CFRR – What is the basic taste of robusta coffee beans? How is the quality assessment of robusta conducted?
The growth of coffee plants
Through the ages and legends about the origin and formation of coffee, it is known that the wild coffee tree (Coffea arabica) was a plant in Ethiopia around 850 AD, and the Robusta coffee has a more recent history around 1870 and was first grown in the Congo Basin (Smith, 1985).
The highland forests of Ethiopia and South Sudan are considered the birthplace of arabica coffee (Stoffelen and coworkers, 2008). The history of popularization of arabica coffee began around the 8th century when it was shipped from Ethiopia to Yemen and then expanded to other tropical countries around the world such as India, Sri Lanka, Java, and Indonesia.
The popularization of robusta coffee trees started near the Lomani River, a tributary of the Congo River in Central Africa then was transported from Congo (Belgium) to Java and spread and grown in countries such as India, Uganda, and Ivory Coast (Juan and coworkers, 2017).
Central Africa seems to be the source of the commercially important Coffea species, C.arabica and C.canephora (robusta). The species C.canephora is native to the humid forests of tropical Africa with two main genetic types initially, kouilou and robusta, while kouilou has a low diversity, robusta has a variety of growth and Due to different ecological growing conditions, researchers have called robusta a representative species of C.canephora (Dusser and coworkers, 1999; Gomez and coworkers, 2009). Robusta coffee trees began to grow significantly in the early 19th century because of damage caused by CLR (coffee leaf rust fungus) in C.arabica plantations in Asia (Charrier and coworkers, 1997).
The altitude affects the quality of Robusta coffee beans
Many studies on the quality of brewed coffee and fine robusta classification conducted by CQI have determined the influence of altitude on the quality of a cup of coffee. By observing, robusta coffee trees grown in Tanzania at an altitude of 1500m in the volcano has a fruity taste with a smoothness, sourness, and sweetness comparable to high-quality arabica coffee beans. Robusta coffee growing in India at an altitude of over 1000 meters has a unique flavor, acidity, and sweetness. Robusta coffee grown below 1000m produces a cup of coffee with light, rich flavor or pronounced caramel and cocoa notes (Ted and coworkers, 2017). Although flavor diversity can depend on plant genetics, high altitude cultivation leads to growth and development that contributes to inherent flavor stability.
Role of biochemicals in robusta coffee beans
The C.canephora’s market value has always been lower than that of C. arabica, because arabica coffee seems more acid and less caffeine than robusta. Therefore, it is more suitable for consumer taste with a better taste sensation. And using both wet and dry processing methods did not significantly improve the quality of robusta coffee (UCTF, 2008; 2009). Beverage quality is influenced by the content of biochemical compounds present in coffee beans. The high amount of chlorogenic acid and caffeine in robusta causes adverse effects on beverage quality the concentrations of sucrose and trigonelline that produce flavor in coffee are only moderate (Clifford, 1985; Ky and coworkers, 2001a).
Robusta coffee has medium sweetness and acidity, the aroma of roasted nuts, and is prominent in intensity compared to arabica beans. The final quality of the coffee has been determined by a sensory analysis performed by Q-Graders (Di and coworkers, 2014; Bhumiratana and coworkers, 2011). Volatile or non-volatile chemical constituents are responsible for the distinctive flavor and coffee aroma (Carrera and coworkers, 1998). The final quality of coffee is related to the chemical composition of the roasted coffee beans due to the extensive chemical interactions that occur during the roasting stages (Ribeiro and coworkers, 2014). Chemical perspective has known that the proportions of caffeine, chlorogenic acid, and reducing sugars have different depending on the genetics and groups of arabica or robusta (Alonso-Salces and coworkers, 2009; Liu and coworkers, 2012); Tfouni and coworkers, 2012; Wei and coworkers, 2010).
Robusta coffee bean cupping review
The varieties of robusta coffee have lower quality than arabica coffee, although in countries such as Vietnam and Indonesia there is significant robusta growth every year. For those who are used to the taste of arabica coffee, robusta is not a good alternative. However, for many coffee drinkers looking for the presence of caffeine, the potential replacement is significant when the price of arabica is much higher than the price of robusta (Reuters, 2013).
