Natural or Induced? How Fermentation Dynamics Alter Arabica Coffee Aroma and Bioactive Compounds

Apart from coffee’s commercial importance to Brazil, the growing global demand for specialty coffees stands out, stimulating the search for quality-enhancing technologies. Fermentation may be a strategy in this regard, enabling both the production of aromatic compounds, which positively influence the aromatic profile, and an increase in the phenolic compound content. To evaluate the effect of coffee fermentation (Coffea arabica L.) on its sensory aromatic profile and phenolic compound content, this study fermented coffee cherries from the Paraíso and Arara cultivars, varying the microorganisms involved (spontaneous— natural microbiota present —or induced —Saccharomyces cerevisiae yeast and the lactic acid bacteria Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus) and the fermentation time (65 and 112 hours), resulting in a total of eight treatments. All other processing steps (harvest date and location, fermenter size, drying time and temperature, method of husk removal, roasting time and temperature) were the same for all samples. The aromatic profile was evaluated through sensory analysis using 100 untrained panelists. The phenolic compound content was analyzed using spectrophotometry and high-performance liquid chromatography (HPLC). Parameters such as yield, color (Hunterlab L, a, b system), soluble solids (° Brix), and pH were also investigated. Induced fermentation had a negative effect (p<0.05) on the coffee's Brix values when compared to spontaneously fermented samples, suggesting greater sugar consumption with the induction. Longer fermentation times affected (p<0.05) the pH of the samples, suggesting an increase in fermentative activity with fermentation time. The treatments did not affect (p<0.05) total phenolic compounds as a whole; however, HPLC analysis revealed higher production (p<0.05) of individual phenolic compounds for the Paraíso cultivar when fermented naturally and for longer periods. Considering final coffee color (post-roast), the longer fermentation time and the Paraíso cultivar exhibited lower (p<0.05) Chroma, likely due to their lower sugar content, resulting in less intense caramelization and Maillard reactions. All coffees showed predominantly positive sensory acceptance, with the highest acceptance obtained for spontaneously fermented coffees with shorter fermentation times and from the Paraíso cultivar. Induced fermentation was associated with the perception of lactic notes in both cultivars, while spontaneous fermentation favored chocolate and caramel notes only for the Paraíso cultivar. The type of fermentation, duration, and cultivar were of great importance in affecting coffee quality, both in physical-chemical and sensory attributes. This work was supported by the Financier of Studies and Projects (FINEP), under Grant/Project Nº 01.25.0242.00.