Light-roasted coffee contains more antioxidants - study

MANILA, Philippines –  Results of a study conducted by Dr. Ruel M. Mojica, a grantee of the UP-NSRI/DA-BAR Post Doctoral and Senior Scientist Research Fellowship in Basic Research for Agriculture and Fisheries, show that light-roasted coffee gives the highest phenolic content and antioxidant activity among coffee samples subjected to varying degrees of roasting.

In his research titled “Influence of Roasting on the Phenolic Content and Antioxidant Activity of the Philippine Coffee,” Dr. Mojica found that the degree of roasting has a significant effect on the antioxidant activity of both Coffea robusta and C. liberica samples.

In his report, Dr. Mojica said roasted beans generally contain less polyphenols than green beans, since more than 60 percent of chlorogenic acid present in green coffee is degraded upon roasting.

Dr. Mojica said he found a “considerable increase” in phenolic content when the berries were light roasted. He said phenolic content begins to decrease in medium roast to very dark roast samples. 

It is believed that other polyphenolic substances in coffee samples are being produced upon application of a sufficient amount of heat. It was also observed that antioxidant activities decrease with an increase in the degree of roast.  

Antioxidant level was investigated by measuring the total phenolic content while the assay of antioxidant activities used the radical scavenging capacity and reducing power as parameters.

“Although several studies have been done on the chemical composition of crops, fewer studies have been made on the antioxidant activity of coffee in the Philippines. In fact, no studies have been reported on the chemical characteristics and antioxidant activity of Philippine coffee,” Dr. Mojica said, adding “if ever there were, these would be on Robusta only. Yet we have four varieties.”

Dr. Mojica said his study originally included only two varieties of Philippine coffee (C. robusta and C. liberica) and three degrees of roasting (light, medium, and dark roasts).

Given the luxury of time, he decided to include the varieties, C. excelsa and C. arabica, to complete the four commercially-viable varieties of coffee, and very dark roast as another degree of roasting.

“With the recent changes, the study has turned into a comprehensive one. So by the time it is completed, this will serve as baseline information on the antioxidant properties and phenolic contents of the four Philippine coffee varieties,” said the research fellowship grantee.

According to the Philippine Coffee Board, the Philippines is one of the few countries that produces four varieties of commercially-viable coffee: Arabica, Liberica (Barako), Excelsa and Robusta. 

Dr. Mojica, an assistant professor at the Cavite State University, said that by determining the antioxidant properties of each variety as affected by a certain degree of roasting, local coffee processors could use the information to produce better blends of coffee that have high antioxidant levels without sacrificing the taste, benefiting both their profit and the health of the consumers.

“Farmers, on the other hand, will be encouraged to plant coffee and will eventually regain their interest in engaging with the coffee industry,” said Dr. Mojica.