Phytochemical fortified casein, soy and zein-based bioactive packaging films with antimicrobial and antioxidant properties

This study aimed to develop and characterize protein-based bioactive packaging films fortified with colored corn-derived phytochemicals under varying pH conditions (pH 3 and 9). Films were formulated using soy, zein, and casein proteins, with and without phytochemical extracts. Ultrasonication and heat-induced stirring ensured uniform protein denaturation, followed by casting at 35 °C for 24 hours. Corresponding mechanical, antioxidant, antimicrobial, UV barrier, physicochemical properties, thermal properties and water vapor permeability were evaluated. Soy and zein protein-based films incorporating phytochemicals (SAE and ZOE) exhibited complete inhibition of Bacillus subtilis and Escherichia coli . Casein-based film (CAE) containing phytochemicals demonstrated a fivefold increase in antioxidant activity (119.39 mg TE/g film) compared to control (19.38 mg TE/g film). All bioactive films displayed near-zero UV transmittance, confirming effective UV barrier/photoprotective properties. The tensile strength of casein-based films (CA and CB) was 2.72 and 3.19 MPa with higher elongation at break percentages of 95.65 and 102.67%, respectively. Zein-based film (ZOE) had the highest tensile strength of 4.08 MPa but the least elongation at break percentage of 13.72%. Most films were thermally stable, with casein-based films showing endothermic peaks at 255.98 °C. Zein-based films with phytochemicals demonstrated the lowest water vapor permeability (0.59 × 10⁻¹⁰ g/Pa·s·m), indicating improved moisture barrier properties. All films were compatible with laser engraving. Films developed under acidic conditions consistently demonstrated enhanced antimicrobial efficacy compared to those produced under basic conditions. Protein-based and colored corn phytochemical fortified bioactive films, especially those formulated under acidic conditions exhibited superior antimicrobial, antioxidant, and barrier properties.