Barrier properties characterization and release kinetics study of citrus fibers-reinforced functional starch composites

Abstract

Poor barrier properties and functions have limited the application of starch film in the food industry. This work aimed to explore the effect of different citrus fibers on the starch composite's barrier properties and polyphenols' release kinetics. The pectin and polyphenol contents of the native citrus fiber were 25.58% and 16.63 mg GAE/g, respectively, which were reduced by pectin extraction procedures. Microrheology analysis showed that the incorporation of citrus fibers, especially the 1-grade extracted fiber, improved the viscoelasticity and network structure of the starch aqueous system during film formation. As a result, the microstructures of the developed starch composite were modified, as supported by the compact cross-section structures without cracks, reduced water activity, and increased hydrogen bonding energy (19.13 kJ/mol) revealed by SEM, LF-NMR, and FTIR. Release studies showed that the active films exhibited controlled polyphenol release for up to 24 h in food systems. The release kinetics were well-fitted by Fick diffusion and Peleg models. The barrier properties of the starch composites were improved with citrus fibers, as evidenced by the reduced water vapor permeability (to 3.46 × 10⁻¹⁰ g m⁻¹·s⁻¹·Pa⁻¹), increased anti-ultraviolet property (to 99.29%), and improved tensile strength (to 8.52 MPa). These enhancements were owing to the improved microstructure of the material, and the inherent strength, UV blocking, and physical barrier properties of citrus fiber. This study provided a theoretical basis for the development of a high-performance active starch composite with citrus fibers for food preservation.