As a whole, the DE of BSS increased significantly during FD and HAD with different temperatures. The DE valued 4.73 using with FD, lowest level among all drying methods. However, the DE increased from 14.30 to 19.82 using HAD with the temperature increasing from 50 °C to 90 °C. This demonstrated that FD exerted far less influence on the colour change in BSS compared with HAD. Therefore, from these results, it can be understood that some modifications would have occurred in the optical properties of BSS during FD and HAD, which may not be accepted by the consumer. Similar result had been reported by Bal et al. (2011) through their microwave-drying research on BSS.