Characteristic of local Robusta cherries upon fermentation and roasting during wet coffee processing

Abstract

The unique chemical composition in coffee cherry offers a unique quality when it is processed. This study aimed to evaluate the characteristic of local Robusta coffee cherry when submitted to fermentation and roasting process via wet process. Local Robusta coffee cherry were divided to three groups namely Green B, Fermented and Roasted. Commercial samples namely Green N, Kopi Luwak and Green Z were also analysed as a benchmarking which representing the process involved. All the samples were evaluated for their antioxidant activity (AA) using ABTS and DPPH method including TPC analysis. Its organic acid, caffein and chlorogenic acid were also analysed using HPLC equipped with PDA detector. The AA values for both ABTS and DPPH methods showed similar trends and aligned with TPC results where Green N possessed the highest antioxidant value (IC50 160.6 ± 1.6 μg/ml, IC50 2007.5 ± 10.5 μg/ml, ABTS and DPPH respectively). The acetic acid concentration is in the range between 0.03-1.13 (%dry matter) while lactic acid concentration is in the range between 0.01-0.79 (%dry matter). Caffeine content was found at a higher concentration in Roasted (3.78 ± 3.5 mg/g) followed by Kopi Luwak (2.75 ± 0.5 mg/g) and Fermented (2.68 ± 0.8 mg/g) while chlorogenic acid was found at the highest concentration in Green B (0.40 ± 0.2 mg/g). Sample submitted to fermentation prior to roasting process gave impact on acetic acid, lactic acid, caffeine and CGA content. Acetic acid, lactic acid, caffeine and CGA are components that affect the quality of coffee as such offer a special characteristic of local Robusta coffee cherry.