The original design and many current models are made from aluminium with Bakelite handles, 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 worksX-ray video of a moka pot in use
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, along with the temperature-dependent vapor pressure of water, to explain the moka pot's brewing process.[9]
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.[10] The metal filter funnel (B) is inserted. Finely ground coffee is added to the filter. How tightly the coffee is packed impacts how quickly the coffee extracts and the strength of the brew.[11] The collector (C) is then attached and the pot is 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.[11]
Unlike a standard percolator, the moka pot never sends brewed coffee back through the coffee grounds.
Funnel with ground coffee
Mid-brew, showing brewed coffee in the process of being transported through the funnel
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.[12][13][14]
Aluminium 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.[15] 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 approximate number of espresso-sized cups they produce, with each cup measuring 50ml (2impfloz; 2USfloz). The following table lists some sizes for Bialetti Moka pots:
Brewed coffee flavor, including that of a moka pot depends greatly on bean variety, roast level, fineness of grind, water profile, and the level of heat used.
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 2bar (100 to 200kPa),[11] while standards for espresso coffee specify a pressure of 9bar (900kPa). Therefore, moka coffee is not considered to be an espresso and has different flavor characteristics.[clarify][18][19]
Variations and brands
Several models of Bialetti moka potMoka 2 Cup Coffee Fountain
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 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. [citation needed]
Another variation allows for milk to be frothed and mixed with the coffee during brewing.[21]
↑ Greenbaum, Hilary (1 September 2011). "Who Made That Moka Express?". The 6th Floor Blog. Archived from the original on 7 August 2021. Retrieved 7 August 2021.
↑ "Tips and Care". Archived from the original on 9 October 2024. Retrieved 27 November 2020. bialetti.co.nz
↑ "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.
↑ Stahl, Thorsten; etal. (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. PMC5388725. PMID28458988. [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 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.
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