Decaf specialty coffee - is there such a thing?

In a word: YES. In more words: Yes but it's not usually the best. Decaffeinated coffee is a small and important part of the specialty coffee scene, and can be done well. However, because all the methods of decaffeination have some impact on flavour, it's never the best coffee you can get. If you want good decaf, choose a good supplier, a good bean, and most importantly: a good decaffeination process that you can trust.

Most roasters or bean suppliers offer one or more decaf varieties (here are some from Heart, Intelligentsia and Seven Seeds), although the variety is rarely large (for a number of reasons including lower demand and thus limited supply, processing costs, the difficulty of preserving/accentuating flavour with processing and all the associated brand risk). All specialty roasters mention the decaffeination process. It's usually either 'swiss water', 'mountain water' or some acronym. There are a number of different methods, it's worthwhile understanding them.

 Coffee before and after decaffeination

Coffee before and after decaffeination

Summary: Which decaffeination method is best?

If your coffee has the decaffeination process on the bag, prefer these types of decaffeination:

  • Mountain water/Mexican mountain water: Using no chemicals, this method reliably extracts 99.9% of all caffeine and leaves delicious tasting coffee
  • Swiss water: Also using no chemicals, this is a reliable decaffeination process, also reducing 99.9% of caffeine, that just doesn't produce as flavourful coffee.
  • "Natural" process or chemical process: This uses either naturally occurring (but synthetically made) or synthetic solvents, and only buy this process if you really trust the whole supply chain to adhere to standards of quality. If you do, this can be the best tasting decaf with ~97% of caffeine removed! If you don't know, then stay away.
  • If no decaffeination process is mentioned: a direct chemical method was probably used and you should stay away until you learn more.

In the coffee industry overall (including decaf and supermarket beans), chemical methods are prevalent (most supermarket instant decaf is produced using the direct chemical method, using methylene chloride). However, in specialty coffee, water processes are more common, with names like 'Swiss water' or 'Mountain water' methods often touted. Let's examine these one by one.

Chemical methods

Chemical methods are used with two principal types of solvents: methylene chloride and ethyl acetate, and two chemical methods: direct and indirect decaffeination. You can understand it in summarised form using the table below.

Decaf guide table

In summary, chemical methods have these pros and cons:

  • Pros: Removes ~97% of all caffeine. Can taste better if done correctly. Has no known health risks if prepared correctly.
  • Cons: Chemicals! If not prepared correctly, can taste bad or be dangerous, and there may be unknown health risks anyway. If not done rigorously, caffeine can be eliminate by only ~85-90%.

Chemical solvents used

There are three chemicals used commonly in deccafeination: methylene chloride (a.k.a. dicloromthane)ethyl acetate and pressurised carbon dioxide

Methylene Chloride

This is a synthetic solvent. When it makes contacts with caffeine it bonds with it and it can be then separately naturally from the coffee using filters. 'Solvents' in large or undiluted quantities are dangerous chemical, but in small quantities they are harmless. The USFDA describes quantities of less than 10ppm in coffee to pose a 'non-existent' health risk. The EU is stricter, with a 3ppm standard. The chemical is highly volatile and is completely destroyed at the temperature used to brew coffee (and before then, in roasting). Coffee prepared using methylene chloride, if prepared correctly, consistently tests below 1ppm, and therefore poses no known health risks.

Nonetheless, it is a dangerous chemical, and must be handled appropriately. Sweet Maria's only occasionally offers decafs when they are processed in Germany, where they can be confident that it has been done so according to guidelines. If a specialty coffee is prepared using this method, only buy it from a supply chain you can trust. 

Ethyl acetate

This chemical is a similarly effective and volatile solvent that occurs naturally in ripening fruit. Apart from decaffeinating coffee, it is commonly used in glues, nail polish removers (different to acetone) and cigarettes. For this reason, Ethyl acetate processed coffee is sometimes called naturally processed decaf for marketing purposes. However, it is so hard to extract ethyl acetate naturally that it is often produced synthetically, so effectively there is no difference. It bears similar risks and only a small quantity should ever be present in coffee for it to be safe. 

