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

Official URL: https://dx.doi.org/10.1007/s00289-025-05668-9

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° to 41.45° 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.