Production of functional Arabica and Robusta green coffee beans: Optimization of fermentation with microbial cocktails to improve antioxidant activity and metabolomic profiles

Currently, growing recognition of the health benefits associated with functional foods and bev-erages has increased the demand for products that offer more than just basic nutrition. Coffee is a widely consumed beverage, in which fermentation of green coffee beans contributes to the development of a special aroma and higher levels of antioxidants. The objectives of this study were to optimize the fermentation conditions and simultaneously improve antioxidant activity and metabolites. The conditions optimized by Box-Behnken design (BBD) suggested that the highest total esters, total phenolic content (TPC), and antioxidant activity (ABTS, DPPH, FRAP) could be reached by fermentation at 30 degrees C for 2 days with 13.25% sucrose (w/w) using a mi-crobial cocktail. Two sets of selective microbial starters, Lactiplantibacillus plantarum TISTR 2265 (LP) and a cocktail of TISTR yeasts with LP (YC-LP), were further considered as powerful starters for solid-state fermentation (SSF) of Arabica and Robusta beans, enhancing antioxidant activity within the first 3 days of fermentation. Arabica beans fermented by LP reached 198.03% TPC, 44.21% ABTS, 90.35% DPPH, and 97.13% FRAP, while Robusta beans fermented by YC-LP showed 108.24% TPC, 204.19% ABTS, 170.71% DPPH, and 59.60% FRAP, higher than an un-inoculated starter. The analysis of 41 fermented metabolites revealed the different metabolomic profiles for both coffee beans, offering valuable insight into the correlation between chemical constituents and functional characteristics. This study represents the first comprehensive com-parison of the metabolomic profiles of fermented Arabica and Robusta green coffee beans.