Enhancement of robusta coffee quality through selected natural substrate fermentation: volatile compound profiling and sensory evaluation

Abstract

Robusta coffee, an important agricultural commodity in Subang, West Java, frequently has lower sensory quality compared to products from other regions. This study investigated the potential of selected natural substrates in improving the flavor profile and sensory quality of Robusta coffee through controlled fermentation. Coffee cherries were fermented for five days with mung bean sprout extract, sugar or palm sugar, coconut water, and pineapple peel extract, supplemented with Saccharomyces cerevisiae as a starter culture. Post-fermentation, the beans were dried, dry hulled, and roasted to a medium level (Agtron 58-63) prior to analysis. Volatile compounds, profiled by solid-phase microextraction coupled with gas chromatography-mass spectrometry (SPME-GC-MS), were dominated by pyrazines, furans, phenolics, alcohols, aldehydes, and esters. Sensory evaluation by trained panelists revealed that fermentations with mung bean sprout extract, palm sugar, and coconut water enhanced aroma complexity and flavor balance, resulting in a cupping score increase of up to 8.8%. Sensory attributes included caramelly, floral, sweet potato, and brown sugar notes. These results highlight the importance of substrate selection for adjusting volatile composition and improving the sensory quality of Robusta coffee.