Effect of Far-Infrared Assisted Heat Pump Drying on Water Status and Moisture Sorption Isotherm of Squid (Illex illecebrosus) Fillets

The influences of far-infrared assisted heat pump drying on water state and water absorption isotherm of squid were investigated. Squid (Illex illecebrosus) fillets were dried in a heat pump (HP) dryer, alone or assisted with far-infrared radiation (FIR), with the power of 500 and 2000 W, at 50 degrees C and air flow rate of 0.8ms (1). The relaxation time (T(2)) of the low field NMR spectrum presented four peaks indicating four different species (T(2)(A), T(2)(B), T(2)(C) and T(2)(D)) distributed in the squid muscle. The relaxation time (T(2)) changes under three drying treatments followed the same pattern. The peak height of components with T(2)(C) and T(2)(D) drastically decreased with increasing dehydration time, whereas drying did not affect T(2)(A) and T(2)(B). Moreover, the attenuation degree of T(2)(C) or T(2)(D) was the greatest in squids under HP+20FIR treatment followed by HP+5FIR, while the degree of HP only treated samples was the smallest. The sorption data were fitted to ten models, and the Modified Mizrahi model gave better predictions than the other models. Also, both water adsorption and thermogravimetric analysis indicated HP dried squids had higher equilibrium moisture contents followed by HP+5FIR and HP+20FIR.