Fish gelatin-nanoclay composite film. Mechanical and physical properties, effect of enzyme cross-linking, and as a functional film layer

The effect of clay content, homogenization RPM, and pH on the mechanical and barrier properties of fish gelatin/nanoclay composite films was investigated. The addition of clay increased the tensile strength (TS) from 30.31+/-2.37 MPa to 40.71+/-3.30 MPa. The nanoclay composite film had improved oxygen and water barrier properties when compared to neat fish gelatin film. Oxygen permeability decreased from 0.0004028+/-0.0000007 g·m/m 2·day·atm to 0.0001144+/-0.0000162 g·m/m 2·day·atm and the water vapor permeability decreased from 0.0312+/-0.0016 ng·m/m2s·Pa to 0.0081+/-0.0001 ng·m/m2s·Pa. The Small angle x-ray scattering (SAXS) and Transmission electron microscopy (TEM) observations confirmed that the ultrasonification treatment (30 min at 40% output) resulted in exfoliation of the silicates. Intercalation was achieved within the composite film without the ultrasonification treatment.;The fish gelatin solution was cross-linked by the addition of Microbial transglutaminase (MTGase) in an effort to measure the effect on film mechanical and barrier properties. The viscosity of the MTGase treated gelatin solution (2% w/w) increased from 86.25+/-1.77 cp (0 min) to 243+/-12.37 cp (80 min). Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) results indicated that the molecular weight of fish gelatin solutions increased after treatment with MTGase. The increase of molecular weight imparted steric hindrance to intercalation, which also resulted in a marked decrease of intercalation. The tensile strength decreased from 61.30+/-1.90 MPa (0 min) to 57.36+/-4.97 MPa (50 min), and the elongation at break (EB) decreased from 16.73+/-4.47% (0 min) to 13.34+/-5.13% (50 min) at 2% (w/w) MTGase concentration. The oxygen permeability and water vapor permeability were not significantly different as a function of treatment time at 2% (w/w) MTGase concentration. The incorporation of nanoclay to the MTGase treated film decreased oxygen permeability. The SAXS and TEM results suggested that the nanoclay was exfoliated in the MTGase treated fish gelatin film.;A three layer laminant film, utilizing the fish gelatin-nanoclay composite film as the functional barrier, was produced using a pilot scale laminator. The laminant film structure was low density polyethylene (LDPE), fish gelatin-nanoclay composite film, and polyester (PET). The fish gelatin-nanoclay laminant film showed excellent oxygen barrier (0∼50% RH) when compared to a similar laminant structure utilizing an industry standard ethylene vinyl alcohol (EVOH) film as the barrier layer. In addition, the fish gelatin-nanoclay composite film exhibited sufficient bond strength (greater than 500 gf) to both the LDPE and the PET. Therefore, the fish gelatin-nanoclay barrier film has the potential to be used as a functional biopolymer barrier in laminant film structures for various food packaging applications.