The Perfect Espresso

All the most sophisticated techniques and a skilled barista will never be able to extract a good espresso from a poor blend. Whether a blend or single origin, the coffee must be good, that is, pleasant, sweet, fragrant, aromatic, and leave a pleasant and lasting aftertaste. We must always remember that after drinking a good coffee, we should feel the desire to enjoy another. Within the limits of local habits and tastes, the coffee beans must be roasted just right, because if too dark, it will be more bitter, and if too light, it will be excessively acidic.

The coffee beans can be stored for a long time in the original packaging, whether in a bag or a jar, but once the packaging is opened, the product deteriorates rapidly. To preserve it best, after use, it should be placed in an airtight container and stored in the fridge. The same technique can be adopted at home to store ground coffee, but in any case, even with this caution, the ground coffee is about fifty times more perishable than the whole beans. This is because the grinding process significantly increases the surface area of the coffee exposed to atmospheric oxidation. The barista should never store the ground coffee in the doser for more than a few hours.

THE GRINDER

The normal bar grinder consists of two flat grinding stones stacked on top of each other, with an adjustable distance to choose the right coarseness of the powder. The grind setting needs to be adjusted several times a day due to variations in atmospheric humidity, especially in areas with variable climates: high humidity requires a coarser grind, otherwise the percolation is slow and laboured, resulting in over-extraction; a lack of humidity requires a finer grind. It is advisable to grind only a small amount of coffee at a time to ensure the product is always fresh: it should just cover the wings of the doser. Furthermore, flat grinders operate at high speed, and prolonged operation would overheat the coffee, giving it an unpleasant taste of smoke and burnt. The grinding stones should be replaced approximately every 400 kilograms of coffee. In the case of very lightly roasted coffee, the wear on the grinding stones is more rapid, and they should therefore be replaced more often.

The volumetric doser does not weigh the coffee, but measures a certain volume, which must be prepared and monitored with great accuracy and a certain frequency. The ideal dose would be 7 grams for a single cup and 14 grams for two cups. In the absence of sensitive scales, the calibration of the doser is done by weighing ten doses and adjusting to seven grams. Cleaning the grinder is very important, as coffee residues can become rancid and spoil the taste of the product.

In the modern automatic espresso machine, the heart is constituted by the boiler in which the water is heated. It is important to remember that the water in the boiler is not used to make the coffee, but, dispensed from the appropriate tap, will be used for tea and other purposes. Steam forms in the upper part of the boiler, which, via the other tap present on the machine, will be used to heat milk and other liquids. The water for the coffee, pushed by a pump at a pressure of 9 BAR (atmospheres), passes through a heat exchanger within the boiler where it is heated and maintained at the correct temperature of approximately 90°.

Filled the filter from the doser, the coffee should be pressed with a force of 10-20 kilos. Generally, the skilled operator will adjust by pressing the coffee in a way that compensates for any small grinding defects. Before attaching it to the machine group, the edge of the portafilter should be cleaned, as coffee residues could limit the closure (resulting in a loss of pressure) and form deposits on the seal, which could deteriorate more quickly. The espresso should flow out steadily and have a "mouse tail"; the cup should be well heated but should not burn the lips of the customer.

Maintenance is essential for achieving a perfect espresso: the grinder's hopper must be washed regularly to remove any traces of grease. The inside of the grinder should be carefully brushed to eliminate all residues, while the doser must be cleaned with a brush. Every evening, filters must be removed and washed from the portafilters of the machine; the coupling area should be meticulously cleaned with a metal brush. It is preferable to leave the machine on overnight, especially to avoid excessive limescale formation; in this regard, it is crucial to check the water softener frequently. Limescale deposits restrict the flow of water, lowering the temperature and compromising the success of the extraction.

Extraction refers to a rapid process established according to the degree of grinding, water temperature, pressure, and contact time between the water and the coffee grounds.

For espresso, it refers to a small cup of concentrated coffee, extracted from freshly ground coffee beans, and must correspond to the following average parameters:

• Quantity of coffee required 7g
• Water temperature 90° C
• Water pressure 9 BAR
• Compression in the filter approximately 15 kg
• Extraction time 25 seconds
• Quantity in the cup 25 ml
• Temperature of the empty cup 60° C