What makes a specialty coffee taste good? The science behind your morning cuppa

How was your morning cup of washed Or did you go for the natural bourbon to start your day?

Confused? You're not alone. The world of specialty coffee is peppered with terms like "honey-processed", "funky notes" and "first crack".

But what do they mean — especially for the taste and aroma of your morning coffee?

Only recently has the coffee industry described their products in such depth, according to Melbourne roasting consultant Anne Cooper.

"The coffee industry is just starting to do what the wine industry has done forever," she says.

But before we start decoding the jargon around specialty coffee, we first need a quick lesson in coffee anatomy.

Coffee beans aren't beans
What we think of as coffee beans are actually the seeds of cherry-like coffee fruit.

Each cherry contains two seeds, which are coated by a thin parchment membrane and enveloped by a sticky, sweet layer called mucilage.

Only the best coffee, judged by professionals called Q graders, is deemed "specialty", Jonathan Parkes, quality control and training manager at Dimattina Coffee in Perth, says.
Nearly all specialty coffee comes from the Coffea arabica species.

Within this species are different types — including catuai, bourbon, gesha, catimor — all of which impart different flavours to their seeds.

The climate, soil, terrain and altitude where a coffee crop is grown can also affect taste.

Trees high in the mountains have slow-growing fruit, for instance, and tend to produce complex fruity, floral coffee, while faster-growing, low-altitude coffees are less acidic and taste earthier.

When they're ready for picking, coffee cherries turn typically deep red, but this can vary depending on the type. Bourbon coffee cherries, for instance, are ready when they're bright yellow.

To get to the seeds within, coffee cherries are processed, often at the farm they were grown.

What's up with washed, natural and honey processing?
Most specialty coffee on the market is washed.

"Once the cherry is picked, a de-pulping machine strips all the flesh off, leaving the seeds still in their mucilage coat," Mr Parkes says.

The seeds are then soaked in big vats for a day or more. This has two jobs: to soak off the mucilage and to start fermentation.

Fermentation, Mr Parkes says, can produce sweetness in the coffee.

"But the key is to not over-ferment. If you have too much, you'll end up with acetic acid, or vinegar," he says.

Then the seeds are run through troughs to scrub the sticky mucilage off, and laid on patios or raised beds to dry.

Depending on the weather, drying can take a week or so.

"You want to get a 10 to 13 per cent moisture content in the seed before it's packaged and sent off to a dry mill," Mr Parkes says.

A dry mill removes the last remaining bits of mucilage and parchment membrane from the coffee seeds before they're packaged up and sold.

Because washed coffees need loads of water, drier producing areas, such as Africa, tend to produce natural coffees.

"You pick the cherries straight off the tree, and you throw them on a patio or drying bed for a couple of week — maybe a month," Mr Parkes said.
By allowing the coffee seeds to dry with the flesh and skin on, the seed, which is quite porous, absorbs sugars within the fruit.

"It gives natural sweetness to the coffee."

This process also leads to quick fermentation, so extra care has to be taken to avoid a build up of acetic acid. Strong fruity flavours that are called 'funky notes' can also develop.

"If you have a natural Ethiopian, it can taste like really pungent blueberries if you get a really funky coffee," Mr Parkes says.

"But there's a fine line between funky and defective, so it can be open to interpretation."

Once the fruit is dry, the pulp is removed and the coffee seeds are sent to the dry mill.

Then there's honey processing, which is somewhere between the technique used to produce washed and natural coffee beans.

The cherry's flesh is stripped away after it's picked, as with washed coffees, but instead of being dunked in water, the mucilage-covered seeds are dried in the sun, as with natural coffees.

"So you get some of the sugars being absorbed by the seed, but not as much as the natural process," Mr Parkes says.

Farmers can leave different amounts of mucilage on, too, he added. In black honey processing a lot of mucilage is left on, while in white honey processing not much is left on at all.