Optimum conditions of roasting process of Liberica coffee towards the local and international preference

Abstract

Coffea liberica is one of the common coffee species grown in most Southeast Asia countries, especially in Malaysia. However, its production accounts for just 2% globally. In general, coffee beans’ roasting temperature and roasting time are critical factors determining the acceptance of roasted coffee by customers. However, there is still a gap in knowledge on the ideal roasting conditions of Liberica coffee based on the critical parameters. In this research, the central composite design (CCD) was used to assess the roasting time and the temperature in 13 treatments. The temperature ranged from 160 to 220°C and the time ranged from 15 to 30 mins. In the sensory analysis, 30 drinking panellists from local and international countries assessed the coffee brews' acceptability and the sensory attributes considered were colour, aroma, taste, and mouthfeel. By using response surface methodology (RSM), the optimum roasting conditions were determined based on the sensory analysis applied. The colour value of both roasted and ground coffee (p<0.05) was significantly influenced by roasting temperature and time, but only roasting temperature (p<0.05) affected the sensory acceptability of the coffee brew. The optimal roasting conditions were shown to be 197°C for 12.30 mins, corresponding to the roasting characterised by the following colour of the roasted Liberica beans: L* 30.43, a* 11.33 and b* 15.77 respectively. The disparity between Liberica coffee preference by two region panellists was also examined by a two-sample T-test, proving no difference between local and international selection.