What is Mountain Water Process decaf?
The Mountain Water Process (MWP) is a water-based decaffeination method using pure spring water from Mexican glaciers (Sierra Madre Oriental (Pico de Orizaba)), without chemical solvents. Developed and operated exclusively by Mexican company Descamex, it works on the same osmotic principle as the Swiss Water Process, with the distinguishing feature of using high-purity, low-mineral water as the decaffeination agent.
The Mountain Water Process was born in Mexico and is operated by Descamex (Descafeinadores Mexicanos, S.A. de C.V.), a company founded in 1980 by Domingo Muguira in Córdoba, Veracruz (the first decaffeination plant in Latin America; water-based process patented in 1987). The Córdoba region is one of Mexico's most important coffee growing and processing zones, which naturally led to the development of a decaffeination industry there.
The MWP process is fundamentally similar to the Swiss Water Process in its logic, but with some implementation differences. First, the water used comes from glacial sources in the Mexican Sierra Madre Oriental (Pico de Orizaba), renowned for their purity and very low dissolved mineral content (oligomineral water). Descamex presents this purity as an advantage in avoiding unwanted interactions between water minerals and coffee compounds.
As in the SWP, the process relies on creating a Green Coffee Extract (GCE) saturated with aromatic compounds but stripped of caffeine, then immersing lots to be decaffeinated in this extract. Caffeine migrates out of the beans by osmotic diffusion over 8 to 12 hours, while aromatic compounds remain in the bean due to concentration equilibrium.
A notable difference from the SWP is the specific geographic origin — the MWP is often presented as a 'Mexican terroir' product, which resonates well with the origin and traceability values of specialty coffee. Descamex also offers organic certification for its MWP lots, making them compatible with organic decaf coffees.
MWP is less universally known than SWP, but it is appreciated by some roasters seeking an equivalent-quality alternative with different origin traceability. For the end consumer, the organoleptic difference between an SWP and an MWP coffee from comparable origins is generally imperceptible — both preserve the main aromatics of the base coffee well.
In practice, the reputation of a quality MWP or SWP decaf rests above all on the quality of the green coffee chosen for decaffeination, and on the freshness of the roasting.
Swiss Water Process vs Mountain Water Process
| Criterion | Swiss Water Process | Mountain Water Process |
|---|---|---|
| Operator | Swiss Water Decaffeinated Coffee Co. (Canada) | Descamex (Mexico, Veracruz) |
| Water used | Standard filtered water | Sierra Madre glacial water (oligomineral) |
| Chemical solvent | None | None |
| Organic certification | Yes | Yes |
| Caffeine elimination | 99.9% | 99.9% |
| Process duration | 8-10 hours | 8-12 hours |
| Market recognition | Very high, global standard | High, specialty niche |
How the Mountain Water Process compares to Swiss Water
The Mountain Water Process (MWP), operated by Descamex in Mexico using water from Pico de Orizaba glacier, uses a proprietary Green Coffee Extract that is functionally similar to Swiss Water Process's GCE — a solution saturated with all coffee compounds except caffeine, which creates an osmotic environment where caffeine migrates out of the beans into the extract while other compounds remain in equilibrium within the bean. The key technical difference between MWP and Swiss Water Process is the source water: MWP uses high-altitude glacial melt water whose specific mineral profile is part of Descamex's proprietary process claim. The practical flavour difference between MWP and SWP decafs is small and difficult to reliably detect in blind tasting.
The commercial positioning of Mountain Water Process capitalises on the 'mountain water' narrative — it is a more evocative story than 'Green Coffee Extract osmosis process,' which Swiss Water Process has branded but which doesn't carry the same consumer-facing appeal. Both processes achieve similar caffeine reduction rates (97–99.9% caffeine removal), both avoid chemical solvent residues, and both preserve more of the green coffee's original flavour compound profile than methylene chloride or ethyl acetate extraction. For coffee roasters choosing between the two for specialty decaf offerings, the decision is typically based on relationship and logistics (which of the two facilities is easier to work with for their specific green coffee) rather than cup quality differences.
Going deeper
The quality ceiling of MWP decaf, like SWP, is ultimately determined by the quality of the green coffee submitted for processing. A commodity-grade green coffee processed through Mountain Water Process produces a better-than-commodity-solvent-decaf but still a mediocre cup. A specialty-grade Colombian natural with documented provenance, processed through MWP, can produce a decaf that surprises specialty drinkers. The process preserves quality potential; the green coffee provides or limits that potential. This principle — that decaffeination process quality matters but green coffee quality matters more — is the most important practical guidance for consumers evaluating decaf quality claims.