Performance evaluation of low-temperature operated desiccant wheel integrated heat pump drying system for ponyfish (Leiognathus equula) drying

Abstract

Low-temperature drying is an effective technique for preserving the quality of heat-sensitive products such as fish. Integrating a desiccant wheel and a heat pump, the dryer can function at low temperatures and humidity levels while consuming less energy. This study evaluates the performance of a desiccant wheel integrated heat pump dryer (DW-HPD) for drying ponyfish (Leiognathus equula) at 40 °C, 45 °C, and 50 °C, emphasizing drying kinetics, dryer efficiency, mathematical models, and quality retention. The optimal drying temperature of 50 °C achieved the highest drying rate of 8.18 % wb/h. Increasing the temperature from 40 °C to 50 °C reduced the drying time from 10.5 to 5.5 h. Effective moisture diffusivity ranged from 8.40 × 10⁻¹⁰ to 1.87 × 10⁻⁹ m²/s, with an activation energy of 59.14 kJ/mol. The maximum specific moisture extraction rate (SMER) and specific energy consumption (SEC) were 2.21 kg/kWh and 9.4 kWh/kg at 50 °C, respectively. Rehydration ratio (RR) and water holding capacity (WHC) ranged from 1.172 to 1.183 and 0.336–0.406 g water/g dry solid. Water activity and texture values were 0.740–0.748 and 0.698–0.656 kg, respectively. The Hunter L* value indicated improved color quality, while sensory scores for overall acceptability at 45 °C and 50 °C ranged from "like moderately" to "like very much," confirming the high-quality standards of DW-HPD dried ponyfish.