Valorization and application of coffee husks extracts in cassava starch-based biodegradable packaging

Abstract

The growing demand for sustainable packaging with functional properties has encouraged the development of polymeric films incorporating bioactive compounds and the valorization of agro-industrial residues. In this study, active cassava starch-based films were produced (FC – without extract) and compared to films containing coffee husk extract at concentrations of 0.5 % (F5) and 0.75 % (F75). The aim of this work was to evaluate the effects of incorporating these compounds on the physical, thermal, mechanical, optical, and functional properties of the polymeric matrix. The Scanning Electron Microscopy (SEM) images revealed homogeneous surfaces with good extract dispersion, corroborated by elemental composition via Energy Dispersive X-ray Spectroscopy (EDS). Thermogravimetry (TGA) and Differential Scanning Calorimetry (DSC) analyses indicated higher stability, with degradation temperatures exceeding 300 °C. Regarding mechanical properties, tensile strength increased from 10.31 MPa (FC) to 66.06 MPa (F75). Elongation at break also increased significantly in the extract-containing films, rising from 0.27 % (FC), characteristic of a rigid material, to 2.67 % (F5) and 3.28 % (F75), suggesting a plasticizing effect. The control film exhibited low absorption in the UV–Vis range, whereas the incorporation of the extract significantly increased absorption, improving UV-blocking capacity. Extract-enriched films demonstrated significant antioxidant activity, with values of F75 of 15.9 % (2,2-difenil-1-picril-hidrazil – DPPH), 44.3 % (2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) - ABTS), 25.1 μmol Trolox/g (Ferric Reducing Antioxidant Power - FRAP), and 53.7 mg GAE/g (Total Phenolic Content - TPC). Additionally, oxidative stability was assessed using the Rancimat method, where the film containing 0.75 % extract (F75) significantly increased the induction period of soybean oil compared to the control, confirming the protective effect of coffee husk phenolics against lipid peroxidation. Therefore, the incorporation of coffee husk extract provided the films with multifunctional enhancements, reflected in improved structural, mechanical, optical, and functional properties, reinforcing their applicability as a viable and sustainable alternative for active packaging.