Process Modeling and Convective Drying Optimization of Raspberry Pomace as a Fiber-Rich Functional Ingredient: Effect on Techno-Functional and Bioactive Properties

This study aimed to transform raspberry pomace, a by-product of the berry industry, into a sustainable, fiber-rich functional ingredient using convective drying. Drying experiments were conducted at temperatures of 50, 60, 70, 80, and 90 degrees C to identify the optimal conditions that balance process efficiency and preservation of functional and bioactive properties. The best results were achieved at 70 degrees C, where a high drying rate (DR) of 0.46 kg H2O<middle dot>kg-1 db<middle dot>min-1, effective moisture diffusivity (Deff) of 1.53 x 10-10 m2<middle dot>s-1, and activation energy (Ea) of 34.90 kJ<middle dot>mol-1 were observed. The Page model accurately represented the drying behavior (R2 = 0.9965-0.9997). Total dietary fiber (TDF) content remained stable across temperatures (52.52-64.76 g<middle dot>100 g-1 db), while soluble dietary fiber (SDF) increased by 43.40%, resulting in a solubility (SOL) of 71.8%, water-holding capacity (WHC) of 8.2 mL<middle dot>g-1 db, and oil-holding capacity (OHC) of 3.0 mL<middle dot>g-1 db. High retention of bioactive compounds was achieved at 70 degrees C, including phenolics (32.10 mg GAE<middle dot>g-1 db) and anthocyanins (25.84 mg C3G<middle dot>g-1 db), resulting in significant antioxidant activities (DPPH: 33.29 mg AAE<middle dot>g-1 db, IC50 0.016 mg<middle dot>mL-1; ABTS: 35.85 mg AAE<middle dot>g-1 db, IC50 0.029 mg<middle dot>mL-1). These findings demonstrated the potential of convective drying at 70 degrees C to efficiently transform raspberry pomace into a high-quality functional ingredient. This process promotes sustainable production and waste reduction in the berry industry.