This week, the ever-amazing Krave Coffee was asking about the changes in our decaf offerings, so figured I could pose a more general question: what is the difference in decaf processing methods?
A preamble: “death before decaf” is bunk. To crib from the offer sheet, loving coffee and loving caffeine are different. The joy I derive from coffee flows from the terroir of seed, the magic of brewing, and the wonderful communities that form around the cup. Of course, I am hopelessly addicted to caffeine but that does not mean that decaf lacks the ability to tell the same interesting seed-to-cup stories as its caffeine-laced counterparts.
Types of Decaf
There are four core methods for decaffeinating coffee. On one side, there are two solvent-based processes: direct and indirect. On the other side, there are two non-solvent processes: Swiss/Mountain Water and carbon dioxide. Regardless of approach, the first step is to take regular coffee and steam or soak coffee beans with hot water in order to increase surface area and solubility. All of the above techniques then remove the caffeine content and, following drying, we roast the beans as per usual.
Several solvents selectively dissolve caffeine. The direct and indirect designations refer to the addition of solvents to the beans or to the water extracted from the beans. Ludwig Roselius pioneered the approach in the early 1900s using benzene. There has been several alarmingly toxic variations on the carcinogenic benzene, including trichloroethylene and chloroform. While these might be great for metal degreasing or dry cleaning, today the majority of solvent-based deaf uses the organic compound methylene chloride, while a smaller segment of the decaf market uses ethyl acetate.
There are methods to manufacture the later but it also occurs naturally in many fruits and in sugar cane. Following the elimination of caffeine, steam evaporates the solvents (the boiling point of methylene chloride is 104 and ethyl acetate is 171) and the resulting beans contain a traceable reside of one part per million.
Water based methods start by soaking large numbers of beans to extract their soluble components. The beans are discarded and the liquid passes through a series of carbon filters to remove the caffeine. The resulting “green coffee extract”, as the Swiss Water company calls it, goes into a tank with a new set of beans. The extract creates equilibrium with all of the compounds in the green with the sole exception of caffeine. Thus, it migrates out and carbon filters remove it. This process is repeated until it reaches the target content window. Osmosis, pretty neat. You might asking, is the water Swiss? The process is Swiss but today all Swiss Water processing occurs at a facility in Vancouver. While all Mountain Water processing occurs at several plants in Mexico.
The final non-solvent process is carbon dioxide processing. Applying intense pressure to green coffee, water, and carbon dioxide leads to bonds between caffeine and the carbon dioxide. Because compression turns carbon dioxide to liquid, when force releases, it returns to a gaseous state and discharges the caffeine into the water for easy removal.
Cut’s Decaf Program
The decaf that I source follows the same seasonal logic as our filter program, hence its changes four to six time yearly. All of the methods above impact the taste (in particular ways) and I gravitate towards ethyl acetate (when derived from natural sources like sugarcane or fruit) for the best representation of pre-processing flavour. Water based decaf often exaggerates sour notes and undercuts fruit sweetness. While non-natural solvent based decaf frequently presents medicinal notes in the cup.Environmentally, ethyl acetate has the advantage of breathing new life into spent sugarcane and fruit, while avoiding the ‘green coffee extract’ requirement for massive quantities of water.
Carbon dioxide holds a lot of promise because, while the initial investment is large, it is very low impact and only produces reusable byproducts. It is also far less centralized opening the door to smaller farms. One of my concerns is the perception on a bag. Swiss Water is a private company with a very marketable name, while carbon dioxide (and ethyl acetate for that matter) sounds like a Frankenstein inspired mixture of plastics and contagions. The key becomes passing this information from roaster to café to customer: “I swear it’s not poison”.
tl;dr There are 4 ways to decaffeinate coffee. Our decaf sourcing follows the same mandate as our other coffees: farms and coops with strong environmental and social policies who produce delicious and interesting beans. We alternate methods and regions to find coffees that represent origin well. Decaf can be delicious.