The perfect barista doesn't exist. At least, there are very few who can call themselves that, in all honesty. The professional barista must be knowledgeable in a variety of areas: in addition to operating the register, they have to keep the bar tidy and clean, deal with the customers in a friendly manner, but most importantly... they must be able to serve a good espresso.
Presenting a good espresso requires a great deal of passion. The right balance of ingredients will produce a delicious little cup of espresso, something that can only be achieved if it's prepared with care. If you have acquired a good coffee machine, you can further determine the quality by how, and how fast, the coffee comes out of the machine.
If the coffee comes out of the machine at high speed, it results in a cup with little flavour and aroma, full of bubbles and with little body. The opposite is not desirable either. Coffee that comes out of the machine with difficulty is bitter, dark in colour, and probably means that the coffee machine needs to be checked, particularly the pressure. A middle way is therefore desirable for a good espresso. In addition, it goes without saying that the machine should always be clean. Furthermore, the key to a good espresso is the combination of a good temperature of water, and the proper grinding and tamping of the coffee.
In Italy, the large amounts of coffee are usually made according to the guidelines of the Istituto Nazionale Espresso Italiano, which monitors the quality of the espresso. According to this institute, the perfect espresso is made with 6 to 7 grams of finely ground arabica coffee beans. For exactly 30 seconds, 30 ml of water (or sometimes even less) must be pressed through, at the exact temperature of 88 °C.
Ultimately, a cup of espresso may contain no more than 20 to 30 ml of liquid. The froth must be dark brown in colour and have a fine texture. The coffee must have a strong smell. The flavour must be round and bold, with a good balance between bitter and sour.