Coffee Cherry Structure Characteristics! (Including Anatomy Diagram)

We often drink coffee, but few people have seen coffee beans, and even fewer have seen coffee cherries. Some industry friends say that coffee is actually a type of fruit juice, but FrontStreet Coffee doesn't quite agree. Juice is a liquid product made from fruit through physical methods such as pressing, centrifugation, or extraction, generally referring to pure juice or 100% juice. Coffee, however, is a beverage made by using coffee beans (seeds) that are roasted and then extracted with water to dissolve soluble compounds. It is not the juice of coffee cherries.

Coffee Growing Regions

Most coffee growing regions worldwide are located in tropical areas between the Tropic of Cancer and Tropic of Capricorn, which we call the "Coffee Belt" or "Coffee Zone" in English. As a tropical cash crop, coffee trees grow in the excellent climate conditions of the coffee belt, where there is direct sunlight year-round, abundant heat, and sufficient rainfall, with an average annual temperature above 20°C. However, not all coffee tree varieties can tolerate high temperatures, high humidity, and strong light. For example, some Arabica coffee trees cannot withstand high heat and humidity, and are often planted at higher altitudes. If light is too strong, they also need shade treatment, which is how "rainforest coffee" and "shade-grown coffee" got their names.

Coffee Cherries

Coffee cherries are very small, similar to cherries. Mature coffee cherries are red (special varieties not discussed here), also known as coffee cherries. There are three main original species of coffee: Arabica (low yield, delicate, but high quality), Robusta (highest yield, easy to grow, but lower quality), and Liberica (gradually disappearing variety, not discussed here).

Coffee cherry harvesting is very hard work. Brazil uses machine harvesting, but most premium beans require manual harvesting because coffee cherries mature at different times, requiring several rounds of picking.

The anatomical diagram clearly shows that coffee beans are the middle part. The fruit skin and pulp must be removed during processing. The silver skin, which is the seed coat, also falls off during roasting. The following are respectively the exocarp, mucilage layer, and endocarp.

The exocarp consists of 1-2 layers of cells, with structural characteristics similar to biological epidermis, having a cuticle and stomata. When coffee cherries are unripe, the parenchyma cells of the exocarp mostly contain chloroplasts, which transform into chromoplasts when mature. Depending on the degree of ripeness, the outer skin of coffee cherries gradually changes from green to red. From a biological perspective, the coffee pulp belongs to part of the fruit skin, developed from the plant's ovary wall. Coffee pulp contains sugars and acids, with honeydew melon-like sweetness and clear, pleasant fruit acidity.

The coffee mucilage layer is a heteropolysaccharide between the pulp and the endocarp (parchment), with a smooth, slippery texture that is difficult to dissolve in water. The mucilage part has the highest sugar content in coffee cherries and is an important component during coffee processing fermentation. For example, in honey processing, the more mucilage retained, the more obvious the fermentation sensation of coffee beans will be, and the sweetness will also be more pronounced. The parchment consists of parenchyma cells and serves to protect the coffee beans. The silver skin is a very thin film between the parchment layer and the coffee bean, belonging to the cytoplasmic membrane.

The fruit pit, which is the coffee bean, belongs to the seeds of the coffee tree. Typically, one coffee cherry contains two coffee beans. Because their touching sides are flat, they are called flat beans. Some coffee cherries have one underdeveloped bean during growth, allowing the other to have enough growing space, presenting an oval shape, so they are called peaberbs. The split in the middle of coffee beans belongs to the embryo part, which develops into leaves and stems after breaking through the coffee seed coat.

After processing and drying, a raw coffee bean has a moisture content within 13%. The moisture content of coffee beans does not significantly affect the aroma and taste of coffee; rather, what affects the flavor is the proportion of anhydrous compounds hidden within the coffee beans. After raw coffee beans are roasted into mature beans, many chemical changes occur within the beans. New substances are continuously generated, and the aromatic substances in coffee are produced at this time. After coffee cherries are picked, they become the raw coffee beans we commonly see through washing or drying. The raw beans are then roasted at high temperatures to become roasted beans. The roasted beans are ground into coffee powder, and the coffee powder comes into contact with water for extraction to become the black coffee we drink. No additives are added throughout the entire process!

For professional coffee knowledge exchange and more coffee bean information, please follow Coffee Workshop (WeChat official account: cafe_style)

For more specialty coffee beans, please add FrontStreet Coffee on private WeChat, WeChat ID: qjcoffeex

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