Maybe you’ve always wondered about what coffee is. Today we’re here to give you a first overview of how coffee comes to be from tree to roasted coffee beans. Read on for a short 101 on coffee processing, how it’s done and how it affects the flavors in your cup. Our focus is on Honey Processed coffees, as we’ve just released a few Honey Process coffees from El Salvador and Costa Rica, where “Honey” processing is all the rage.
First, we’ll have a look at the anatomy of a coffee cherry. And then we’ll discuss the various ways in which coffee cherries can be transformed into nicely roasted delicious coffee.
The Anatomy of a Coffee Cherry
A coffee cherry has, roughly speaking, five layers
The five layers are:
- Skin / Pulp: On the outside, the two coffee seeds are covered by a cherry-like skin. With the exception of dried-in-the-fruit or Natural Process coffee, this outer layer is removed within a few hours of harvest. In an edible cherry (like a nice plumb and sweet Rainier cherry from Eastern Washington), we might call this skin the “flesh”. In coffee, the skin is mostly considered a by-product (some make tea out of it).That’s why it’s called “pulp” and the machine to remove it is called a depulper.
- Mucilage: Beyond the skin lies the mucilage, a sticky, gluey substance surrounding each of the two seeds. Since it is so sticky and sugary, it is sometimes called Honey. (Mucilage is found in most fruit. It’s not unique to coffee: http://en.wikipedia.org/wiki/Mucilage)
- Parchment: After the mucilage, a layer of cellulose protects each of the coffee seeds. When dried, this layer looks and feels like parchment paper, hence the name.
- Silver skin / Chaff: Further inside, an even thinner layer coats the seed. This layer is called the silver skin because of its somewhat silverish sheen. This layer comes off during roasting. If you ever notice flakes in ground coffee, that is usually bits of silver skin or chaff that didn’t separate from the beans during the roast process.
- Seed / Coffee Bean: As you’ve already discovered, basically the coffee bean is one of the two seeds from inside the coffee cherry (Peaberries are an anomaly in which only one small, round seed formed inside the cherry. Usually, about five percent of all coffee is graded as a peaberry.) It is dried and infertile by time we receive it, ready to roast.
The Three Principal Processing Methods in Coffee
We know of three principal categories of processing methods. These three processes differ in the number of layers that are removed before drying. Here is the short list:
- Natural or Dried in the Fruit Process – no layers are removed.
- Honey Process – skin and pulp are removed, but some or all of the mucilage (Honey) remains.
- Washed Process – skin, pulp, and mucilage are removed using water and fermentation. Also called Fully Washed. This is the conventional form of Arabica coffee processing used in most parts of the world. It is possible to skip the fermentation step by using a high-tech pressure washing machine to remove the skin, pulp and some or all of the mucilage. This process is called Pulped Natural.
In terms of how many layers of the fruit are removed, and how much water is used, the Honey Process is about mid-way between the Natural (Dry) and Washed (Wet) Processes.
What follows are the finer points of each of these methods.
Natural or Dried-in-the-Fruit
This is the easiest method to explain: the cherry gets picked off the bush and dried more or less without further ado. This is the oldest method, and is still used in Ethiopia and Brazil and sometimes in other coffee growing areas, especially when there is no water available. Drying can take up to four weeks, and it is very tricky to ensure that no moldy or off flavors get into the beans. It only works well in very dry climates or when supplemented by mechanical drying (basically running hot air through the beans to dry them faster and in a more controlled way.)
Drying coffee in the fruit keeps many of the fruit flavors in the beans. You’ll find that coffees processed in this way are often very fruit forward tasting and brighter than other coffees. The pulp is removed mechanically after the cherries are dried (“Dry Milling”).
In this method, the skin of the coffee cherry is removed mechanically using a specialized machine, called a depulper. Then the beans are put into fermentation tanks until the mucilage is no longer sticky. The sugar in the mucilage gets broken down during the fermentation process. Depending on the fermentation method, this takes anywhere from 12 hours to six days (some farmers ferment the coffee using several rinse cycles, this is called the Kenyan method and takes several days). Determining when to end the fermentation is very important – over-fermented coffee will taste sour! Once the stickiness is used up, the remnants of the mucilage are washed off using copious amounts of water. (The huge amount of water used to wash off the mucilage is one of the worst environmental impacts of coffee production, but there are some newer innovations that decrease, recycle and filter the water used in this method.) This method was developed in the 19th century and is also called “wet processing”.
