A top-down approach to improve collagen film's performance: The comparisons of macro, micro and nano sized fibers.

The severe reduction of mechanical strength of collagen once it is extracted or dissociated from animal tissues and no additional crosslinking approaches are conducted, impede its application in biodegradable and edible food packaging. Here, for the first time, high pressure homogenization (HPH) was used to prepare diverse sized fibers and the related fibers-composed films' performance were investigated. These fibers have a diversity of effects on film performance. The films prepared with smaller sized fibers had a more uniform and denser structure. The mechanical and the water barrier properties of the films improved significantly as the fiber size decreased. No obvious change in FTIR and thermal properties suggests that the improved film performance is mainly attributed to the physical entanglement and non-covalent bonds. Given the forementioned benefits of the films, control of fiber size can be a potential industrial approach for producing collagenous materials in edible food packaging.

Metal ions increase mechanical strength and barrier properties of collagen-sodium polyacrylate composite films.

From the previous experiment, it was confirmed that the incorporation of 0.3 wt% sodium polyacrylate (PAAS) into collagen (Co) fibers can improve the mechanical properties and thermal stability of the composite films. In this study, Ca2+, Fe3+ and Ag+ ranging 0.001-0.004 mol/g were used to improve the properties of Co-PAAS blend films based on the rationale of their potential electrostatic interaction with these biopolymers. As expected, Zeta-potential film-forming solutions was decreased to some extent with the addition of metal ions. SEM images presented that the surface of the composites became coarser and internal structure became more stratified as metal ion contents increased. Tensile strength was increased by the addition of these ions with a varied optimal concentration: Ca2+ (0.003 mol/g), Fe3+ (0.002 mol/g) and Ag+ (0.001 mol/g). Water vapor permeability (WVP), solubility and light transmission value of films while causing film thickness no obvious change. In addition, the differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA) results indicated that the metal ions improved the thermal stability of the composite film. Therefore, Ca2+, Fe3+ and Ag+ with an appropriate addition amount can be used as a potential alternative to reinforce collagenous composite materials.