The full-bodied effect is determined by a certain density, due to the presence of oily emulsions and insoluble substances (called colloids) in the extract. These substances give the drink considerable viscosity, plus a superlative degree of aroma and “body”.
The consistency of the creamy head is superb, with a compact, fine grain and no gaps giving a glimpse of the black coffee beneath.
The first peculiarity is the foam that sits on top of every good espresso. It should be 3-4mm thick, in order to retain the volatile substances. Even with just the naked eye, we can single out the dominant coffee varieties in an espresso by looking at the texture and colour of the foam.
If the crema is nut-coloured, tending towards pale red, with dark brown streaks and a fine-weave texture, the espresso has been made using Arabica coffee. Alternatively, if it is brown with grey shades and has an open-weave texture, with larger bubbles, it indicates an espresso made with Robusta coffee.
Coffee taste is the result of three fundamental elements: the sensations of bitterness, acidity and sweetness.
Our sense of taste uses our taste buds to recognise and distinguish the flavours in the extract, and determine their intensity.
The bitterness of coffee can be defined as a ”macro-sensation” since it is the main flavour in the black beverage.
The second macro-sensation in coffee is acidity, perceived as a pleasant tingling sensation, a sort of “pseudo-freshness”.
Coffee savour (its light, natural sweetness) is a desirable component of a well-made espresso (perfect roasting, grinding and extraction).
An espresso must offer a balanced, harmonious taste with no single flavour prevailing over the others, unless there are specific preferences.
Thousands of scent molecules give an espresso its famous, intense aroma.
Our sense of smell can perceive numerous aromatic characteristics - both the positive coffee qualities and the defects. A myriad of volatile aromatic substances, derived from the roasting process, give the espresso its typical, scented, “fragrance of the roast”.
Depending on the variety, quality and preparation, from this aromatic base we can perceive the scent of caramel and cereals that give coffee the fragrance of toast, biscuits or confectionery, or there may be slight hints of butter and vanilla and the smell of cacao, evoking chocolate in all its delicious forms.
The sophisticated fruity aromas of coffee bring to mind fresh citrus tones, but also dried fruit or flower fragrances. The coffee foam can release hints of roasted walnuts, almonds and hazelnuts.
Or the aromas can range from tones of oriental essences to the austere scent of seasoned wood and spices such as pepper, tobacco and rhubarb.