Physical and Chemical Characteristics of Robusta Coffee Beans Fermented by Kefir Using the Controlled Semi-Carbonic Maceration Method

<ns3:p>Introduction The quality of robusta coffee beans (Coffea canephora var. Robusta) can be modulated by using a specific fermentation method. Fermentation is an important process in coffee bean processing because it greatly determines the final quality of coffee beans, especially their taste. A starter culture is one way to perform a particular process of fermentation. Methods In this study, fermentation was carried out at different temperatures (35°C and 40°C) and times (24 h and 48 h) using kefir as a specific starter culture and the Controlled Semi-Carbonic Maceration Method. Research parameters are: population number of lactic acid bacteria, caffeine content, reducing sugar content, pH, lightness value, the density, and titrated acid value. Results The results of this study indicate that the lactic acid bacteria population showed optimum growth at 24 h of fermentation, which was around 7.67-7.72 log10 cfu/mL. Changes in the chemical and physical characteristics of Robusta coffee beans fermented with a kefir starter were that the caffeine content decreased from 1.41% to 0.46%, the reducing sugar content decreased from 2.42% to 0.29%, the pH decreased from 6.12 to 4.43, the lightness value decreased from 41.68 to 30.54, and the density decreased from 0.50 g/mL to 0.39 g/mL. Still, the total titrated acid value increased from 0.40% to 0.99%. Conclusion This indicates that the addition of kefir as a starter in semi-carbonic coffee fermentation maceration has been successful, as evidenced by the results of data in the form of a decrease in caffeine, reducing sugar, pH, and a decrease in density and lightness. Meanwhile, the total titrated acid increased.</ns3:p>