To evaluate the quality of an Espresso you need to rely on your own senses: sight, smell and taste. The test has to be carried out with high accuracy since each judgment is subjective in any case.
COFFEE SENSORY TEST
To analyze the aspect of an Espresso we only need to pour it into a hot coffee cup and immediately analyse the creamy froth. Three elements of the creamy froth are taken into account: consistency (firmness and thickness), persistence (how long it takes to vanish), and color. A creamy froth homogenous in color with streaks indicates an espresso with perfect extraction. It must be compact, thick and long lasting. We can establish the coffee composition on the base of the color and the consistency of the creamy froth: A deep hazelnut creamy froth, also with reddish tinges and small compact bubbles, reveals that the dominant or exclusive blend is Arabica. A dark brown creamy froth, with greyish shade, large and no compact streaks indicates the abundant use of Robusta in the blend.
Taking a drop of espresso, our taste buds define a sweet, acidic and bitter taste. Sweetness is due to not too roasted beans that contain a high percentage of glucose. Acidity derives from the presence of organic acids that decrease during the roasting phase. Bitterness in the finale comes from caffeine, sugar and wood compounds transformation that takes place during the roasting process. Besides these characteristics, which change according to the coffee quality, it’s possible to find a smoothness tactile sensation (roundness and thickness) or a tactile sensation of astringency, due to the wood elements inside the bean causing dryness.
To evaluate the intensity, the finesse, the richness and the persistence of the coffee aroma, we must rely on direct perception and on the nasal duct sensation, taking place after deglutition. While approaching the cup to your nose, hot and humid air will give you a lot of different sensations; these are the most common: roasted: dominant characteristic of every espresso chocolate-like: most desirable aroma in which we can recognize strong cocoa flavours and sometimes hints of vanilla fruit: it is typical of good washed coffees and reminds different fruit scents, especially citrus peanut: negative characteristic flowery: pleasant sensation, typical of very good washed coffee. You can find also a particular aromatic scent grassy: it reminds the fresh grass smell, appreciated if it’s soft and temporary, unpleasant if predominant jute: this scent derives from the wet jute bags in which green coffee beans have been stored straw: smell similar to dried stalks, a typical note of faulty beans unclean water: it’s caused either by dirty filters or by dirty filter holders empyrfeumatic smells: negative characteristic deriving from faulty roasting rancid: this reminds us the smell of ham that has been sliced and left too long or oxidized butter. It’s typical of old coffee, which has been toasted far too long or poorly packaged riato (rio flavour): similar to the cork’s smell of some wines stinker (rotten flowers): it reminds rotten flowers and it’s caused by the fermentation of the coffee fruit not picked on time.