Volatile Compounds Changes in Unfermented Robusta Coffee by Re-Fermentation Using Commercial Kefir

Robusta coffee usually has a low quality because the formation of flavored precursors is imperfect. The efforts to form a flavored precursor of unfermented Robusta coffee can be done by re-fermenting the coffee using reproduction which is able to help the formation of flavored precursors such as lactic acid bacteria found in kefir. The appropriate temperature condition and time period are needed to be considered in re-fermenting the unfermented Robusta coffee. This study aimed to determine the effect of temperature and time on the volatile compound’s changes in unfermented Robusta coffee by commercial kefir. This study used two factors, including temperature (27, 37 and 47 ℃) and re-fermentation time (6, 12 and 18 hours). The results showed that duration and temperature of re-fermenting could improve the aroma characteristics and volatile compounds. Re-fermentation of Robusta coffee bean can increase total of volatile compounds at 37 ℃ for 18 hours. The increasing volatile compounds of acid, alcohol, aldehyde and acetate groups contributed to give the pleasant aroma as follows acidy, fruity, nutty and caramelly aroma.