Sustainable active poly(Lactic acid) films reinforced with pea pod ethanolic extract: Structure-property relationships and functional performance

In this study, polyphenolic extract from pea pod extract (PPE) from Pisum sativum was valorized as a natural functional additive in a poly (lactic acid) (PLA) matrix intended for food-packaging applications. PLA-based films containing 5 and 10 wt.% PPE were prepared by the solvent casting method and characterized in terms of chemical structure, crystallinity, morphology, thermal behavior, mechanical properties, wettability, and antioxidant activity. FTIR analysis confirmed the PPE addition into the PLA matrix, with spectral features suggesting possible interactions between PPE and PLA. XRD and DSC analyses showed that PPE influenced the PLA crystalline organization and may have promoted its crystallization. Thermogravimetric analysis showed that the added PPE caused only a slight decrease in thermal stability, with the main degradation of both PLA/PPE formulations occurring above 300°C. SEM observations revealed a relatively homogeneous morphology for PLA/PPE5 and the appearance of micro-voids at higher PPE loading, whereas contact angle measurements indicated an increased surface wettability. Mechanical testing showed a decrease in tensile strength and Young’s modulus, accompanied by increased elongation at break, indicating that PPE modified the PLA film mechanical behavior. Overall, the added PPE modified the structural, mechanical, optical, and antioxidant properties of PLA-based films while providing a sustainable approach to pea pod by-product valorization. The resulting films could represent promising candidates for further investigation in food-packaging applications.