The moka pot is a stove-top or electric coffee maker that brews coffee by passing boiling water pressurized by steam through ground coffee. Named after the Yemeni city of Mocha, it was invented by an Italian engineer named Alfonso Bialetti in 1933 and quickly became one of the staples of Italian culture. Bialetti Industries continues to produce the same model under the name "Moka Express".
Spreading from Italy, the moka pot is today most commonly used in Europe and in Latin America. It has become an iconic design, displayed in modern industrial art and design museums such as the Wolfsonian-FIU, Museum of Modern Art, the Cooper–Hewitt, National Design Museum, the Design Museum, and the London Science Museum. Moka pots come in different sizes, from one to eighteen 50 ml (2 imp fl oz; 2 US fl oz) servings. The original design and many current models are made from aluminium with Bakelite handles.
Brewing coffee with a moka pot
The boiler (marked A in the diagram) is filled with water almost up to the safety release valve (some models have an etched water level sign) and the funnel-shaped metal filter (B) is inserted. Finely-ground coffee is added to the filter as shown below. Then the upper part (C, which has a second metal filter at the bottom) is tightly screwed onto the base. The pot is placed on a suitable heat source, the water is brought to its boiling point, and thereby steam is created in the boiler.
A gasket ensures a tightly closed unit and allows for pressure to safely build up in the lower section, where a safety valve provides a necessary release in case this pressure should get too high (with clean filters, that should not happen).
The steam eventually reaches a high enough pressure to gradually force the surrounding boiling water up the funnel through the coffee powder and into the upper chamber (C), where the coffee is collected. Although the "boiler" on a moka pot contains steam at elevated temperature and pressure, the water forced up through the grounds is no hotter than that used in other brewing methods – up to 90 °C, depending on the stage of extraction.
When the lower chamber is almost empty, bubbles of steam mix with the upstreaming water, producing a characteristic gurgling noise. This "strombolian phase" allows a mixture of steam and water to pass through the coffee, which leads to undesirable results, and therefore brewing should be stopped by removing the pot from the stove as soon as this stage is reached.
Moka pots require periodic replacement of the rubber seal and the filters, and a check that the safety release valve is not blocked. When the rubber seal is new, it might alter the coffee taste, so a couple of "dry runs" can be made, without coffee or with used coffee grounds to "prime" it.
Moka pot dimensions
The moka pot comes in various sizes based on the number of 50 ml (2 imp fl oz; 2 US fl oz) espresso cups they produce. The following table are the standard sizes for the Bialetti Moka Express.
|Metric units||US units|
|Volume (ml)||height (mm)||base (mm)||Volume (US fl oz)||height (in)||base (in)|
|1||60||133||64||2||5 1⁄4||2 1⁄2|
|3||200||159||83||6 1⁄2||6 1⁄4||3 1⁄4|
|9||550||254||105||18 1⁄2||10||4 1⁄8|
Moka coffee characteristics
The flavor of moka pot coffee depends greatly on bean variety, roast level, fineness of grind, water profile, and the level of heat used.
However, a typical moka coffee is extracted at relatively low pressures of 1 to 2 bar (100 to 200 kPa), while standards for espresso coffee specify a pressure of 9 bar (900 kPa). Therefore, moka coffee is not considered to be an espresso and has different flavor characteristics.
Additionally, some moka pots have a special valve which allows producing more crema.
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- Schnapp, Jeffrey T. (2004). "The Romance of Aluminum and Caffeine". In Brown, Bill (ed.). Things. Chicago: University of Chicago Press. pp. 209–239.
Media related to Moka pot at Wikimedia Commons