Soaking Robusta beans in syrup makes them almost indistinguishable from Arabica, and creates a more stable aroma in storage.
Student and Staff volunteers were unable to tell the difference between pure Arabica coffee and a blend made with syrup-soaked Robusta beans and just 20% Arabica. Without treatment, Robusta became detectable in blends when Arabica dropped below 80%. The paper, published last year in the journal of Food Chemistry by scientists at the University of Nottingham, also found that naturally-occurring fruit sugars (fructose) were most effective at disguising the beans.
The treated beans can also be stored for longer after roasting without degradation. “The aroma of [Robusta treated with fructose] was more stable during 6 weeks of storage compared with Arabica”, said the researchers.
According to the World Bank, Robusta is significantly cheaper than Arabica. In December 2019 Robusta was $1.63/kg and Arabica $3.45/kg. To put this research into perspective, most consumers can’t tell the difference between a $3.45/kg pure Arabica coffee and a $1.99/kg syrup-soaked Robusta blend.
Economics aside, there are environmental reasons for choosing Robusta beans. Robusta is easier to grow, thriving at lower altitudes than Arabica, and is less vulnerable to pests or bad weather.
A similar approach, the Torrefacto process, uses sugar during roasting to disguise the taste of Robusta. This new research shows that sugar can be used at the pre-roast stage, which also helps preserve bean aroma.