Changes in physico-chemical characteristics of robusta coffee (Coffea canephora) during natural process using simple solar dryer

Abstract

A simple solar drying technique was recently introduced for processing robusta coffee ( Coffea canephora) in Indonesia. It is considered a modification of the natural process commonly found in Indonesia. The objective of this work is to evaluate changes in the characteristics of coffee beans during the drying process. The results show that a significant reduction of moisture content and Aw takes place in the first 7 days of drying, followed by a slight increase of total sugar and total acids. The next 14 days of drying occurred at a lower rate, and the abovementioned parameters continued to decrease, but an increase in the pH and total phenols were observed. The yield of the process was 27.5%, and the moisture content of the green bean meets the Indonesian National Standard (SNI) of coffee. The water activity (Aw) of the green bean is considered low which could prevent growth of spoilage microorganism if stored properly. The levels of caffeine and chlorogenic acids in the green bean are considered low for robusta coffee.