Decaf? Meh, say most coffee drinkers. We want the caffeine buzz as well as the coffee flavour.
The most well-known decaf method is Swiss Water Process, a proprietary thing done by a company based in British Columbia. A batch of green beans is soaked in hot water, dissolving the caffeine and most of the flavour compounds and oils. These beans are discarded, and the caffeine-and flavour-saturated water is passed through a charcoal filter to remove the caffeine. Then a fresh batch of beans is soaked in the flavour-saturated water: caffeine is leached out, but not (so much) flavour.
Padre in Melbourne sources its decaf from Swiss Water: it's a Sumatra Mandheling that makes a short black with a bright front and a bittersweet finish, though the overall flavour and mouthfeel is a bit flat and lacking in sparkle. In a piccolo the sweetness of the milk rounds things out: it might almost pass for regular milk coffee if you didn't know.
Single Origin Roasters in Sydney also use green beans from Swiss Water, while Five Senses sources its Colombian Medellin Excelso decaf from Mountain Water, a company based in Mexico that uses a similar water-based decaffeination method.
Then there are the solvent-based methods. Seven Seeds in Melbourne offers a Colombian single origin that is decaffeinated using ethyl acetate, a solvent obtained by fermenting sugar cane. (Ethyl acetate - natural or synthesised - is also used as a flavouring in food, and in nail polish remover and some paint.)
The beans are steamed to make them more porous, then washed with the ethyl acetate, which leaches away the caffeine.
In a short black, the Seven Seeds Colombian decaf has a bright front like a typical Seeds espresso, and a lingering fruity bitter-sweetness that may partly be due to the ethyl acetate (present in less than 30 parts per million, says the Colombian processor, Descafecol). It's also a little flat-tasting compared with regular coffee, as if the flavour complexity had been ironed out - a decaf hallmark, it seems.
The No. 1 cafe crime with decaf, says Ben Bicknell from Five Senses, is using pre-ground coffee: if you want decent decaf, look for a dedicated decaf grinder, which indicates the cafe is at least using whole (hopefully fresh) beans.
The same goes for decaf at home: buy whole beans, from a reputable small roaster (you can do it online at padrecoffee.com.au, singleorigin.com.au, fivesenses.com.au and sevenseeds.com.au, among others), in small quantities - and grind as you go.