Bioactive alginate films with Amazonian extracts: physicochemical performance and real food application in avocado preservation

Abstract

Bioactive extracts from three underutilized Amazonian fruits, Euterpe oleracea (10–50 g·100 g⁻¹ alginate), Myrciaria dubia (10–50 g·100 g⁻¹ alginate), and Theobroma bicolor (10–50 g·100 g⁻¹ alginate), were incorporated into alginate matrices (2% w/v) to produce biodegradable films with enhanced functionality for active food packaging. Extracts were characterized by proximate composition, dietary fiber and metabolomic profiles, revealing distinct phytochemical fingerprints. The composite films displayed extract- and concentration- dependent changes in thickness (0.11–0.32 mm), solubility (38.7–195.3 mim), opacity (1.06–8.76) and color (e.g., L* 23.51–91.37). Barrier performance of the films improved at all concentrations with E. oleracea, but mechanical strength was compromised at 50 g extract·100 g⁻¹ alginate (e.g., 5.59 MPa for Eo50Alg and 8.67 MPa for Eo25Alg). Both M. dubia and T. bicolor showed plasticizing effects (10–50 g extract·100 g⁻¹ alginate), while improving barrier properties at low concentrations (10 g extract·100 g⁻¹ alginate). Additionally, M. dubia imparted antimicrobial activity on Gram-positive bacteria (50 g extract·100 g⁻¹ alginate). FTIR confirmed crosslinking between alginate and all fruit extracts, predominantly as phenolic-alginate intermolecular hydrogen bonds. TGA indicated improved thermal stability, particularly for E. oleracea films (residual mass ∼30%). In a real-food model using avocado pulp, all composite films delayed oxidative degradation (up to 80% with E. oleracea), improved pigment retention (T. bicolor) compared to neat alginate films (p < 0.05). Our results demonstrated the potential of Amazonian fruits as a clean source of functional additives for the formulation of active bioplastics that preserve the quality of high-value foods over storage.