Biodegradable trays of cassava starch reinforced with Ceiba, coffee and cocoa fibers: a sustainable alternative to plastics

The growing interest in natural substitutes for polystyrene in packaging development has directed attention to plant residues such as ceiba (Ceiba trischistandra), coffee (Coffea arabica) and cocoa (Theobroma cacao). The objective of this study was to develop biodegradable trays using cassava starch as a base matrix and to reinforce them with different proportions of ceiba, coffee and cocoa fiber. The trays were thermoformed at 150 °C, 60 bar and 10 min. Physicochemical analyses revealed that a higher fiber content significantly modified color, thickness, density, moisture and water activity. In relation to mechanical properties, it was observed that a higher proportion of fiber improved textural properties. Trays with Ceiba fibers presented the highest fracturability (40 N), while those with cocoa fibers showed higher mechanical strength (0.4 MPa). Differential scanning calorimetry analysis showed that the trays with cocoa fibers had the highest melting point (192.51 °C), which gives them greater thermal stability. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) studies revealed a positive interaction between the starch matrix and the fibers, which favored the cohesion and stability of the material. Finally, biodegradability tests showed that the trays experienced progressive degradation under controlled conditions of high humidity, with significant structural loss after 32 days of exposure. These results confirm that the addition of fibers improves the mechanical and thermal properties of the material, which broadens its potential application as a biodegradable packaging for products with low water activity, such as nuts or bakery products.