Comparative evaluation of biocomposite films based on pea protein and cottonseed protein: Impact of microcrystalline cellulose concentration on their performances

Abstract

The environmental and health impact of petroleum-derived synthetic plastics has increased the demand for renewable and biodegradable food packaging materials To meet this requirement, biocomposite films were carefully made using either hydrophilic pea protein (PP) or hydrophobic cottonseed protein (CSP) matrices. The proportions of microcrystalline cellulose (MCC) were gradually increased at 0%, 1%, 3%, and 5% w/w to observe their effects. The physical, mechanical, and barrier properties of the produced films were compared. The results demonstrated that a 3% (w/w) MCC ratio was optimal for inclusion in both protein matrices. Incorporating 3% (w/w) MCC increased the tensile strength (TS) to 17.68 MPa for PP and 8.24 MPa for CSP, due to the uniform distribution of crystalline cellulose particles within the polymer matrix. Additionally, thanks to the physical barriers to fracture within the matrix (the circuitous path effect), water vapor permeability (WVP) was reduced to 0.31 and 0.21 g·mm/m²·h·kPa, respectively, achieving maximum water resistance. In a 30-day oxidation test using sunflower oil as a real-food simulant, the CSP-3 film demonstrated an excellent oxygen barrier, keeping the peroxide value (PV) (5.80 meq O₂/kg) at its minimum. This effectiveness results from the hydrophobic properties of cottonseed protein combined with the synergistic interaction of MCC. Conversely, at a 5% (w/w) concentration of MCC, minor reductions in barrier efficacy were observed, presumably due to aggregation and phase separation. In summary, evaluating MCC with CSP (an industrial byproduct) reveals it as a great sustainable alternative for bio-packaging, providing strong mechanical properties and notable resistance to oxidation.