All About Green Coffee Beans (Kopi Beras/Kopi Hijau)

The green coffee beans

The overall quality and chemical composition of green coffee beans are affected by many factors, such as the composition of the soil and its fertilization, the altitude and weather of the plantation, and the final cultivation and drying methods used. Coffee plants are grown in tropical and subtropical regions of central and South America, Africa, and South East Asia, mainly in regions with temperate and humid climates (Schenker 2000). Brazil is by far the largest grower and exporter of green coffee beans in the world followed by Vietnam, Colombia, Indonesia, Ethiopia and India – producing nearly 2.5 million tons of green coffee beans per year (Franca & Oliveira 2009).

The genus coffee belongs to the botanical family of Rubiaceae and comprises more than 90 different species (Davis 2001). However, only Coffea Arabica (Arabica), Coffea canephora (Robusta), and Coffea liberica are of commercial importance (Schenker 2000). Arabica accounts for approximately 64% while Robusta accounts for about 35% of the world’s production; other species with not much commercial value like Coffea liberica and Coffea excelsa represent only 1% (Rubayiza & Meurens 2005). Due to its more pronounced and finer flavour qualities, Arabica is considered to be of better quality and accordingly command higher prices (Valdenebro et al. 1999). 

Coffee cherries are harvested when they become bright-red, glossy, and firm, either by selective hand-picking or non-selective stripping of whole branches or mechanical harvesting. The hand-picking method is very time-consuming, but results in a superior product quality because only ripe cherries are selected. After harvesting, the coffee fruits are separated from the pulp, which is carried out by dry or wet processing (Clarke & Macrae 1987; Illy & Viani 1995). 

The dry process is simple and inexpensive. The whole cherries are dried under the sun in open air, followed by the separation of the hull (dried pulp and parchment) mechanically to yield the green beans. On the contrary, the wet process requires greater investment and more care, but results in a superior coffee quality. In the wet process, the pulp of the coffee cherries, which is made up of exocarp and mesocarp, is removed mechanically, but the parchment remains attached to the beans. After drying either under the sun or in a dryer, the parchment is removed to produce the green coffee beans. Bean size, color, shape, processing method, crop year, and presence of defects, are some of the parameters used to evaluate the quality of green coffee beans (Banks 2002).

Coffee cherries are harvested when they become bright-red, glossy, and firm, either by selective hand-picking or non-selective stripping of whole branches or mechanical harvesting. The hand-picking method is very time-consuming, but results in a superior product quality because only ripe cherries are selected. After harvesting, the coffee fruits are separated from the pulp, which is carried out by dry or wet processing (Clarke & Macrae 1987; Illy & Viani 1995). The dry process is simple and inexpensive. The whole cherries are dried under the sun in open air, followed by the separation of the hull (dried pulp and parchment) mechanically to yield the green beans. On the contrary, the wet process requires greater investment and more care, but results in a superior coffee quality. In the wet process, the pulp of the coffee cherries, which is made up of exocarp and mesocarp, is removed mechanically, but the parchment remains attached to the beans. After drying either under the sun or in a dryer, the parchment is removed to produce the green coffee beans. Bean size, color, shape, processing method, crop year, and presence of defects, are some of the parameters used to evaluate the quality of green coffee beans (Banks 2002). notes of the coffee blend (Parliment & Stahl 1995). Besides contributing to balanced flavour profiles, Robusta coffee is often blended with Arabica for cost reduction purpose. Robusta beans are lower in cost since the crops are more hardy to grow (more resistant to infestation) and easier to harvest (grown in regions of low elevation) than the Arabica counterpart.

Defective beans (black or brown, sour, immature, insect-damaged, split), which represent about 11-20% of coffee production, can impact the flavour of the roasted products. Mazzafera compared the chemical composition of defective beans and non-defective beans. The researcher found that non-defective beans were heavier, had higher water activity, and lower titratable acidity than the defective beans. The content of sucrose, protein, 5-caffeoylquinic acid, and soluble phenols were also higher in non-defective coffee beans (Mazzafera 1999). Nevertheless, the antioxidant level in the defective beans, especially chlorogenic acids, remains high which may be a good source of antioxidant or radical scavenger for other food applications (Nagaraju et al. 1997).

After harvesting, green coffee beans should be dried to 10-14.5% moisture content and stored below 26oC under dry environment (50-75% RH) to maintain the bean quality and to prevent the growth of mould (Gopalakrishna Rao et al. 1971; Kulaba 1981; Betancourt & Frank 1983). Under optimal storage conditions, green coffee beans may be stored for more than 3 years (Bucheli et al. 1998). Usually, green coffee beans are packaged in natural jute, sisal or burlap bags, although high quality beans may be packaged in high barrier synthetic vacuum packages fabricated from synthetic thermoplastic polymers. Cupping is a method to detect the early stages of coffee deterioration. Bucheli and others (Bucheli et al. 1996) reported that glucose was a sensitive marker for green coffee bean quality during storage. Glucose is present only in trace amount of good quality green coffee, and the content will increase when deterioration occurs (Wolfrom & Patin 1965; Bucheli et al. 1996).

Source : Physicochemical Changes of Coffee Beans During Roasting

JAVA PREANGER COFFEE ADDICT

Fadillah Satria

 

FTIP TMIP UNPAD

fadilprojectkopi@gmail.com