What is Espresso Coffee:
Espresso or caffè espresso is a concentrated coffee beverage
brewed by forcing very hot, but not boiling, water under high
pressure through coffee that has been ground to a consistency
that is between extremely fine and powder. Invented by Edward
Loysel de Santais in 1843, Santais's machine impressed visitors
to the Paris Exposition of 1855 by producing "two thousand cups
of coffee an hour." Santais's machine brewed coffee a pot at a
time; however, and used steam pressure, though not to force the
brewing water directly through the coffee. Instead, it raised
the water to a considerable height above the coffee. From there
it descended through an elaborate system of tubes to the coffee
bed. The weight of the hot water, not the trapped steam, applied
the brewing pressure.
Espresso was developed in Milan, Italy in the early 20th century,
but up until the mid-1940s it was a beverage produced solely with
steam pressure. The invention of the spring piston lever machine
and its subsequent commercial success changed espresso into the
beverage we know today. Espresso is now produced with between 9 and
10 atmospheres or bars of pressure.
The defining characteristics of espresso include a thicker consistency
than drip coffee, a higher amount of dissolved solids than drip coffee
per relative volume, and a serving size that is usually measured in shots,
which is about 30ml (1 ounces) in size. Espresso is chemically complex and
volatile, with many of its chemical components quickly degrading from
oxidation or loss of temperature. Properly brewed espresso has three major
parts: the heart, body, and the most distinguishing factor, the presence of
crema, a reddish-brown foam that floats on the surface of the espresso.
It is composed of vegetable oils, proteins and sugars. Crema has elements
of both emulsion and foam colloid.
As a result of the high-pressure brewing process, all of the flavors and
chemicals in a typical cup of coffee are concentrated. Because of its
intense and high concentration of ingredients (including caffeine), espresso
lends itself to mixing into other coffee based drinks, such as lattes,
cappuccini, macchiati and mochas, without being diluted in the resulting drink.
Espresso contains approximately twice the caffeine content per volume as
regular brewed coffee, at approximately 40 milligrams per fluid ounce, but
only about 1/3 the content per serving.
Brewing Espresso Coffee:
Preparation of espresso requires an espresso machine, as it is the process that
makes espresso the beverage that it is. The act of producing a shot of espresso
is termed "pulling" a shot. The term derives from lever espresso machines, which
require pulling down a handle attached to a spring-loaded piston, forcing hot water
through the coffee at the requisite pressure. To pull a shot of espresso, a metal
filter-basket is filled with 7 to 10 grams of ground coffee for a single shot or
12 to 18 grams for a double shot. The espresso is then tamped into a firm puck of
coffee. The portafilter (or group handle) holds the filter-basket and is locked under
the grouphead's diffusion block. When the brew process begins, pressurized water at
90±5 °C (200±9 °F) and approximately 900 kPa (130 PSI) is forced into the grouphead
and through the ground coffee in the portafilter. Water cooler than the ideal zone
causes sourness; hotter than the ideal zone causes bitterness. High-quality espresso
machines control the temperature of the brew water within a few degrees of the ideal.
The serving temperature of espresso is significantly lower, typically around 60-70 °C,
owing to the small serving size and the cooling effects of the cup and the pouring
This process produces a rich, almost syrupy beverage by extracting and emulsifying
the oils in the ground coffee. An ideal shot of espresso should take between 17 and
26 seconds to arrive on a professional-grade machine (optimum at 22 seconds), timed
from when the machine's pump is first turned on (unless the machine has a "preinfusion"
stage, which may add about 7 seconds to the process). Varying the fineness of the grind,
the amount of pressure used to tamp the grinds, or the pump pressure itself can be used
to bring the extraction time into this ideal zone. Most prefer to pull espresso shots
directly right into a pre-heated demitasse or shot glass, to maintain the ideal temperature
of the espresso and preserve all of its crema. Apart from the espresso made manually by a
barista, most espresso is made by automatic machines in which the brewing process takes
place with an espresso-brewer.
Freshly brewed espresso must be served or mixed into other coffee beverages immediately,
or it will begin to degrade due to cooling and oxidation. Temperature and time of consumption
are important variables that must be observed to enjoy an ideal espresso; it should be
consumed within 2 minutes from when it is served.
A recent North American brewing trend came with the introduction of the bottomless portafilter,
that is, a portafilter without the bottom half, exposing the basket and causing the espresso
to bypass contact with the portafilter during extraction. The bottomless portafilter serves as
a tool to analyze evenness of grind distribution and tamping, as a greater volume of espresso
will flow from low-density areas of the coffee puck. Some prefer the taste, citing the
portafilter's capacity to preserve crema. Crema is also known as Schuma in South America.