All about robusta: what it is, and what it might be

A primer on robusta coffee on a blog with over 400 posts seems a little tardy. For the most part, the message to consumers who are looking for high-quality coffee grown in a sustainable manner has been to simply avoid nearly all readily-available coffees containing robusta. But the world is changing, and we may all be getting to know robusta a little better in the future. It seems fitting to offer a little introduction.

What is “robusta”?
There are over 100 species of the genus Coffea in the world, and all are native to tropical Africa and some Indian Ocean islands. Two species, C. arabica and C. canephora, are commonly grown commercially. Coffea canephora is commonly referred to as “robusta,” and makes up about 25 to 40% of the coffee grown for consumption. Some consider only the upright forms of C. canephora to be called robusta, with spreading forms called “Nganda.”

Robusta grows in hotter (22 to 26 C), more humid climates than arabica coffee (18—21 C), and at lower elevations (from about 200 to 900 m). It has large leaves, deep roots, and flowers and fruits in globe-like clusters. It tends to be more hardy and disease-resistant and grows better in the sun than arabica, and it also tends to have higher yields. Robusta has a higher caffeine content (30 to 50% more) than arabica. While arabica coffee  is self-pollinating, robusta requires cross-pollination by insects or wind. Robusta cherries take a little longer to ripen, ten or eleven months versus around nine for arabica. Robusta is a diploid with 22 chromosones, as are all other species of Coffea except arabica, which is a tetraploid with 44.

Because of its heat tolerance, and the desire to produce high yields, robusta coffee is often grown at high densities in full sun. Large yields require high inputs of fertilizer and water. In countries where robusta cultivation has been encouraged and expanding, such as Vietnam, shade agroforestry systems and native forests have been removed in favor of growing the coffee in full sun.

History

Native to equatorial Africa, robusta was not really planted until coffee leaf rust wiped out much of the arabica coffee in the world in the late 1800s. Robusta was found to be quite resistant to the fungus, as it is to some other troublesome diseases and pests. Now, robusta is grown in Africa, including in Uganda, CÁ´te d’Ivoire, Cameroon, and the Democratic Republic of Congo; and in Asia, including Java, Timor, Sri Lanka, Sumatra, and above all, Vietnam. India, Mexico, Brazil (where a mild variety called Conilon/Kouillou is cultivated), and Guatemala grow both robusta and arabica. The largest grower is Vietnam, with over a half million ha devoted to robusta coffee, versus fewer than 30,000 ha in the mid-1980s.

Quality

Robusta beans tend to be more bitter and harsher than arabica. Words often used to describe robusta include rubbery, cereal or-grain like, flat, musty, or woody.

There are two primary uses for robusta. One is to add body and crema potential to espresso blends, and the other more widespread use is as a cheap filler in grocery store blends. Since so much is used in blends, yield and low cost are emphasized, not quality. Instead of focusing on only ripe cherries during harvest, robusta is often strip-picked, where all cherries are removed from the tree whether they are ripe or not. Less care is taken in processing; usually cherries are laid out to dry after harvest, without any further sorting.

In order to counter the unpleasant flavors of the robusta used in inexpensive coffee, multinational roasters have devised various methods to treat the beans, such as pre-drying, steaming, mixing it with a fatty material then soaking it in acetone, or roasting it so that “heavy, roasted burnt notes are developed” before blending. Yum.

Another way robusta is used is genetically — to confer some resistance to coffee rust and other pests and diseases into higher-quality arabica coffee. A hybrid between robusta and arabica from Timor, called Hibrido de Timor (HdT), has become the basis of a number of other varieties bred for their resistance to rust and other diseases. Generally, HdT is back-crossed with various arabica varieties such as caturra. Examples of varietals with robusta heritage include Catimor, Colombia, Sarchimor, Costa Rica 95, Castillo, Tabi, Icatu, and Ruiru 11.  Improving the cup quality of robusta-derived hybrids is a major challenge, especially because…

…We may be seeing more of robusta

Climate change may be driving us towards robusta. Unpredictable weather, including more frequent and prolonged rainy periods and higher temperatures, increase the incidence of coffee rust, coffee berry borer, and other pests and diseases. The replacement of heirloom varieties of arabica with disease-resistant varieties is already underway in countries like Colombia and India. Researchers are also exploring drought and heat tolerant coffee — and again, robusta genes play a role.

Further, rising global temperatures also mean that areas that are appropriate today for the cultivation of arabica coffee — cooler, upper altitudes — will likely become unsuitable within a few decades (arabica could move upslope, if land is available). However, these areas may support robusta production. If this conversion occurs, will robusta be grown under shade, or will shaded arabica coffee plantations or forests be replaced by robusta grown in sun monocultures?

So more robusta may be in our future. Some initiatives regarding improving the quality of robusta are already underway. In 2009, a number of workshops were held focusing on establishing standards for high quality robusta. Right now, this initiative is centered around cupping protocol and vocabulary, physical grading, and roasting profiles. Then energy needs to be directed at researching what creates high quality, including growing conditions and husbandry. Hopefully, that will lead to cultivation methods that incorporate biodiversity preservation.

Resources and further reading

DeMatta, F. M. 2004. Ecophysiological constraints on the production of shaded and unshaded coffee: a review. Field Crops Research 86:99-114.

Eakin, H., Winkels, A., and J. Sendzimir. 2008. Nested vulnerability: exploring cross-scale linkages and vulnerability teleconnections in Mexican and Vietmanese coffee systems. Environmental Science and Policy 4:398-412.

Leroy, T., R. Fabienne, B. BenÁ³it, P. Charmetant, M. Dufour, C. Montagnon, P. Marraccini, and D.Pot. 2006. Genetics of coffee quality. Brazilian Journal of Plant Physiology 18: 229-242.

Marsh, A. 2007. Diversification by smallholder farmers: Viet Nam Robusta Coffee. Agricultural Management, Marketing, and Finance Working Document No. 19. FAO, United Nations, Rome.

Van Der Vossen, H.A.M. 2009. The cup quality of disease-resistant cultivars of arabica coffee (Coffea arabica). Experimental Agriculture 45: 323-332.

I’ve added additional material to my coffee bibliography as well.

Flowering robusta in India from Wikimedia Commons; robusta beans by Michael Allen Smith, under a Creative Commons license.

Posted in Background information