Effect of Pinus radiata extract on the properties and performance of sodium alginate and kappa-carrageenan composite films

Composite films of sodium alginate and kappa carrageenan (SAC) enriched with Pinus radiata bark extract (EnPBE) were fabricated using the casting method. The effects of varying EnPBE concentrations (0.1-1% v/v) on the SAC-based films were comprehensively evaluated. Assessments included surface color measurement, surface hydrophobicity, atomic force microscopy, transparency analysis, barrier properties, X-ray diffraction, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy and antioxidant analysis. Thermal properties were analyzed using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Additionally, in-vitro release studies were performed to study the release behavior of the EnPBE. The findings revealed that increasing the EnPBE concentration led to a notable decrease in the swelling index and film transparency, while thickness, moisture content, water permeation, and flexibility increased. Color analysis revealed a significant increase in the red/green value (a*) and yellow/blue value (b*) of the films, consistent with visual observations. The water contact angle values decreased from 49.06 degrees to 41.45 degrees with the addition of EnPBE. Moreover, the release of the extract in both aqueous and methanolic environments showed a significant increase at higher concentrations. DPPH and ABTS antioxidant assays demonstrated a concentration-dependent increase in the free radical/cation scavenging capacity of the films. The surface roughness of the films increased with the addition of EnPBE, consistent with SEM results that showed particles on the surface of EnPBE-loaded films. TGA and DSC analyses demonstrated improved thermal stability of the films with the incorporation of EnPBE.