REDUCING SUGAR EXTRACTION FROM OVER-ROASTED COFFEE BEANS AND COFFEE SILVERSKINS

Significant amounts of waste are generated by the coffee industry, among them, coffee
silverskin (CS) and over-roasted coffee beans (OCB) are the most abundantly generated
during the beans roasting. In this study, this material was proximately analyzed and
subsequently submitted to an acid hydrolysis aiming to extract reducing sugar. Reactions
were performed to verify the effects of the variables H2SO4 concentration, temperature, and
reaction time, on the efficiency of hydrolysis. After acid treatment, the hydrolysate was
adjusted to the appropriate pH using sodium hydroxide solution. The conditions that gave a
significant highest amount of reducing sugar were 90°C, 5% H2SO4, and 3 hours, which
yielded 14.570.23 g sugar/L for OCB and 8.370.20 g sugar/L for CS. Treatment the
material at 70°C for either 1 hour or 3 hours gave no significantly different amount of
reducing sugar obtained for both CS and OCB, especially at 1% to 3% H2SO4. The
hydrolysate from acid treatment of OCB and CS can be used as substrate