Extraction-Induced Molecular Balance Governs the Film-Forming and Emulsion-Stabilizing Performance of Yellow Passion-Fruit-Peel Mucilage Pectins

Five pectin-rich mucilage fractions from yellow passion-fruit peel, extracted using 0–10.0% (w/v) citric acid, were evaluated in separate films and sunflower-oil emulsions. The 0.086% fraction gave the highest mean tensile strength and Young’s modulus (31.26 and 468.9 MPa), while 0.086–0.50% produced the lowest water-vapor permeability (1.70–1.82 × 10−10 g m m−2 s−1 Pa−1). The 0.50% fraction produced the smallest initial and day 21 emulsion droplets (1.72 and 1.81 µm) and the lowest day 21 creaming (2.0%). At 10.0% acid, film strength decreased to 3.34 MPa, while emulsion droplets reached 5.31 µm and creaming reached 28.1%, despite the most negative ζ-potential (−56.0 mV). These responses are consistent with reduced molecular integrity under severe extraction and indicate that charge alone does not determine performance. Under the tested formulations, mild extraction at 0.086–0.50% citric acid provided the most favorable combination of film and emulsion properties.