Mechanical properties of whey protein concentrate based film improved by the coexistence of nanocrystalline cellulose and transglutaminase.

Whey Protein Concentrate (WPC) has been researched as food packaging materials in recent years. However, WPC films own the drawbacks on the barrier ability to water vapor and mechanical properties. In the presented work, Transglutaminase (TGase) and different concentrations of nanocrystalline cellulose (NCC) (0-15% wt. of WPC) were incorporated into the WPC matrix to prepare WPC-NCC composite film, their transmittance, mechanical properties, water vapor permeability and microstructures were investigated and compared with that of WPC films. Results illustrated that NCC as fillers in the protein network blended with WPC markedly improved the mechanical properties. The tensile strength of composite film increased from 1.3 to 3.15 MPa as NCC increased to 15% wt. of WPC. Moreover, TGase took a promoted effect on mechanical properties. The composite film achieved a maximal elongation value of 86.7% when TGase was added at 9 U/g of WPC. SDS-PAGE confirmed that TGase positively facilitated the formation of the protein polymers. FTIR analysis observed conformational changes caused by TGase in the films and implied the interaction between WPC and NCC. Results suggest NCC and TGase have a synergy effect on mechanical properties of WPC based film, and TGase-crosslinked WPC-NCC composite film can be applied as an alternative packaging material.