Moka pot

The moka pot[1] is a stove-top or electric coffee maker that brews coffee by passing hot water driven by vapor pressure through ground coffee. Named after the Yemeni city of Mocha, it was invented by Italian engineer Luigi Di Ponti in 1933 [2][3][4] who sold the patent to Alfonso Bialetti, an aluminum vendor. It quickly became one of the staples of Italian culture. Bialetti Industries continues to produce the original model under the trade name "Moka Express".

Not to be confused with Coffee percolator.
Moka pot
ManufacturerBialetti
Release date1933

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 including the Wolfsonian-FIU, the Cooper–Hewitt, National Design Museum, the Design Museum,[5] the London Science Museum, The Smithsonian and the Museum of Modern Art.[6] Moka pots come in different sizes, making from one to eighteen 50 ml (2 imp fl oz; 2 US fl oz) servings.[7] The original design and many current models are made from aluminium with Bakelite handles.

After the Second World War, the Italian moka pot spread all over the south of Europe and became the standard way of domestically making coffee. Its popularity led to non-Italian south European manufacturers making copies or new designs inspired by the original Italian design.

In Australia, the moka pot was traditionally used by Italian migrants who arrived mostly after the Second World War. By 2000 the moka had become popular in the homes of many Australians. Today it is quite popular at breakfast time; often Australians will add the brew to a mug and top up with either water off the boil or warmed milk.

Moka pots are typically made of aluminium, though they are sometimes made out of stainless steel or other alloys. Some designs feature an upper half made of heat-resistant glass.

Use
The bottom chamber (A) contains water. When heated, steam pressure pushes the water through a basket containing ground coffee (B) into the collecting chamber (C).
How the moka pot works

Moka pots are used over a flame or electric range. Stainless steel pots, but not aluminium, can be used with induction cooking.

A number of physics papers were written between 2001 and 2009 utilizing the ideal gas and Darcy’s laws to explain the moka pot’s brewing process, Which relies on vapor pressure created by heating water to drive it through the coffee grounds, and thence brewed coffee into the upper chamber.[8]

A rubber gasket ensures a tight seal between components, and a safety valve prevents over-pressurization.

Preparation

The boiler (marked A in the diagram) is filled with water to an etched line (or slightly below the safety release valve). While at-home makers generally do not preheat the water used, it can expedite the brewing process in commercial settings.[9] The metal filter funnel (B) is inserted. Finely ground coffee is added to the filter as shown. How tightly the coffee is packed impacts how quickly the coffee extracts[10] and the strength of the brew. The pot is then heated, so that the water boils.

Brewing

The heating of the boiler, A, leads to a gradual increase of the pressure due to both the expansion of the enclosed air and the raised vapor pressure of the increasingly heated water. When pressure becomes high enough to force the water up the funnel through the coffee grinds, coffee will begin to pour into the upper chamber (C).

When the lower chamber is almost empty, bubbles of steam mix with the upstreaming water, producing a characteristic gurgling noise - a signal that brewing should be stopped. Navarini et al. call this the "strombolian" phase of brewing, which allows a mixture of highly heated steam and water to pass through the coffee, which leads to rapid overextraction and introduction of undesirable flavors.[10]

Funnel with ground coffee
Mid-brew
Layer of crema developing

Maintenance

Moka pots require periodic replacement of the rubber seal, a scouring of its removable filter, and a check that the safety release valve is not blocked. All parts of the pot should be scrubbed by hand using a mild detergent, as aluminium moka pots are not dishwasher safe.[11][12][13]

Aluminum migration

The potential for toxic amounts of aluminium migration being created by brewing an acidic beverage in an aluminium pot have been scientifically investigated, and determined to be "negligible" - falling below 1% of recommended total weekly intake level once a new pot has been used.[14] Following the pot's stabilization at below 1% with regular use, migration rose to a maximum observed level of just under 4% after a dishwasher cleaning, resulting in dishwasher use being strongly discouraged.

Pot sizes

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.

Bialetti "Moka Express"
Espresso
cups		 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
6 300 216 102 10 8+1⁄2 4
9 550 254 105 18+1⁄2 10 4+1⁄8
12 775 292 127 25 11+1⁄2 5

Moka coffee characteristics

All brewed coffee flavor depends greatly on bean variety, roast level, fineness of grind, water profile, and the level of heat used. The Moka pot is no different.

Moka pots are sometimes referred to as stove-top espresso makers. However, a typical moka coffee is extracted at relatively low pressures of 1 to 2 bar (100 to 200 kPa),[10] 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.[15][16]

Variations and brands

Several models of Bialetti moka pot
Moka 2 Cup Coffee Fountain[17]

Among the variations to the moka pot design that have been introduced are those to expedite brew time, create milk froth, and allow microwave brewing.

