Coffee taste
The coffee flavor on your lips

Coffee taste

To analyze the taste of coffee, chemists studying the aromas that emerge during the roasting beans, using gas chromatography and olfactive measurement, using professionals testers smelling samples and identify the constituents of a mixture.

Mass spectrometry provides the chemical nature of each substance fragrant. When you breathe constituents separated by spectrometry, we recognize the smell of roses, Darjeeling tea, chocolate, vanilla and violet, or that of the truffle, soup, cheese, sweat , Confectionery and even the smell of cat, which diluted recalls the smell of a white wine, but concentrated, is disgusting.

We generally notice the dominant smells. Imagine that you listen the recording of a choir of 800 singers (800 chemical species of coffee), among whom are the powerful voice of Jessye Norman, from Luciano Pavarotti and other virtuosos, who dominate the whole . When the volume is low, the highest votes are the only ones to emerge. Similarly, when it dilutes the flavor of coffee, only compounds persist most intense. Unfortunately, the odorous molecules in a sample of coffee are those that emit defective beans.
Molecules, such as ethylbutanoate and ethylglycolate responsible for the unpleasant aroma of coffee beans immature, may spoil a cup of coffee. Similarly, the methylisobornéol and trichloroanisol give robusta coffee smell characteristic of land. The trichloroanisol, also appointed a taste for Rio because he was discovered for the first time in cafes grown in the outskirts of Rio de Janeiro, may also be present in wines that taste like cork. The human olfactory system is extremely sensitive to this substance; we able to perceive six millionth of a billionth of a gram per milliliter.


The last step in preparing a cup of espresso is the extraction of hot water aromatic compounds present in the ground coffee. The interaction of water with ground coffee when its prepared with a coffee filter or an espresso machine. When preparing a coffee filter water pass through a cluster of little compact ground coffee particles of average size. During the four to six minutes of contact with boiling water, most soluble substances present in roasted coffee dissolves in water as many species acids and caffeine are drawn into the cup. Instead, the percolation time much shorter used for the preparation of an espresso allowing less acid and only 60 to 70 per cent of caffeine.


The preparation of an espresso requires a machine where water is heated to between 92 and 94 ° C at a pressure of nine atmospheres. The ground coffee is placed in a small receptacle holed. The particles adhere compacted with a thin film of viscous oil. The set is a dense maze of tiny air ducts. The hydraulic resistance of such an assembly is slightly less than the pressure of hot water so that liquid flows at a speed of the order of one milliliter per second.


The percolation ideal time for making an espresso is 30 seconds. In 30 seconds, a server prepares 30 milliliters of coffee tight, covered by the essential foam. If the foam is clear, this means that the extraction has not been sufficient, probably because the draft was too rough, the temperature was too low or the extraction time is too short. If the cream is very dark and it is "holes" in its center, this means that the draft was too thin or too much coffee. An espresso whose extraction was too long presents large white foam with bubbles, in which case the water was probably too hot. When there is just a little foam at the center of the cup is that the extraction time was too long.


What are the other components released by the extraction? The percolation brings substances to the surface, such as oil responsible for aromas and fragments of cells constituting coffee beans. The high pressure prevailing in the espresso machine creates an emulsion between oil and water, so that a cup contains about 100 milligrams of flavored oil. Carbon dioxide is released from the pores of cell walls in the powder, and the result is a slight effervescence.


Taking into account all factors cited, an espresso is a multiphase colloidal system, it’s a fluid where water molecules are linked with bubbles of gas, oil droplets and particles suspended (all measured less than five microns). The suspension gives the drink the "body", a high viscosity and low surface tension. An espresso covers language and continues to release its flavors dissolved in the volatile oil emulsion: we can still perceive the flavor and aroma of an espresso for about twenty minutes after the cup was drunk and it does not need to know the details of the chemistry of coffee to appreciate the flavor.