The color changes in longan flesh drying at different drying air temperatures are shown in Fig. 2. As shown in Fig. 2(a), at low drying air temperatures (60-100qC),L* values increased slowly in the first 180 min of drying and then decreased afterwards. These values decreased as drying air temperature increased. At high drying air temperatures (110-130qC), the L* values decreased quickly after the first 60 min of drying and then decreased. These values also decreased when drying air temperature increased. Fig. 2(b) shows that the a* values increased during drying for all drying air temperatures and increased as drying air temperature increased. As seen in Fig. 2(c), at low temperatures, b* values increased and then decreased with increasing drying time. The b* values increased after 60 min of drying afterwards decreased quickly with increasing drying time at high temperatures. The effect of drying air temperature on the changes of b* values was not obvious. These results in dicate that the browning reaction could occur during drying. The total color difference ('E), chroma and hue angle were calculated using Eqs.(1)-(3). Fig. 2(d)-Fig. 2(f) show the total color difference ('E), chroma and hue angle, respectively. The total color difference increased while hue angle decreased with increasing drying time and drying air temperature. The chroma increased and then decreased with increasing drying time at low temperatures. At high drying air temperatures, the chroma increased after 60 min of drying afterwards decreased quickly with increasing drying time. This study show that characteristics of color changes of longan flesh during drying, which showed tendency
change from yellow to red hues.