The controlled fermentation of the mucilage imparts a certain amount of acidity into the coffee which persists into the cup. However, by washing the beans right after fermentation, much of the fruit flavor and acidity is removed. What remains are the more subtle flavors of coffee alongside a good bit of acidity.
Pulped Natural is a common processing method in Brazil. Pulped Natural is similar to the Washed process except that the mucilage is removed using a pressure washing apparatus, skipping the fermentation process altogether. A couple of companies in Brazil and Colombia have had this method patented and remain the market leaders with a quasi-monopoly on this pressure washing “Robot”. The method uses much less water than the Washed Process, so it is sometimes called Semi-Dry. Since there is no fermentation, there is little risk of over/ under fermentation, thus increasing overall consistency. Unfortunately, without any fermentation, the flavor tends to be consistent but bland. For this reason, farmers do not use this method on super-premium coffee varieties, and we rarely buy coffee that is processed in this way.
Honey process is currently all the rage in Costa Rica and it has started to spread to all the other Central American countries. Remember that the mucilage of the coffee cherry is sticky and slimy, so it is sometimes called “honey”. During the Honey Process, coffee is dried with some or all of the mucilage remaining on the parchment encasing the seed. Coffee cherries are picked, sorted, depulped, and then moved to drying patios or beds for various periods of time.
Because there is a little bit of fermentation happening in the short amount of time it takes for the mucilage to dry, coffees processed in this way feature a little more acidity than Pulped Naturals (Pressure-Washed) coffees, but significantly less acidity than Washed or Natural/Dried-in-the-Fruit coffees.
Since Honey is our focus today, let’s take a brief look at some variations in honey processing and how they affect the flavor of the resulting coffee.
Degree of Honey
Farmers switching to Honey Process have to use the processing equipment they already have. Because their processing plants (Beneficios in Latin America, Factories in Kenya, Washing Stations in Ethiopia, etc.) are usually set up to transport coffee using copious amount of water, many farmers inadvertently wash off some of the mucilage just by transporting coffee in water ways from one point of their processing plant to another. Some Costa Rican coffee farms have Brazilian or Colombian “Robot” pressure washing equipment. They can use their “Robot” to wash off some or all of the mucilage. Depending how much mucilage remains — it could be 40%-100% — farmers call their coffee 40%, 60%, 80% or 100% Honey. Of course, you have to take that statement with a grain of salt. By taking off some of the Honey (mucilage), if they’re intentional about it, the farmers hope to make the beans a little less sticky and reduce any risk that fermentation can go sour during the drying process.
The Honey Color Spectrum
Recently, some Costa Rican farmers started assigning a color attribute to their Honey processed coffee: Yellow, Red, or Black. This indicates the amount of light the coffee gets exposed to during drying.
Yellow Honey is exposed to the most light. Because more light means more heat, this coffee usually takes just about a week to dry. (Drying times always depend on the general weather conditions, temperature, and humidity). Red Honey is dried for two to three weeks, usually on overcast days or in the shade. If it’s very sunny, the farm workers will cover the drying coffee for longer periods of time to reduce light exposure. Black Honey gets the most sheltered from the light and dries for the longest amount of time: at least two weeks. It’s the most labor-intensive and expensive of the honey processed coffees.
The photo, from Finca Las Lajas in Costa Rica, shows beans arrayed from fully washed through various levels of honey, all the way to natural. Fully washed dries the fastest and tastes the cleanest. Natural takes the longest time to dry and could have the most fruit forward flavor. Lighter honeys are dried faster than the darker ones. The longer dry time will probably tend to make them taste more like a Natural. For the farmers, the advantage is that they can approximate some of the interesting characteristics of Natural processed coffee, with lower risk of mold and over-fermentation, and a slightly shorter dry time. The advantage for us is that we can experience intensely sweet coffees, and get even more character out of Central American coffee varietals.