University of Coimbra, Coimbra, Portugal
An increasing interest in food packaging materials without environmental impact has emerged in the last decade. Those materials are biodegradable and renewable biopolymers such as chitosan and cellulose, which can be obtained from fishing and agroforestry wastes, respectively, making them very attractive resources in the biorefinery context. Moreover, in the food packaging sector, there is a need to increase food shelf -life and reduce the use of petroleum derivatives. Therefore, the aim of this work was to improve chitosan derivative-based films with a reinforcing material (cellulose), a plasticizer (silicone) and/or pine extract loading, as antioxidant agent.
N-carboxybutylchitosan films were produced and the inclusion of cellulose and aqueous extract from pine stumps were tested. The effect of silicone (Silpuran® 2130 A/B) was assessed. Biofilms were characterized: thickness, color, thermogravimetry, water contact angle, mechanical properties, and antioxidant activity (DPPH).
Films showed thickness of 55 - 63 µm, with the higher values corresponding to the extract-loaded films. Contact angles ranged from 84 to 102°, and the addition of cellulose and silicone increased the hydrophobicity. For the extract-loaded films, significant color difference and some opacity were observed. Films degradation occurred at ~ 300 °C, and Young's modulus for N-carboxybutylchitosan-cellulose-silicone-extract films was ~ 76 ± 16 MPa. Both silicone and pine extract reduced the maximum tensile strength to values < 35 MPa, while a high antioxidant activity was revealed by the extract (IC50 ~ 6 µg/mL).
Films loaded with the antioxidant extract have potential to increase food shelf-life and decrease photo-oxidation. Further investigations related to plasticizers are ongoing to increase film flexibility.