An Insight on Coffee Processing

Coffee scientifically known as Coffea sp. is an elite plantation crop, famously known for its use in specialty beverages. Be it a hot cappuccino, latte, or some cold brew or Frappuccino, Coffee beverages are loved in all forms. Coffee, as we all know, is mainly used for its stimulating effect due to its caffeine content. It can also be used as an analgesic and as a memory enhancer. Several useful bioactive components like chlorogenic acid, trigonelline, and nicotinic acid are also present in coffee that make it beneficial to health.

The majority of the coffee consumers know that coffee is a bean that is ground and then added to a wet ingredient like milk or water to prepare a coffee beverage. But what about knowing; how the coffee plant is cultivated and harvested? what types and grades of coffee exist? What type of processing methods are used? In this article, we will give you an insight into coffee processing about how a small brown bean turns into your refreshing cup of hot and a cold beverage.

The Botany Behind Coffee Plant:

The coffee plant is a shrub belonging to the Family- Rubiaceae, which hosts dark green lanceolate leaves. The coffee shrub bears small, white flowers that are fragrant in nature. This shrub also gives rise to. This shrub grows in high tropical altitudes of 600 – 1200 m with an annual average temperature of 15–25°C and moderate moisture and cloudiness. The shrub hosts the coffee fruit known as “cherry” which ranges from a green to red color indicating the ripeness of the fruit. This fruit contains our known coffee beans. The commercial species of coffee are Coffea arabica (Arabica) and Coffea canephora (Robusta). There are several Coffea arabica varieties like  Bourbon, Typica, Caturra, Mundo Novo, Tico, San Ramon, Jamaican Blue Mountain. Coffea canephora variety is  Robusta.

The Anatomy Behind Coffee Cherry:

The coffee cherry consists of layers. The outer skin layer is called the exocarp. The middle thin layer of pulp is the mesocarp, followed by a slimy layer called the parenchyma. The coffee beans inside the cherry are covered in a paper-like envelope named the endocarp, more commonly referred to as the parchment. The Bean consists of two elliptical hemispheres with flattened adjacent sides which are each covered by seed skin called spermoderm, generally called silver skin in the trading world of coffee.

Source: https://www.darkmattercoffee.com/blogs

Harvesting of Coffee:

 In general, coffee species are harvested from November to December in the case of Arabica species and from January to February for Robusta. The harvesting of coffee is done when the coffee cherries are bright red all over.

The cherries are usually picked using different types of picking methods by hand – Fly picking, Main picking, Stripping, or cleanings.

• Fly picking: Done as the first picking in the season. Selective picking of ripe berries is done and continued till February.
• Main picking: Well-formed and fully ripened berries are harvested 4 to 6 times at a 10 – 15-day interval from Dec. Bulk yields are obtained during this period.
• Stripping: During the Final harvest, this type of picking is done where berries left on the plant are hand-picked irrespective of the referring stage.
• Cleanings: this type of picking consists of a collection of all the dropped berries that are collected.

Processing of Coffee:

After harvesting, the coffee is processed mainly in two ways, either wet processing or by dry processing. The method of processing depends on what type of coffee is required as if parchment or cherry coffee is needed.

1. Wet processing: This type of processing of coffee yields parchment coffee and this method involves pulping, demucilaging and washing, drying of coffee beans.  Here, the coffee cherry is squeezed in a pulping machine to remove the outer fleshy layer and obtain just the bean. This bean with mucilage is fermented and then washed and dried either by sun/tray drying which may take up to 1-2 days. There may be a risk of contamination due to over fermentation of the beans which may degrade the quality of the bean.
2. Dry processing: In this type of processing, the coffee cherries are immediately dried after harvesting by sun-drying/solar artificial driers. It takes about 12-15 days under bright sun for the cherry to dry completely. The dried cherry is now hulled to separate the bean and then winnowed. This method is comparatively better than the wet processing as it is environment friendly even though it is time taking. If proper drying of the cherries is done, then high-quality beans with exclusive flavor and aroma can be obtained.

Roasting of Coffee:

The beans obtained either by wet/dry processing now undergo a process called roasting. Roasting is an important procedure in coffee processing as it determines the color and flavor of the coffee bean. Usually, a typical roasting process takes place by drum/hot air roasting at about 200 degrees Celsius for 15-20 minutes based on requirements. The roasting causes an increase in the volume of the bean , changes the color of bean from green to brown, and makes the bean brittle. Typically, there are four types of roasts of coffee. They are light, medium,medium-dark, and dark roast.

 

Type of roast	Color and Flavor	Bean Surface
Light	Light brown and mild	Non-oily
Medium	Medium brown and strong	Non-oily
Medium-dark	Rich dark brown with a slightly bitter aftertaste	Barely oily
Dark	Dark Brown Black with a pronounced bitterness	Very Oily

Source: https://www.cafebritt.com/

Grading, Sorting, and Packaging of Coffee:

After roasting, grinding of roasted beans is done in rolling mills for obtaining a ground texture of coffee. Usually, 8-10-hour grinding is required for ground coffee. Arabica and Robusta beans are primarily sorted and classified as washed (parchment or plantation) and unwashed (natural). They are further classified into 25 grades based on the size of beans and the number of imperfections. Superior grades are Arabica Plantation A, Arabica Cherry AB, Robusta Parchment AB, and Robusta Cherry AB. The major types of grades are :

a. Grade 1: Specialty Grade: no primary defects, 0‐3 full defects, sorted with a maximum of 5% above and 5% below specified screen size or range of screen size, and exhibiting a distinct attribute in one or more of the following areas: taste, acidity, body, or aroma. Zero Quakers allowed. Moisture content between 9‐13%.

b. Grade 2: Premium Grade: Same as Grade 1 except a maximum of 3 Quakers. 0‐8 full defects.

c. Grade 3: Exchange Grade: 50% above screen 15 and less than 5% below screen 15. Max of 5 Quakers. Must be free from faults. 9‐23 full defects.

d. Grade 4: Standard Grade: 24‐86 full defects.

e. Grade 5: Off Grade: More than 86 full defects.

After grading the beans as whole or after grinding are packed in glass jars (for ground powder), jute bags/sacks ( beans ) , paper bags ( for both beans and powder form).

Now we know that just like any other food or beverage, even coffee ends up in our cup of refreshment after going through a lot of processing.