread.
To the presence of different components in the air around us, we are sensitive to varying degrees. Each odorous substance has an odor perception threshold, that is, the minimum concentration that causes olfactory sensations. In the process of evolution, our sense of smell developed in such a way as to easily identify life-threatening compounds. It is not surprising that the human nose is very sensitive to putrescine and kadaverin, which determine the smell of rotten meat, and highly toxic hydrogen sulfide (the smell of rotten eggs) our olfactory organs catch already in a concentration of 0.000012 mg / l , while the deadly poisoning can only be obtained when 1.0 mg / l . However, we can feel some familiar harmless smells only when the surrounding air is already very saturated with them.
Each of the flavors of individual substances can be given a characteristic: fruity, floral, earthy, coniferous, spicy, and so on. But the characteristic smell of food will be determined by their complex mixture, consisting of several tens or hundreds of such flavors.
About 800 substances are involved in the formation of coffee smell. All of them are perceived by olfactory receptors in different concentrations and with different intensity, and, despite the fact that the main components in this mixture of smells are about 20, the characteristic aroma results only in the presence of seemingly insignificant components. To determine these substances in the composition of coffee, the method of gas chromatography was used (for more information on chromatography, see Science and Life, No. 2, 1998 ) It turned out that in this set of compounds only a few in their pure form are recognized as “smelling coffee”. For example, the purely found furaneol has a milky caramel aroma, diacetyl - butter aroma, damascenone - roses and prunes, and 2-methylfuran, carbon disulfide, propionic and acetic aldehydes smell of fruit.
More specific shades give 3-mercapto-3-methylbutyl formate , 3-methylbutanal and methylpropanal , which are defined as burning or roasting smells, guaiacol gives a smoky smoky flavor, and 2-ethyl-3,5-dimethylpyrazine gives a nut-woody flavor.
However, there are components in the coffee aroma that have not very pleasant smells: seaweed (dimethyl sulfide), musty, earthy smell of compost (2-methyl isobornol), smell of rotten cabbage (methyl mercaptan) and gasoline (thiophene), as well as many other characterized as unpleasant, harsh, and even suffocating. But, despite the seeming unacceptability, without them the aroma of coffee would not be so full, so many-sided and interesting.
It should be noted that the chemical composition of different types of coffee is different due to the different concentration of the main components. The final aroma will also be affected by the roasting time, its temperature, and the method of further storage of the grains, since most of the substances responsible for the specific coffee aroma are very unstable and are lost due to evaporation or interaction with other compounds.
Therefore, in order to feel the diversity of coffee aroma, try to drink fresh, freshly ground and freshly brewed coffee, and do not miss the opportunity to treat yourself to different varieties. After all, the more and the closer we get to different flavors, the more we perceive and the better we will know them in the future.