Research On Preparation And Application Of Wheat Gluten Composite Film

Wheat gluten is a plant protein derived from agricultural by-products of wheat flour processing. It is a very promising film material as it is rich in resources, relatively low prices, as well as possesses good biodegradability and suitable material properties. In this study, the film-forming process of composite films was optimized by mixing wheat gluten protein with polysaccharides, polyphenols, lipid compounds, such as to improve the oxygen barrier, water resistance and mechanical properties of edible films. This work could improve the practical value of wheat gluten protein and provide theoretical basis and technical support for film production. The main contents and results are given as follows:Effects of film-forming parameters on properties of wheat gluten were investigated by using single factor experiment and response surface design. Using barrier (oxygen permeability) and mechanical (tensile strength) as target, the optimal film-forming conditions as target indicators, the optimum experimental conditions were as follows: pH value 11.4, protein addition amount 10.7 g, and ethanol concentration 57%.Effects of polysaccharides (sodium alginate, guar gum, flaxseed gum, gum arabic),polyphenols (proanthocyanidins, tea polyphenols, apple polyphenols) and lipids(polysorbate 80, stearic acid, lauric acid) on oxygen barrier, mechanical and film-forming properties of protein films were investigated. The optimum additives and their addition amounts were evaluated by membership score, and then the composite contents were optimized by response surface design. The optimal conditions are as follows: the addition amount of flaxseed gum, procyanidins and lauric acid were 0.21 g, 0.15 g and 0.1 g,respectively.The thermal stability of protein film was measured by thermogravimetric analysis.The surface morphologies of protein film were studied by scanning electron microscopy(SEM). The internal microstructure of protein film was analyzed by fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The hydrophobicity of protein film was observed by contact angle test. The antibacterial properties of protein films were also investigated by agar disc diffusion method. The results showed that the thermal stability of the composite film is improved; the cross-section gap is reduced, the film surface is uniform, smooth and compact, indicating good structural integrity; The compatibility between components in composite film is good, thus forming stable and dense network structure; The hydrophobicity of the composite film is higher than that of the blank film; and the composite film can effectively inhibit the growth of bacteria on their surface.Furthermore, we employed wheat gluten composite as edible seasoning packaging materials in the instant noodle products. The preservation experimental results indicated that wheat gluten film was smooth and compact, and could slow down the oxidation rate of the oil, showing good oxygen barrier and oil resistance properties. The water resistance of composite film is also improved, indicating that the composite film has a certain packaing role for instant flour package and vegetable bag in the short term.