Pressurised carbon dioxide (CO2)

Plain old CO2... an interesting solvent. At very high pressures (250-300x atmospheric pressure), carbon dioxide (a naturally occurring gas in vast quantities in our atmosphere) takes on liquid-like properties and becomes a solvent as effective as the others. Once the carbon dioxide bonds with the caffeine, it is passed through a bed of charcoal to filter out the caffeine before the gas/liquid is re-introduced to the coffee. Using a naturally occurring and low toxicity gas is obviously attractive. However the main difficulty with the usage of this solvent is the capital intensivity of setting up high pressure chambers.

Chemical methods used

There are two main methods of decaffeination - the indirect method and the direct method.

The indirect method

This is currently the favourite chemical process used - when a chemical process is used at all. First the beans are soaked in hot water, separating the caffeine. The beans are separated from the water, and methylene chloride is added to the water only. The chemical bonds with the caffeine, and then the chemical and caffeine are removed together. Finally, the beans are added back in, to re-introduce their other flavour elements that became dissolved in the water.

Before you start thinking 'warning! chemicals!' it's useful referring to Sweet Maria's defense of this method. Essentially they say: 

  1. This tastes the best! Coffee cuppers consistently rate this method as producing the best tasting decaf. 
  2. The coffee tests consistently at only 1PPM of methylene chloride - lower than the EU's guidelines of 3PPM and the USDA's 10PPM standard allowances. 
  3. Methylene chloride completely dissipates at the temperatures used to brew coffee (and before that, roasting it).

In summary: specialty coffee can be done well using the indirect chemical method, but mostly exercise caution.

The direct method

This method involves direct exposure of coffee to chemicals. In this method, the coffee beans are first moistened either with a soak or a spray, and then a diluted solvent is applied to the beans directly. After the solvent bonds with the caffeine, the liquid is then allowed to evaporate, at which point the solvent is captured. The beans are washed in water, and then steamed to remove traces of the solvent. This process is repeated until the level of caffeine reduces to an acceptable level. Needless to say, the direct exposure of coffee to chemicals and the repeated washing has a significant negative effect on the most interesting aspects of coffee, and so this method is not (to my knowledge) at all used in specialty coffee.

Water (non-chemical) methods

As their name suggests, water methods are generally preferred in specialty coffee circles. Despite their different branding, all water methods are fundamentally the same: Chemical free and somewhat impactful on flavour. Water methods can be summarised as

  • Pros: Removes ~99.9% of all caffeine. Does not use chemicals.
  • Cons: Can be detrimental to the flavour.

Swiss water method

This method is very frequently used in specialty coffee, and is commercially implemented by the Swiss Watter Decaffeinated Coffee Company in Canada. The process is:

  1. The coffee is immersed in hot water to dissolve and extract the caffeine. In the process, oil and flavour compounds are also extracted through osmosis (like brewing whole-bean coffee), leaving the beans flavourless. These beans are discarded. 
  2. The water is then passed through an activated carbon filter, designed to capture only the larger caffeine molecules, while allowing oil and flavour molecules to pass through. 
  3. A fresh batch of beans is now immersed in the water that is rich with flavour and oil compounds. This time, due to the presence of flavour and oil compounds in the water, these are not extracted from the beans - only caffeine is. The beans are removed and the process is repeated until the beans are almost cafeine free by mass.

This is a very effective method for decaffeination that does not entirely corrupt the flavour. However, you can naturally assume that immersing coffee in vats of water will always affect the flavour to some degree. Further, it is an expensive process - the same water cannot be reused too many times, and so the process necessarily means discarding a large amount of beans.

Mountain water method

This process, also known as "Mexican mountain water", is a process commercialised by a company in Mexico called Sanroke. The water is from the glaciers in Mexico, and is identical to the Swiss Water process except that a) it is performed by a different company and b) the process delivers (reportedly) better tasting cups. Sweet Marias prefers this water process to Swiss Water.