To expedite brewing, a weighted valve called Cremator or Cremavent has been added as a pressure regulator on top of the nozzle that allows pressure to build up inside the water tank in a manner similar to a pressure cooker. As pressure builds up more quickly in this method (since there is much less leakage of vapour) compared to the standard moka pot, it reaches the level required for water to rise through the ground coffee in a shorter time. The result is coffee brewed at a higher pressure and temperature than the standard pot, making it more similar to espresso and therefore with more visible crema.

Another variation allows for milk to be frothed and mixed with the coffee during brewing.[18]

Some variants made of plastic instead of metal can be used in microwave ovens.

See also

Notes
  2. "Italy's coffee pot king was buried in the appliance that made him famous". qz.com. Retrieved 14 May 2023.
  3. "Bialetti Technical Description". fmartinezport.commons.gc.cuny.edu. Retrieved 14 May 2023.
  4. "Who Made That Moka Express". The New York Times. Retrieved 14 May 2023.
  5. Greenbaum, Hilary (1 September 2011). "Who Made That Moka Express?". The 6th Floor Blog.
  6. Wilson, Mark (9 April 2019). "The world's most famous coffee pot gets a redesign". Fast Company. Retrieved 10 October 2022.
  7. "Moka Express factsheet" (PDF). Bialetti. Archived from the original (PDF) on 14 December 2010. Retrieved 1 March 2009.
  9. Hoffmann, James (2020). The World Atlas of Coffee. Firefly Books. p. 91. ISBN 978-0-2281-0094-2.Stephenson, Tristan (2019). The Curious Barista's Guide to Coffee. New York: Ryland Peters & Small. p. 132. ISBN 978-1-78879-083-3.
  10. Navarini, L.; Nobile, E.; Pinto, F.; Scheri, A.; Suggi-Liverani, F. (April 2009). "Experimental investigation of steam pressure coffee extraction in a stove-top coffee maker" (PDF). Applied Thermal Engineering. 29 (5–6): 998–1004. doi:10.1016/j.applthermaleng.2008.05.014. S2CID 110656959.
  11. "Tips and Care". bialetti.co.nz
  12. "How to Clean a Moka Pot". thekitchn.com Running the pot through the dishwasher generally results in corrosion and oxidation of the protective oxidized layer of aluminium, leaving freshly exposed aluminium to react with the air, creating a dirty, reactive, and blackened surface.
  13. Stahl, Thorsten; et al. (12 April 2017). "Migration of aluminum from food contact materials to food—a health risk for consumers?". Environmental Sciences Europe. 29 (18): 18. doi:10.1186/s12302-017-0118-9. PMC 5388725. PMID 28458988. While not producing unsafe levels, brewing with the pot after dishwasher usage results in a larger aluminium content leaching into the coffee.
  14. Stahl, Thorsten; et al. (12 April 2017). "Migration of aluminum from food contact materials to food—a health risk for consumers?". Environmental Sciences Europe. 29 (18): 18. doi:10.1186/s12302-017-0118-9. PMC 5388725. PMID 28458988. [H]uman inner aluminum exposure through the proper use of aluminum moka pots is negligible. Even under the worst-case scenario of washing the moka pots in a dishwasher, the uptake amounts to only 4% of TWI. The manufacturers expressly warn not to clean the aluminum moka pots in the dishwasher. Summary: An initially low level of aluminium migration (of under 3% recommended total weekly intake (TWI)) occurs after the very first use of a new pot, after which the level stabilizes below 1% TWI, decreasing with each observed use; migration after dishwasher cleaning increases to a maximum observed level of just under 4%, and thus dishwasher cleaning is strongly discouraged.
  15. "Espresso Italiano Certificato" (PDF). Istituto Nazionale Espresso Italiano. Archived from the original (PDF) on 26 July 2011. Retrieved 30 January 2011.
  16. "Espresso and classic drink Wiki". Archived from the original on 7 July 2011. Retrieved 30 January 2011.
  17. "Fontanella Argento per una tazzina". Sant'Eustachio il Caffè (in Italian). Retrieved 22 June 2023.
  18. How to Use the Bialetti Mukka Express, retrieved 27 February 2023 youtube

References
  • Rombauer, Irma S.; Marion Rombauer Becker; Ethan Becker (August 1997). The Joy of Cooking. Scribner. pp. 28–29. ISBN 0-684-81870-1.
  • Schnapp, Jeffrey T. (2004). "The Romance of Aluminum and Caffeine". In Brown, Bill (ed.). Things. Chicago: University of Chicago Press. pp. 209–239.

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