Active films produced using ginger oleoresin nanoemulsion: Characterization and application on mozzarella cheese

Ginger oleoresins contain bioactive phenolic compounds that are more storage-stable but less studied than the volatile oil fraction. This study aimed to produce a stable nanoemulsion from ginger oleoresin to use as an active material for food application. Ginger coarse emulsion (GCE) was prepared by high-shear homogenization (7000 rpm). Nanoemulsions also used ultrasound (power 750 W) at 20 %, 30 %, or 45 % of amplitude for 1, 3, or 9 min. The optimized nanoemulsion (GEN) (average particle size 105 nm, Zeta potential −18 mV) showed stability for at least 56 days stored at 4 or 20 °C, while GCE precipitated within 7 days. GEN showed an antimicrobial effect against S. aureus and E. coli. GEN was incorporated into a gelatin hydrogel (1.50 % and 0.75 % oleoresin), and active films were obtained by casting. The films were applied as slice separators for mozzarella and stored at 4 °C to control the oleoresin release to cheese slices. Oleoresin migration to the food surface, color, pH, weight loss, visual mold formation, and colony growth were monitored over 56 days. Nanoemulsion acted as a plasticizer, increasing films' elongation (31–71 %) and reducing tensile strength (35-20 MPa). Oleoresin blocked 200–400 nm wavelength radiation. The films exhibited high barriers against CO₂ (4.8–6.3 × 10⁻⁹ mol μm/m₂·Pa·s) and O₂ (4.8–6.5 × 10⁻⁹ mol μm/m²·Pa·s), and low barrier against water vapor (0.43–0.47 g mm/h·m²·Pa). Oleoresin was released from the films for at least 56 days, increasing the media's antioxidant activity to 624 mg. Trolox/mL and delaying the visual mold incidence in sliced mozzarella cheese from 28 to 42 days.