Optimization and characterization of active bio-plastic film from tamarind (Tamarindus indica L.) seed starch enriched with red grape pomace extract

Abstract

Active biodegradable films offer a promising solution to the issue of food contamination and loss by providing suitable packaging materials that help maintain food quality and extend shelf life. This study focused on optimizing and characterizing active bio-plastic films made from modified tamarind seed starch enriched with red grape pomace extract. The physical, mechanical, barrier, thermal, antioxidant, and antibacterial qualities of the films were assessed. Using response surface methodology, modified tamarind seed starch (MTSC), glycerol (GC), and red grape pomace extract concentration (RGPEC) were optimized to values of 3.5% w/v, 25% w/w, and 6% w/w, respectively, to develop active bio-plastic film using solvent-casting techniques. The film’s optimal tensile strength was improved significantly (p < 0.05) from 11.87 ± 0.02 MPa for pure tamarind seed starch bio-plastic to 12.77 ± 0.02 MPa for active bio-plastic film, demonstrating improved the mechanical characteristics. When compared to the pure tamarind seed starch-based film, which had a water vapor permeability of 2.4 × 10^–10 ± 0.005 gm⁻¹h⁻¹Pa⁻¹, the optimized film enriched with red grape pomace had a water vapor permeability of 2.35 × 10^–10 ± 0.001 gm⁻¹h⁻¹Pa⁻¹, which was notable (p < 0.05). The grape pomace extract exhibited higher antioxidant activity (IC₅₀ = 280.5 ± 0.042 µg mL⁻¹) compared to the active film (IC₅₀ = 556 ± 0.038 µg mL⁻¹) and non-active film (IC₅₀ = 320067.3 ± 0.024 µg mL⁻¹) in the DPPH assay. The extract also had larger zone of inhibition values against Staphylococcus aureus (10.00 ± 0.01 mm) in contrast to the active bio-plastic film (8.2 ± 0.02 mm). For Escherichia coli, the values were 8.5 ± 0.03 mm for the extract and 7.4 ± 0.05 mm for the active film. In non-active films (film without GPE), no antimicrobial activity was seen. The active bio-plastic film decomposed to about 63% of its original weight after 30 days. Overall, the active film exhibited positive mechanical, barrier, antibacterial, and antioxidant properties compared with pure tamarind seed starch film, making it appropriate for applications in food packaging.