Where does your coffee come from?
You may know that coffee is a plant and recognize that the beans come from a bright red coffee cherry. But what’s inside that coffee cherry and what does it mean for your cup?
The different parts of the coffee cherry have a bearing on the processing method and your coffee’s final profile. Let’s take a look at the basic anatomy of the coffee cherry to better understand our daily brew.
Understanding the Coffee Plant
The beans we roast, grind and brew to make coffee are the seeds of a plant. The coffee plant produces coffee cherries and the beans are the seeds inside.
Coffee trees can naturally grow to over 30 feet but producers prune and stump plants short to conserve the plant’s energy and to help in harvesting. Small trees have a better yield and quality and take up less space.
Each tree is covered with green waxy leaves that grow in pairs and coffee cherries grow along its branches. Depending on the variety, it takes three to four years for a coffee plant to produce fruit. The National Coffee Association (the leading trade association in the U.S.) states that the average coffee tree produces 10 pounds of coffee cherries per year, which results in about 2 pounds of green beans.
But there are different varieties of coffee and their beans have many different characteristics. Size, flavor, and disease resistance vary, among other factors.
The Layers of a Coffee Cherry
A coffee cherry’s skin is called the exocarp. It’s green until it ripens to a bright red, yellow, orange, or even pink, depending on the variety. Green coffee cherries shouldn’t be confused with green coffee beans, which are the unroasted seeds from inside the ripe coffee cherry.
Beneath the cherry skin is a thin layer called the mesocarp, more commonly known as the pulp. Mucilage is the inner layer of the pulp. There’s also a layer of pectin underneath the mucilage. These layers are full of sugars, which are important during the fermentation process.
Finally, we reach the coffee seeds, which are technically called the endosperm but we know them better as beans. There are usually two beans in a coffee cherry, each of which is covered by a thin epidermis known as the silverskin and a papery hull that we call parchment (technically the endocarp).
The parchment is usually removed in hulling which is the first step in the dry milling process. Machines or millstones are used to remove any remaining fruit and the dried parchment from the beans. Sometimes beans are sold with this layer intact as parchment coffee.
A silverskin is a group of cells that are strongly attached to the beans. These cells form to support and protect the seed. They come off during roasting when they are known as chaff.
Sometimes there’s just one seed inside a coffee cherry and it’s rounder and larger than usual. This happens in about 5% of coffee cherries and the beans are known as peaberries. Peaberries can be an anatomical variation of the plant or they can form when there is insufficient pollination. Sometimes the seed simply fails to grow, whether due to genetic causes or environmental conditions. Peaberries usually occur in the parts of the coffee plant that are exposed to severe weather conditions.
There’s some debate over whether peaberries have a sweeter and more desirable flavor and they are sometimes sold at a premium. Regardless of whether you think they taste different, their rounded shape allows for better rolling in the roasting drum, so roasters keep them apart from other beans to avoid an inconsistent roast.
How Anatomy Affects Your Cup
Coffee cherry skin and fruit are usually discarded but sometimes they are dried to make cassava for tea and other products.
It’s challenging to remove skin and mucilage from coffee beans and different processing methods have developed to do so. Each method has an impact on the flavor and profile of the final coffee.
For example, washed coffee has all of the flesh removed before drying. But in natural coffee, the fruit flesh is removed after drying. In honey processing, the skin (and sometimes part of the mucilage) is removed before drying but the remaining mucilage and other layers are removed after. Leaving the mucilage on results in a sweeter coffee with more body. It’s easier to understand if we compare both dry and wet post-harvest processes.
When coffee cherries are taken from the branch, they start to germinate. This uses the sugar in the seed. Germination stops when drying begins. Natural processed coffees go to the drying terrace earlier than pulped natural or washed coffees. Because of this, more sugars remain in the naturals and you end up with a sweeter coffee.
Washed coffees have clean, more consistent flavors that can show off a lot of acidity. Natural coffees have a lot more fruitiness, sweetness, and body.
The sugars of the mucilage also ferment during dry and wet processing; this affects the final flavor. Without careful monitoring and consistent drying, the unpredictable process of fermentation can produce undesirable qualities.