Researchers have carried out a comprehensive physical and cup quality assessment of Arabica coffee (Coffea arabica) from three regions in the Kafa Biosphere Reserve, a coffee conservation area in the southwestern part of Ethiopia.

Alemayehu Tassew et al. confirm that, in addition to the selective hand-picking of red-ripe berries, better quality coffees can be obtained by using the dry processing method within the recommended range of green bean moisture content. Image credit: Daniel Ramirez.

Coffee is a commercially valuable commodity and is the most popular beverage globally.

For many producing countries, it is a major foreign currency source and contributes a lot to tax income and gross domestic product.

For coffee-producing countries, the production and supply of coffee for the international market is a challenging process since its value is governed by bean quality.

In 2020, Arabica coffee accounted for 59.27% of the world’s coffee production.

In Ethiopia, coffee is grown on 0.76 million ha of land, and more than 529,000 tons of coffee beans were estimated to be produced in the 2019-2020 cropping season.

This makes Ethiopia Africa’s leading coffee-producing country; it produces and exports 7.35 and 3.98 million 60-kg bags of coffee beans, respectively.

In the 2017-2018 production year, 34% of Ethiopia’s exports were covered by coffee.

“Arabica coffee is an integral part of the southwestern Ethiopian tropical forest agroecology,” said lead author Addis Alemayehu Tassew, a researcher in the Bonga Agricultural Research Center at the Southern Agricultural Research Institute and the Department of Horticulture and Plant Sciences at Jimma University.

“The forest ecosystems create conducive conditions for producing distinctive quality coffee. They also are a good source of income for farmers.”

“Coffee production and processing systems are the primary factors that determine the overall quality of coffee produced in a specific environment.”

“Many factors influence the growth and development of coffee plants, including: altitude, rain-fall pattern, temperature, relative humidity, light, moisture, and soil nutrients.”

“These factors then influence the quality of the bean, and of the biochemicals inside the bean that influence the coffee quality.”

In their research, Alemayehu Tassew and his colleagues studied coffee crops from Gimbo, Gawata, and Decha districts of the Kafa Biosphere Reserve.

The growing regions ranged from over 450 m (1,500 feet) high to over 3,350 m (11,000 feet).

The temperature and rainfall varied at each site, as did some of the growing practices.

This gave the authors the data on production and growth habits that may influence coffee bean quality.

To study bean processing’s influence on bean quality, they collected ripe cherries (unprocessed beans) at study sites from October to December 2018.

Each sample was divided into three equal amounts to apply the three processing methods: dry (coffee cherries were sundried), semi-wet (coffee cherries were pulped with machine and hand washed, then parchment coffees with mucilage cover were sundried) and wet processing (coffee cherries were pulped with machine and then fermented).

Professional coffee testers participated in the testing phase of the research. They participated in the physical, raw, and cup testing procedures.

“We need to keep bean moisture content high within the recommended range to get better cup quality, specifically coffee acidity,” Alemayehu Tassew said.

“The study confirms that better quality coffees come from selective hand-picking of red-ripe cherries.”

“In addition, it is better to use the dry processing method within the recommended range of green bean moisture content.”

The results appear in the journal Agrosystems, Geosciences and Environment.

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Addis Alemayehu Tassew et al. Location, production systems, and processing method effects on qualities of Kafa Biosphere Reserve coffees. Agrosystems, Geosciences and Environment, published online May 19, 2022; doi: 10.1002/agg2.20270

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