COFFEE PROCESSING LITERATURE REVIEW

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II. LITERATURE REVIEW

A. COFFEE PROCESSING

Coffee, one of the most popular drinks worldwide, is a process product from the bean of coffee fruits Coffea. Two commercially important species of coffee economically are Coffea arabica Arabica coffee which contribute to 60 of world coffee production and the rest for Coffea canephora Robusta coffee. Arabica coffee is grown in Latin America, Central and East Africa, India and Indonesia, while, Robusta coffee is grown in West and Central Africa, South- East Asia and Brazil Wrigley, 1988. Part of coffee trees that is used as commercial products is coffee bean which is contained inside coffee fruit. The coffee fruit has a smooth and tough pericarp in red-violet color when ripe. There is a soft yellowish mesocarp covered by pericarp. Then, there is thin yellowish endocarp called parchment. The silver skin covers each hemisphere of the coffee bean endosperm Purseglove, 1974. The composition of the coffee fruit or coffee berry is depicted in Figure 2.1. Figure 1 Composition of the coffee fruit or berry Esquivel, 2011 There are several steps to process raw coffee fruit into coffee beverages. The general steps in coffee processing are coffee fruit processing, roasting, and brewing as showed in Figure 2. Coffee fruit processing is a process to remove the fruit from the beans followed by drying process. There are two basic methods of coffee fruit processing, i.e. wet and dry methods. These two methods produce different flavor and aroma in the bean. In wet process, the fruit pulp covering the beans is removed by a depulper machine. The depulpers machine is used to completely removed the mucilage from the parchment Murthy et al., 2001. The fermentation in wet process is a process applied to break down the mucilage layer which will takes approximately 24-36 h for Arabica coffee and 72 h for Robusta coffee. After the fermentation process, the bean with the parchment is dried for 8-10 days under the sunlight to reduce its moisture until approximately 12.5 Murthy et al., 2001. Then, the parchment is removed to obtain the coffee bean. In dry process, the freshly harvested fruit is dried 12-15 days and the parchment is removed to get the bean. The bean from both the wet and drying process is further cured for coffee bean flavor and aroma development. During roasting process, green coffee bean is heated to the temperature ranging from 180ºC and 240 o C for 8 to 15 minutes, depending on the degree of roast required ICO, 2012. There are several chemical reactions pyrolysis occurred during the roasting process such as converting starches into sugar, breaking down of proteins and altering of the entire cellular structure of the bean. This process also creates the specific or unique flavor and aroma to the coffee bean. The process also lead to the releases some of volatile compounds such as caffeol coffee oil which responsible as coffee flavor. The basic principle of brewing process is providing time of coffee ground beans to submerge in the hot water. This process produces an extract with unique flavor and aroma 3 obtained from the fermentation process, the curing process, the roasting process, as well as the brewing process. This brewing process is not only produced the drink, but also generates coffee ground residue CGR as the side product. CGR is normally dumped directly to the bin. This causes a lot of environmental problems to the community. Figure 2 Processing of Coffee Fruit into Beverages FAO, 2012

B. COFFEE GROUND RESIDUE CGR