Microbial and biochemical dynamics during postharvest Fermentation to Improve the quality of robusta coffee (Coffea canephora)
Abstract
Robusta coffee (Coffea canephora) plays a strategic role in global coffee production due to its high productivity, agronomic resilience, and adaptation to lowland tropical ecosystems. Its distribution to the global market is hampered by inconsistent sensory quality, dominant bitterness, low acidity, and susceptibility to post-harvest defects. Fermentation is now positioned not only as a mucilage removal step, but as a controlled biotransformation process capable of modulating the bean’s chemical composition, aroma precursor profile, and sensory characteristics in a planned manner. This study seeks to integrate the roles of both spontaneous and controlled fermentation in enhancing the quality of robusta coffee, with a focus on the involvement of microbial communities, the breakdown of substrates, the creation of metabolites, and the development of volatile compounds. This study analyzes the microbiology of coffee fermentation, metabolite transformation, volatile profiles, and sensory evaluation to identify key mechanisms, technological advances, and research gaps. Growing evidence indicates that yeast, lactic acid bacteria, and acetic acid bacteria interact with mucilage sugars, pectin, amino acids, phenolics, and lipids, producing organic acids, alcohols, esters, aldehydes, and aroma precursors that determine post-roast flavor profiles. Technological interventions including starter culture inoculation, anaerobic fermentation, carbonic maceration, bioreactor systems, and temperature-assisted fermentation have shown significant potential to improve consistency and sensory differentiation. However, field-scale validation, parameter standardization, cost barriers, and adoption of innovative practices remain key challenges. Integration of the microbiome, metabolomics, volatile profiling, and process engineering is necessary to design precise and competitive robusta fermentations in the global specialty coffee market.