Physicochemical properties and sensory quality of Motlopi (Boscia albitrunca) coffee prepared using different temperature-time combinations

Motlopi coffee is a beverage prepared from roots of an indigenous tree Boscia albitrunca and consumed in Botswana. To date, there is no published report about the quality characteristics of Motlopi coffee. This study was conducted to develop an improved Motlopi coffee by varying roasting time and temperature and assess its physicochemical properties and sensory quality. The roasting temperatures considered were 150 °C and 160 °C with roasting time of 10, 15 and 20 min at each temperature. The study showed that bulk density of ground coffee was significantly (p < 0.05) decreased at 160 °C than at 150 °C and pH of Motlopi coffee was generally higher at 150 °C than at 160 °C. The total soluble solids (TSS) of Motlopi coffee decreased with increasing roasting time at 150 °C; however, it increased with increase in roasting time at 160 °C. Browning index (BI) tended to increase with increase in roasting time both at 150 and 160 °C and was significantly (p < 0.05) higher at 160 °C than at 150 °C. The titratable acidity (TA) decreased with an increase in the roasting time both at 150 and 160 °C and was significantly (p < 0.05) higher at 150 °C than at 160 °C. The traditionally prepared Motlopi coffee had comparable TA with treatment 2 (150 °C for 15 min). The consumer acceptability test showed that the laboratory made Motlopi coffee had significantly higher (p < 0.05) scores for taste, body and overall acceptability than the traditional Motlopi coffee. Roasting Motlopi roots at 150 °C for 15 min resulted in Motlopi coffee of good physicochemical properties and sensory quality.