An espresso machine is a specialized piece of coffee-making equipment used to create a very strong Italian coffee drink called espresso. A commercial espresso machine displayed in a coffee shop is often very ornate, with several large compartments and an elaborate plumbing scheme. Ironically, the espresso machine is often the largest piece of equipment in a coffee bar, but the actual espresso drink is served in the smallest cup, called a demitasse.
A professional espresso machine may be hooked up directly to the shop's water supply or a reservoir of hot water may be created through carefully adjusted heating elements. The water used for making espresso should be held just below the boiling point(212 degrees F or 100 degrees C). Boiling hot water will only create coffee soup, not a delicious beverage.
The barista (professional coffee maker) will use a 'burr grinder' to turn roasted coffee beans into the ideal grounds for espresso. The grinder and bean storage unit may also be located on the espresso machine itself. Once the barista has enough ground coffee beans for a single serving of espresso, the process moves to a small mesh basket with a handle. The ground coffee is placed in this basket and the barista uses a 'tamper' to compress it to a proper density.
The packed mesh basket will then be locked into position under the hot water supply line of the espresso machine. Traditional espresso machine technology employs a mechanical pump which the barista depresses to dispense the hot water. Modern espresso machines often replace this pump with automatic pistons which force water through the basket. The hot water should take 25-30 seconds to flow completely through the basket of packed coffee. A trained barista can develop a feel for the proper timing of an 'espresso shot'.
The hot water strips away most of the essential oils and flavors of the ground coffee beans as it passes through the basket and into the demitasse. The result is a very concentrated form of hot coffee--surprisingly, containing only half the caffeine of brewed coffee. The speed of the water flowing through the espresso machine does not allow all of the caffeine to be released. Espresso is usually enjoyed black, but steamed milk may be added to create cappuccinos or other specialty drinks. One of the things a barista looks for in a good espresso shot is the formation of a golden brown layer called the crema. If he or she sees this layer of concentrated coffee oils form a pool on the surface of the espresso, he or she knows that the espresso machine is working perfectly.
A home espresso machine may not be quite as elaborate as its professional cousin, but many coffee enthusiasts enjoy making espresso and other specialized beverages themselves. Flavored syrups can be purchased at coffee shops or grocery stores, and practically any brand of roasted coffee beans can be ground to espresso size in minutes. For best espresso results, the beans should only be ground just before adding them to the mesh basket for brewing. Gourmet roast coffee beans have a shelf life similar to bread, so only purchase what you'll need for a few days. When it comes to espresso, the darker and richer the bean the better.