CQI has taken steps to develop a Q program for robusta coffee based on the highly successful Q arabica model, clearly demonstrating higher quality leading to higher prices. Physically taxonomically, robusta seeds are relatively similar to arabica seeds with defects that are also very similar, the difference lies in the chemical composition due to plant genetics (Ted and coworkers, 2017). CQI started a two-year trial with 53 coffee experts from 18 different-countries and robusta samples from Uganda, Tanzania, Brazil, Central America, India, Indonesia, and Vietnam. Experts have unequivocally proven that robusta coffee can distinguished by the origin and quality of the cup of brewed coffee. They rated on a 100-point scale with the same 80-point standard or more. That rate used to distinguish high-quality robusta coffee from commercial coffee. The term that named “fine robusta” chosen to distinguish it from “specialty arabica” (Ted and coworkers, 2017).
The cupping system to evaluate robusta coffee noted ten main attributes like aroma, flavor, aftertaste, bitter/sweet ratio, mouthfeel, balance, ratio salt/acid ratio, separation uniformity, cleanliness, and overall. Fragrance and taste defects and errors have also recorded.
In the aftertaste attribute in robusta, coffee is often dominated by the potassium content in coffee, with high content leading to a brackish aftertaste and low content leading to a salty aftertaste. Bitter/sweet ratio, both bitter and sweet taste sensations are present in robusta coffee. The fine robusta coffee has low bitterness and high sweetness, while commercial robusta beans have high bitterness and lower sweetness. The salt/acid ratio represents a pleasant and subtle flavor resulting from a distinguishable acidity and sweetness in the sample, the level of potassium and chlorogenic acid also contributes to this characteristic. This property demonstrates a striking difference in flavor between fine robusta and commercial robusta (Ted and coworkers, 2017).
Review of robusta coffee beans
An espresso with robusta beans will produce a dark brown or tiger skin crema. Its smoothness is a sign of good extraction, while the crema contributes to the increased “body” attribute that the robusta coffee is well known (Navarini and coworkers, 2004a). There is an interesting observation in India that when growing robusta coffee trees under the shade of fruit trees, the taste of brewed coffee tends to decrease bitterness with high brightness, flavors of fruit, nuts, and chocolate, besides the smoother mouthfeel. When grown close to pepper, the aroma of robusta becomes quite distinctive in brewed coffee (Ted and coworkers, 2017). These features are so far only sensory findings, and more scientific studies are needed to confirm these findings.
Commercial robusta often has a prominent aroma of toasted corn and a bitter taste beside the notes of woody odor and a dry, harsh mouthfeel. Wet-processed robusta coffee beans can soften negative notes and reduce bitterness with developing a soft, smooth mouthfeel and a bright sour taste. It is hard to apply wet processing with robusta because the mucilage processing is thicker and sticky than with arabica (Ted and coworkers, 2017).
The composition of substances in coffee beans plays a role in determining the aroma and quality of the cup of brewed coffee. Although the arabica and robusta beans is the same, their concentrations are very different when shown in the table below.
Robusta coffee is characterized by lower levels of carbohydrates (sucrose, oligosaccharides, mannans), lipids, trigonelline, organic acids (malic, citric, quinic), and 3-feruoyl-quinic acid (3-FQA). On the other hand, robusta beans are rich in caffeine, protein, arabinogalactans, CGA (except 3-FQA), total phosphates, ash (Ca salts), and transition metals (Fe, Al, Cu). These components are decisive for the quality differences and characteristics of roasted coffee beans (Luigi and coworkers, 2017). This imparts a darker flavor to the robusta bean, which makes it unsuitable for consumption.
Robusta beans contain significantly more total CGA than arabica, for which CGA is an important precursor of bitter compounds (Dorfner and coworkers, 2003), along with high levels of volatile phenols from the guaiacol group produce the characteristic woody, smoky, and roasted bean aromas that become prominent features in dark roasted robusta coffee (Luigi and coworkers, 2017).
It’s hard to assess the quality of a cup of robusta coffee because of the unremarkable flavor of robusta. However, fine robusta has a distinctive, more acceptable flavor that used to blend in espresso or by the drip method and can be used to prepare milk-based drinks such as cappuccino or latte. The market for the growth of fine robusta is balanced with arabica. Importers and exporters, roasters and diners need to know about the salient features, were found in fine robusta to distinguish it from commercial robusta are as specialty arabica.
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