20℃(3.5 h)→25℃(3.5 h)→30℃(3.5 h)→35℃(3.5 h)。Horse mackerels were dried in a heat pump dehumidifier (HPD) which is capable of producing stepwise control of drying air temperature. Two stepwise air temperature profiles were tested. The drying characteristics and total color difference (ΔE) of the products dried under these stepwise variation of temperature were measured and compared with constant air temperature drying. It was observed that by employing stepwise change in drying air temperature with the appropriate starting temperature and cycle time, it was possible to reduce drying time to reach the desired moisture content with significantly improved product color. The optimum condition for time-varying temperature drying of horse mackerel was step-up profile with initial temperature of 20℃ and cycle time of 3.5 h. 