Study On Wheat Gluten-Based Composite Protein Edible Films

With the great development of economy and people's enhanced awareness of green consumption, a large number of chemical packaging materials caused serious ecological problems has received increasing international attention. Plant protein films have excellent oxygen barrier, uniform, transparent, good mechanical properties, easy to digest, nutritious and so on, it becomes the focus of edible films research.Wheat gluten is a by-product of wheat starch production,it include wheat gliadin and wheat glutelin. it can form three-dimensional network structure with water,and has good characteristics of viscoelasticity,extensibility, water absorption, emulsification, film-forming. Wheat gluten film which has a strong toughness, good oxygen barrier and heat sealability, excellent oil resistance, but it has poor resistance and mechanical properties of wet that limits the extensive application of the commercial. Therefore, how to enhance and improve the resistance and mechanical properties of wheat gluten films is the importent and difficult research.This topic used wheat gluten (WG) as base material, using lipids, polysaccharides, corn zein (Zein) to modified, prepared wheat gluten-based edible composite films. The effct of lipids, polysaccharides, zein to mechanical properties, barrier properties,light transmission and anti-bacterial properties were investigated. The best forming conditions of WG-Zein complex protein films were determined.And studied the effect of using of complex protein film liquid on the hazelnut kernel. The main conclusions of the study are as follows:(1) Paraffin, beeswax, and lauric acid were used to modify wheat gluten films,and the effcts were investigated.The results show that add appropriate amount of lipids can effectively increase the water resistance, mechanical and oxygen barrier of wheat gluten film. The WVP and oxygen barrier of composite films have significantly improved with paraffin wax,and decreased 21.32% and 11.25% compared to the control respectively, TS and E increased by 9.13% and 23.24% respectively; But the transmittance of composite films have different decline with addintion of lipids.Infrared spectrum shows,the various components of WG-lipid composite films have good compatibility.Comprehensive consideration, the order of improving of lipids on wheat gluten film properties was paraffin,beewax, lauric acid,and the suitable addition of lipids were 0.1g/gWG-0.25g/gWG.(2) Pectin, chitosan, and carrageenan were used to modify wheat gluten films,and the effcts were investigated.The results show that add the appropriate amount of polysaccharide can significantly increase wheat gluten film transmittance, and when the initial dosage can increase the waterproof membrane, mechanical and oxygen barrier. The highest decrease of WVP and oxygen barrier were 12.75% and 18.54%,TS and E were increased by 20.31% and 30.63%. Comprehensive consideration, the order of improving of polysaccharide on wheat gluten film properties was pectin,chitosan,carrageenan,and the suitable addition of polysaccharide were 0.03g/gWG-0.05g/gWG.The effects of addition of polysaccharide to WG-lipid complex films were investigated. The results show that the effect of polysaccharide to WG-lipid composite films and wheat gluten films have sililar variation,add the pectin to further improve the WG-lipid complex film mechanical properties and oxygen barrier.(3) The best forming comditions of composite protein films were confirmed by single factor and orthogonal test. The results show when the addition level of 25% Zein,55% ethanol, glycerol concentration of 10%, pH 12, heating temperature 70℃, the water vapor transmission rate was 6.01g·m/m2·d·KPa of WG-Zein composite protein film,26.35% lower than control;tensile strength was 3.19MPa, was increased by 32.37%;Blocking oxygen capacity of 21.7 mmol/Kg, were increased by 28.15%; The inhibitory effect of escherichia coli and staphylococcus aureus were 25.5mm and 19.8mm, increased by 36.36% and 32.89% respectively,and its oxygen barrier and antimicrobial properties were better than other WG-based films.(4) Using WG-Zein complex protein film coating liquid on the hazelnut kernel preservation research. The results show that the acid value, peroxide value and acid value of liquid coating preservation hazelnut kernel by the composite protein films were 34.05%, 23.41% and 8.92% lower than the control, the protein of cating group and the control group had no significant loss. It explained WG-Zein protein composite film has good water resistance, resistance properties of oxygen,and can delay the hydrolysis of hazelnut kernel and auto-oxidation, with potential commercial applications.