Transglutaminase Cross-linking Whey Proteincalcium Carbonate Composite Film

In this study,whey protein based film was studied in the presence of transglutaminase(TG)and nano-calcium carbonate.The single-factor experiment was conducted to examine the influence of nano-calcium carbonate,glycerol,TGase,and pH on the performance of the composite film,and the transmittance,water vapor permeability,mechanical properties,and solubility was determined to determine the feasibility of the whey protein-based composite film.Results showed that the performance of whey protein-nano-calcium carbonate composite film was superior when whey protein at 10%(w/w),pH 7.5,glycerol was 40% at the mass weight of whey protein,TGase was 6 U/g protein,and the amount of nano-calcium carbonate was 1%.Furthermore,whey protein composite film and its film-forming solution were analyzed by SDS-PAGE,fourier transform infrared spectroscopy(FT-IR)analysis,rheological analysis,scanning electron microscopy(SEM)analysis,contact angle analysis,and thermal stability(DSC)analysis,to characterize and analyze their internal structural changes.SDS-PAGE analysis showed that TGase promotes the crosslinking of whey proteins to form macromolecular polymers.FT-IR infrared spectroscopy showed that there was no obvious change in the absorption peak of the whey protein-nano-calcium carbonate composite film compared with whey protein film,and the characteristic peaks of the whey protein-nano-calcium carbonate composite film after the addition of TGase were smaller or even disappeared at 1547 nm,indicating that TGase changed the conformation of the secondary structure of whey protein.The structural analysis of TGase cross-linked whey protein-nano-calcium carbonate composite film was studied.The rheological study showed that the viscosity of the composite film solution gradually decreased as the addition of nano-calcium carbonate gradually increased,and the viscosity of the composite film solution was gradually increased by TGase.Scanning electron microscopy(SEM)analysis showed that the surface microstructure of the whey protein film after addition of the enzyme was smoother and smoother.After adding the nano-calcium carbonate,the whey protein-nano-calcium carbonate composite film apparentlybecame rough.The contact angle results showed that the contact angle decreased from 53° to42° with the gradual addition of nano-calcium carbonate.TGase made the contact angle of the composite film significantly improved.DSC showed that the denaturation temperature of the composite film increased after TGase treatment,revealing that the modification of the composite film was caused by TGase.The optimum film was applied for practical research and storage experiments and performed on instant noodles seasoning powder,coffee granules,milk candy,fudge and abalone fillets.Whey protein-nano-calcium carbonate was compared with whey protein film,the composite film containing 1% of nano-calcium carbonate has less change in quality than the other two films,and has good package effect.For the instant noodles seasoning powder,coffee,milk candy,abalone sample package.This study provides a theoretical and practical reference for the preparation and performance of whey protein-nano-calcium carbonate composite films,laying the foundation for the application of nanomaterials in edible films.