Effect of Hot-Air Drying Temperature on the Physicochemical, Functional, Compositional, and Structural Properties of Catfish (Clarias macrocephalus × C. gariepinus) Powder

Catfish (Clarias macrocephalus × C. gariepinus) is economically important but perishable, and hot-air drying yields shelf-stable catfish powder (CFP); however, its quality response to high-temperature drying (>100 °C) remains poorly understood. The present study aimed to examine the effects of five drying temperatures (60–180 °C) on the physicochemical, nutritional, functional, structural, volatile, oxidative, and microbiological properties of CFP. Drying exerted parameter-specific effects. Moisture and water activity fell from 6.24% to 4.75% and 0.42 to 0.23, with microbial counts reduced at ≥120 °C. Browning raised lightness, redness, and yellowness from 49.53 to 57.64, 1.94 to 2.97, and 13.95 to 18.14, respectively. Protein concentrated from 57.63% to 62.24%, whereas oxidation lowered fat from 22.49% to 17.17%. Minerals rose marginally, although iron and zinc declined. Amino acids were largely preserved, though methionine (2.71 to 2.21 g/100 g protein) and cysteine declined and glycine and proline increased. DHA declined most, from 4.61% to 3.20%, followed by EPA and AA. Water holding, oil holding, wettability, dispersibility, and colloidal stability decreased, whereas emulsion stability decreased from 57.14% at 60 °C to 42.10% at 180 °C. Zeta potential became less negative (−35.82 to −20.74 mV), with larger particle size and polydispersity. Among 72 volatiles across 11 classes, 60–90 °C favored fishy aldehydes and 2-pentyl furan and ≥150 °C generated Maillard and sulfur compounds, whereas 120 °C produced the most balanced volatile profile, with lower relative abundance of fishy aldehydes than at 60–90 °C, consistent with the intermediate TBARS values and comparatively better retention of unsaturated fatty acids at this temperature, and limited accumulation of Maillard-derived and sulfur compounds relative to 150–180 °C. FTIR, XRD, TGA, and SEM confirmed preserved structure. Overall, the results showed that 120 °C provided the best balance of dehydration, nutrient and functional retention, flavor, and microbial safety.