Concentration-Driven Modification of Agar-Based Biodegradable Films Using Carpobrotus Glaucescens Phytochemical Extract

Abstract Agar-based films are promising biodegradable materials, but their brittleness and moisture sensitivity limit practical use. In this study, a phytochemical extract from the Australian halophyte pigface ( Carpobrotus glaucescens ) was evaluated as a concentration-dependent modifier of agar films. CHNS, FTIR, ¹H NMR and untargeted LC-MS established a chemically complex, hydroxyl-rich composition; these analyses provide a baseline compositional context but do not directly demonstrate a specific agar-extract bonding mechanism. Across the formulation-screening matrix, P6 (agar-to-extract ratio, A:PF = 1:20, w/v) showed a 38% increase in tensile strength and an elongation at break of approximately 23% relative to the control, while water vapour permeability decreased from 2.91 × 10⁻¹¹ to 1.26 × 10⁻¹¹ g/m²·s·Pa ( p < 0.05). These property changes coincided with qualitative changes in film FTIR profiles, surface morphology, apparent glass-transition behaviour and drying kinetics; however, the independent contributions of agar and extract could not be isolated because both concentrations varied in the screening design. At higher extract loading, P9 (A: PF = 1:40, w/v) showed particulate surface heterogeneity and lower mechanical performance. Antioxidant activity was retained, with total phenolic content reaching 28.0 mg GAE/g. The selected intermediate films remained hydrophilic, and all formulations were highly water-soluble. The results identify a favourable intermediate formulation window for exploratory short-term, low-moisture or non-food biodegradable applications. Food-contact or edible use would require improved water resistance, arsenic speciation, migration testing and toxicological assessment.