How Coffee Is Processed - What Happens Before Beans Get To The Roaster
We all know coffee grows on plants. The fruit of the coffee plant is actually more like a cherry than a bean—the fruit is even called cherries. And the seeds inside are what we call beans. But how do we get those beans? This week we’ll take a look at how coffee beans are processed prior to roasting.
Before ProcessingLet’s run through a super quick overview of pre-processing to see how we get there.
Growing Coffee – this is, of course, the first step in the coffee business. Coffee must be planted, nurtured, and grown. Ideal growing conditions are found along the equator (you can check out our virtual coffee tour here). Ripening – Part of the growing process, allowing the fruit to ripen is a necessity. Once the cherries turn red, they are ready for the next step. Harvesting – Whether by hand or machine, once the cherries have ripened they must be removed from the plants.Once the steps are broken down like this, it doesn’t look so difficult, but finding the perfect place with ideal growing conditions, keeping the plants pest and disease-free, and harvesting are all a lot of work.
ProcessingNow we’re on to the fun part. What exactly does processing entail, though? It actually depends on how the fruit is being processed. Yes, there is more than one way to process coffee and each can affect the flavor of the bean. Dry processing and wet processing refer to the beginning steps of processing cherries to beans. Dry This is the oldest method of processing beans. Once the cherries are picked, they are laid out on drying surfaces—usually raised concrete patios in full sun. They are raked often to ensure even drying and to prevent spoiling. At night and when it rains the cherries are covered to prevent them from getting wet. It takes several weeks for this process. The batch of cherries is considered finished when the moisture content reaches 11%. Wet When wet processing coffee cherries they are put through a machine which uses water to remove the skin and pulp from the beans. The beans are then separated with the ripe beans sinking to the bottom of the vat of water while unripe beans float. The beans are then passed through rotating drums which separate the beans by size. They are then sent to fermentation tanks for 12 to 48 hours to remove the mucilage (the slimy layer of pulp remaining on the bean. Finally, the beans are sent through more water channels to rinse off what is left of the mucilage before being sent to dry. The beans will be spread out on drying surfaces just like in the dry processing method until they are at 11% moisture. This may also be accomplished by machine.
MillingThe next step in processing coffee is milling. During this step the dry processed coffee is hulled which removes the dried husk (skin and pulp) as well as the parchment skin (the thin layer that holds the two seeds/beans together). The wet processed coffee will simply be hulled of its parchment layer. In some processing plants, the beans will be polished to remove any remaining silver skin or other bits of husk.
SortingOnce the beans have been cleaned they will then be sorted. Sorting is done by size and weight then quality.
Size and Weight – The first method to sort by size and weight is with a variety of screens. The smaller beans fall through the screens (along with any remaining sticks or chaff). The second method is with puffs of air. The larger and heavier beans fall into bins close to the air source while smaller and lighter beans are blown into bins further away. Another method is the gravity table which has a tilted tabletop that vibrates side to side causing the heavier beans to gravitate to one side of the table while the lighter beans vibrate to the other. Another widely used method for sorting is by hand.
Quality – Determined by color, this method is almost exclusively done by humans. Though there are machines which can sort by color, with beans falling past sensors and puffs of air removing the undesired beans, these machines are expensive and not widely used.
GradingThe final step in the usual processing of coffee beans is grading. This is determined by where the coffee is grown, how it was prepared, the imperfections on the beans, and the taste.
But Wait, There’s MoreThe steps above are the main steps in processing the majority of coffee. But there are more steps for other coffees.
Decaf Decaffeinated coffee must be processed prior to roasting to remove caffeine. This can be done by a couple of methods. The first and most commonly used method in the US is through CO2 extraction. Coffee beans are moistened and are put in contact with supercritical CO2 at a pressure of 4,000 pounds per square inch and temperatures of 194 deg F to 212 deg F. This method removes around 97% of the caffeine. In another method the beans are moistened with an ethyl acetate solvent which extracts most of the caffeine. The beans are then steam-stripped to remove the solvent. This solvent can be reused after the caffeine has been recovered from it. The decaffeination method which is considered to be the healthiest is the Swiss Water Process. In this process, osmosis causes the caffeine to leave the beans. The green coffee beans are saturated with Green Coffee Extract (GCE) which then causes the caffeine to leave the lower concentrate of caffeine in the beans to move to the higher concentrate of caffeine in the GCE. Aging A final step in processing prior to shipping is the aging process. One of the most well-known aging processes is monsooning. In this, coffee processors are recreating the conditions coffee were once subject to during the transportation by ship. Today, the beans are held in open warehouses at port to allow the salty sea air to age the beans.So that’s the processing process of coffee beans. Once the beans go through these steps they are stored and then shipped to roasters. Then, when the coffee is ordered, us roasters get to work!