Spray‑drying microencapsulation of tomato pomace extract using enzymatically modified protein carriers for improved stability, controlled bioactive accessibility, and application in functional sponge cake

Tomato pomace, a major by-product of tomato processing, is a rich source of lycopene and phenolic antioxidants; however, direct incorporation into foods is limited by instability and potential sensory impacts. This study investigated spray‑dried microencapsulation of tomato pomace extract (TPE) using gelatin (GEL) and corn pollen protein (CPP) and their enzymatically hydrolyzed forms (HGEL and HCPP), and evaluated the resulting powders for sponge cake fortification. Particle morphology, structural interactions, color properties, and thermal stability were assessed by SEM, FT‑IR, color analysis, and TGA/DSC. Microcapsule morphology varied with carrier type: GEL showed partially collapsed and agglomerated structures, whereas HGEL produced smaller, more spherical particles with smoother shells. Encapsulation improved thermal stability, increasing the degradation onset temperature from 179.2°C (TPE) to 308.5°C (HGEL). Lycopene and total phenolics in powders ranged from 155-235µg/g and 1.50-2.75mg GAE/g DM, respectively. In cake application, neat TPE reduced volume (58.5cm³ in control to 51.0cm³ at 6%) and increased crumb firmness (1.05 to 1.82N), while HGEL cakes better preserved structure (firmness 1.22-1.44N) with minimal color change (ΔE≈1.85-2.05). Fortification increased total phenolics from 0.26mg GAE/gDM (control) to 2.49mg GAE/gDM (TPE‑6) and 2.35mg GAE/gDM (HGEL‑6), and DPPH activity from 20.92% to 58.25% and 54.83%, respectively. Sensory evaluation by a semi-trained panel indicated reduced acceptability for TPE‑6 (taste/odor=2.50), whereas HGEL‑3 remained close to the control (4.40). Overall, the results indicate that the carrier type and resulting particle morphology are associated with differences in apparent bioactive extractability, thermal stability, and performance in a thermally processed bakery matrix, with HGEL showing the most favorable balance.