GC/MS-based metabolic profiling for the evaluation of solid state fermentation to improve quality of Arabica coffee beans.

Abstract

Coffee fermentation has been reported as one key process in aroma and flavor development of coffee. However, natural fermentation often results in inconsistent quality of coffee. In this study, second fermentation using isolates from feces of civet (Luwak) and Cilembu sweet potato were used to improve the quality of Arabica green coffee beans. The aim of this research was to improve the quality of various Arabica coffee from different origins in Indonesia by controlled-second fermentation. The Arabica coffee beans used in this study were from three origins in Indonesia: Kintamani-Bali (I), Aceh-Gayo (II) and Nagarawangi-Sumedang (III). The second fermentation was done using three bacterial isolates coded as BF5C(2); UciSp14; and AF7E which belong to Bacillus genus. Quality assessment of fermented coffee was performed by cupping test following Specialty Coffee Association of America (SCAA) protocol by licensed Q graders, GC/MS metabolite profiling, and total polyphenol content measurement. The controlled-second fermentation for 4-8h was successful to increase total polyphenol content well as to improve the complexity of coffee taste and coffee quality (cupping score > 84). Comparative GC/MS analysis showed that fermentation of coffee beans resulted in alteration of metabolite profiles of coffee beans compared with control, while still maintaining the characteristics of coffee based on each origin. The controlled-second fermentation was effective to increase the quality of coffee and alter metabolite composition of coffee that were associated with changes in taste profile of coffee. This report may serve as basis for producing coffee with better taste quality with higher polyphenols content through standardized fermentation production in industrial scale.