Development of biodegradable trays from by-products of orange processing

Food packaging is essential to protect products and extend their shelf life. Synthetic plastics of petrochemical origin are still the most widely used; however, they are neither renewable nor biodegradable, contributing to environmental impacts. In this context, bio-based materials are promising alternatives. These can be obtained from by-products of fruit processing, such as orange, which contain compounds capable of exerting active functions, representing a functional advantage compared to conventional materials. Brazil is the world’s largest producer of oranges and the leading exporter of orange juice. The by-products generated during fruit processing are considered non-edible; therefore, the best strategy in these cases is to recover the resource for other purposes. This study proposes the development of semi-rigid materials based on orange juice processing by-products (peel and bagasse) combined with corn starch as a biopolymer. The trays were produced by thermo-pressing using the industrial proportion of peel and bagasse, varying the total concentration of these residues at 0%, 5%, 15%, and 25%, with proportional reduction of starch. Preliminary tests were carried out to identify possible chemical interactions among components using Fourier Transform Infrared Spectroscopy (FTIR), to analyze the microstructure of the trays using Scanning Electron Microscopy (SEM), and to evaluate the effect of residue concentration on color. FTIR analyses showed similar spectra among all trays, possibly due to the starch matrix common to the formulations. The main bands observed were at 3300 cm⁻¹ (O–H, associated with hydroxyls and hydrogen bonds), 2920–2850 cm⁻¹ (C–H from organic chains), and 1200–900 cm⁻¹ (C–O/C–O–C from polysaccharides), characteristic of predominant functional groups. SEM observations revealed porous structures analogous to expanded polystyrene (EPS), but with irregular cavities resulting from the release of water and volatiles during thermo-pressing and degassing. Color tests indicated a reduction in brightness and a shift in hue toward yellow–orange tones with increasing residue concentration, while chroma remained practically constant, indicating matrix saturation. The results confirm the incorporation of residues into the starch matrix and the formation of a structure similar to EPS, reinforcing the potential of the formulation. However, further studies are required to assess mechanical properties, solubility, and biodegradability.