Carbohydrate Enrichment in In-Vitro Civet Coffee Fermentation: Impact on Arabica Coffee Beans

Abstract

This study aimed to evaluate the performance of in-vitro fermentation processes on civet coffee, employing a mixed-microbial enrichment culture, and to assess its impact on the physicochemical properties of the fermented product. Arabica Coffee cherries were utilized as the subject in this investigation. The inoculum, derived from civet fecal suspensions, was enriched through the augmentation of various carbohydrates, including soluble (e.g., glucose) and insoluble (e.g., starch) carbohydrates, mirroring the primary components present in civet food. Over an incubation period of four hours, a drop in pH from 7.0 to 5.6 was observed in the cultures, and volatile fatty acid (VFA) was detected at 2.8 mmol/L. It was found that the sugar conversion rate during in-vitro coffee fermentation by the starch-consuming microbial culture (2.1 mM/hour) significantly outperformed that of the glucose-consuming culture (0.9 mM/hour). The caffeine content in in-vitro fermented coffee (0.27-0.28 mg/100g) was found to closely approximate that of in-vivo fermented coffee via civet digestion (0.254 mg/100g). Notably, both in-vitro and in-vivo fermentation yielded caffeine content substantially lower than that of conventionally fermented coffee, which ranged between 1.5 and 2.7 g/100 g. In summary, the fermentation of Arabica coffee cherries using a mixed microbial culture, enriched with starch supplementation (SCM), demonstrated a faster rate compared to a culture enriched with glucose (GCM). The findings provide important insights for optimizing invitro civet coffee fermentation processes.