DEVELOPMENT AND CHARACTERIZATION OF NADES-CONTAINING STARCH/ALGINATE COMPOSITE FILMS INCORPORATING GRAPE POMACE FOR INTELLIGENT FOOD PACKAGING

This study evaluated the incorporation of grape pomace powder or Natural Deep Eutectic Solvent (NADES) extract into starch/alginate films. Grape pomace powder (<100 mesh) and heat-modified cassava starch (130°C, 4 h) were used. NADES was prepared by mixing choline chloride and glycerol (1:2 molar ratio) (80°C, 40 min) and then diluted with 30% (v/v) distilled water. Three film formulations were prepared from 4% (w/w) modified starch and sodium alginate blend (5:1, w/w): (i) a control film containing 2% (w/w) NADES as a plasticizer (Control); (ii) a film containing 2% (w/w) NADES and 1% (w/w) grape pomace powder (Powder-film); and (iii) a film containing grape pomace extract obtained using NADES at 0.08 g/mL (Extract-film). All films had thicknesses of 0.13–0.16 mm. The Extract-film showed higher tensile strength (7 ± 1 MPa) than the others (6 ± 1 MPa), whereas the Powder-film was more flexible, with 30 ± 4% elongation at break versus 12 ± 3% for the other films, due to its higher content of plasticizing sugars and anthocyanins. Moisture contents and water solubility values were 11 ± 2, 12 ± 1, and 14 ± 1% and 34 ± 3, 41 ± 2, and 39 ± 6%, respectively, for the Control, Powder, and Extract films, indicating a greater contribution of hydrophilic compounds from grape pomace and NADES. After 60 days, the Powder film showed lower ΔE values than the Extract-film at -18°C (3.8 ± 0.4 vs. 7.8 ± 0.2) and both remained stable at 4°C (1.6 ± 0.3 and 2.9 ± 0.1, respectively). Storage at 25°C increased ΔE in the Powder (18 ± 2) and Extract (6 ± 1) films, while both showed halochromic behavior (pH 4-9), with a marked color change at pH 8 (ΔE > 20) that persisted after 60 days. Both films maintained good color variation at pH 8 after storage, especially the Powder-film. NADES acted as a plasticizer and may favor anthocyanin stabilization through hydrogen bonding. Combining NADES extraction with starch/alginate matrices offers a novel green approach for intelligent packaging.