Espresso is created by forcing under pressure near boiling water through finely ground compacted coffee beans. It is much thicker and more concentrated than coffees brewed by other methods. It consists of dissolved substances as well as suspended solids. To top it off it should have a layer of crema (cream). This is produced by the high pressure water as it is forced through the coffee grind. It is an emulsion of oils from the coffee and the water.
This process creates a distinctive type of coffee with a particular flavour. It is a bitter sweet flavour and must be served not too hot. The high pressure extracts more caffeine and other alkaloids from the grind than would other forms of brewing. A good cup is very concentrated but because of the size of the serving it has overall less caffeine than a standard normal filter coffee. An espresso is served as a 60ml cup compared to a filter coffee of 240ml. The caffeine content is between 80mg and 150mg compared to the 95mg to 200mg of filter coffee.
Espresso brewing requires a skilled barista, barkeep in Italian, and en expensive machine to brew the drink. It requires the barista to create the drink on demand, ie the coffee has to be freshly ground and the serving has to be created while the customer waits. Nothing can be prepared in advance. It is therefore not like filter coffee that can be easily and quickly created at home. It is thus suited for the coffee-houses and the culture and traditions that have grown up around it.
It has become the basis for many other speciality coffees which have aid in its spread around the world. It is the basis for traditional Italian macchiattos and cappuccinos to American-style flavoured lattes, mochas, and other blended coffees.
Coffee producing countries use a quarter of all coffee produced
An astounding $80 billion plus is spent annually on coffee of all forms. That is 14,400 000 000 kg of coffee produced each year.
Espresso is a dark, thick aromatic brew, with a dark reddish-brown foam, called crema.
To create or brew espresso the coffee beans have to be finely ground. This step is important, It has to be just right to create a big enough surface area on the coffee grinds allowing an efficient extraction process. This is further enhanced by tamping down the grind to promote the waters even penetration of the grounds. The water has to be close to boiling but not boiling. It is then forced under pressure through the coffee grinds. This process dissolves alkaloids and oils extracts solid particles forming a syrupy liquid. The oils are emulsified into a colloid called the crema. This only occurs in this process and no other coffee brewing process.
A serving of espresso is called a shot. In the days before electric pressure pumps the barista had to create the pressure manually using a handle linked to a systems of levers and a spring loaded piston, so it became known as ‘pulling’ a shot when serving an espresso.
There is no specific coffee bean that is used in the brewing process, any bean or roast level is fine. It must be freshly ground though. The darkness or otherwise of the roast is dependent on taste. Certain levels of colour are endemic in certain areas. Southern Italy you will find that the dark roast is the standard while it gets lighter as you move up north. The Americans have added their spin to this brew by adding syrups, cream and spices to the brew, enough to give any true aficionado the shivers.