Development and characterization of whey protein isolate and xylan composite films with and without enzymatic crosslinking

Biodegradable food packaging provides an environmentally-conscious alternative to plastic food packaging options. This study investigated whey protein edible films containing 10-40 g xylan/100 g whey protein isolate (WPI). Transglutaminase (TG) was used as a cross-linking agent in WPI-only and 40 g xylan/100 g WPI films. The food packaging properties investigated were water vapor permeability (WVP), oxygen permeability (OP), tensile stress, and % elongation at break. Thermal properties were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Crystallinity and microstructure were assessed using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Composite films containing 40 g xylan/100 g WPI that were also treated with TG showed the greatest improvement in properties important to food packaging. Compared to the WPI-only control films, WVP decreased from 6.41 to 3.89 g mm/m(2) day kPa (p < 0.05), OP decreased from 21.85 to 7.32 cc mu m/m(2) day kPa (p < 0.05), and tensile stress increased from 6.73 MPa to 15.96 MPa (p < 0.05). The % elongation at break decreased significantly from 12.5% in WPI-only films to 5.8-1.4% in all xylan and TG treated films (p < 0.05). The temperature of melting increased from 121 degrees C in control films to a maximum of 166 degrees C in the 20 g xylan/100 g WPI films, indicating increased intermolecular strength. Film microstructure showed separate organization of xylan within films. Crystallinity was identified with increasing xylan content through XRD analysis, suggesting increased polymer packing.

Automated summary

The study found that composite films containing 40 g xylan/100 g WPI treated with TG showed the most significant improvement in properties important for food packaging. Compared to control films, WVP and OP decreased, and tensile stress increased, indicating potential application value of the composite film in food packaging.