This study presents a comprehensive evaluation of starch-based gel formulations enriched with proteins and hydrocolloids for extrusion-based 3D food printing (3DFP). Food inks were prepared using corn or potato starch, protein concentrates (fava, whey, rice, pea and soya), and hydrocolloids (κ-carrageenan, arabic gum, xanthan gum, and carboxy methylcellulose). Their rheological, mechanical, and textural properties were systematically analyzed to assess printability. Among all formulations, those containing κ-carrageenan consistently demonstrated superior viscoelastic behavior (G′ > 4000 Pa), optimal tan δ values (0.096–0.169), and yield stress conducive to stable extrusion. These inks also achieved high structural fidelity (93–96% accuracy) and favourable textural attributes such as increased hardness and chewiness. Computational Fluid Dynamics (CFD) simulations further validated the inks’ performances by linking pressure and velocity profiles with rheological parameters. FTIR analysis revealed that gel strengthening was primarily driven by non-covalent interactions, such as hydrogen bonding and electrostatic effects. The integration of empirical measurements and simulation provided a robust framework for evaluating and optimizing printable food gels. These findings contribute to the advancement of personalized and functional 3D-printed foods through data-driven formulation design.

Olive oil production generates large amounts of agricultural and agro-industrial residues, with olive leaves representing one of the most abundant by-products. This study investigated the valorization of olive leaves from two Greek cultivars, Koroneiki and Megaritiki, collected from the Aeghion, Heraklion, and Megara regions, by means of an optimized green extraction process for the effective recovery of phenolic compounds. Response surface methodology (RSM) was applied to optimize solvent composition and extraction time using ethanol/water mixtures (0/100, 30/70, 50/50, and 70/30, v/v) and extraction times ranging from 15 to 90 min. Total phenolic content (TPC), antioxidant activity (DPPH and FRAP), and color parameters were determined spectrophotometrically, while individual phenolic compounds were analyzed by HPLC-DAD. Both solvent composition and extraction time significantly affected phenolic recovery and antioxidant activity. The optimal extraction conditions were 37.5/62.5 (v/v) ethanol/water and 52.5 min. Extracts from Megara showed the highest TPC (32 ± 1 g GAE kg⁻¹ LL), antioxidant capacity (2556 ± 162 mmol Trolox kg⁻¹ LL), and phenolic compound levels. Significant differences were observed between the two cultivars, whereas Koroneiki samples from Heraklion and Aeghion exhibited similar phenolic profiles, indicating that cultivars had a greater influence than geographical origin.