A Study On Properties Of Composite Films From Wheat Gluten And Cornstarch

In this paper, composite films from wheat gluten and cornstarch were studied and optimized.Firstly, Factors affecting the properties of composite films include pH, preheating temperature, ethanol concentration, drying temperature, amount of cornstarch and glycerol and solid-to-liquid ratio was analyzed. Based on tensile strength (TS), elongation (E), water vapor permeability (WVP) evaluated composite films properties. water vapor permeability and tensile strength as the main index , elongation as the secondary indicators were assessed. The results indicated that: As gluten:starch ratio of 13.5:1.5, and ethanol concentration of 50%, pH 10, addition of glycerol 3ml,, preheating temperature of 70℃, tensile strength was 3.74MPa, water vapor permeability was 2.23 (10^-11 g / m·s·Pa), elongation was 214%.Properties of composite films was better.On this basis, selected the amount of corn starch, the amount of glycerol, pH, preheating temperature effected on water vapor permeability, tensile strength, elongation was studied. By orthogonal regression test, The effect and interaction of each factor are studied. The regression equation of water vapor permeability, tensile strength and elongation have been fitted by the amount of corn starch, the amount of glycerol, pH, preheating temperature.Within the test, the amount of glycerol, pH, preheating temperature has a remarkably effected on tensile strength, elongation, water vapor permeability of composite films . The effect caused by pH is higher on the tensile strength, the effect caused by preheating temperature is higher on water vapor permeability.The amount of corn starch influence on the tensile strength, water vapor permeability significantly. The equation of tensile strength fitted by the amount of corn starch, glycerol, pH, temperature, preheating temperature is:TS=4.34-0.21A-0.30B+0.78C+0.036D+0.065AB-0.47AC-0.11AD-0.42BC-0.21B D-0.22CD-0.57A²+0.031B²+0.007167C²-0.56D²The equation of elongation fitted by the amount of corn starch, glycerol, pH, temperature, preheating temperature is:E=208.40+9.62A+56.58B-20.21C-82.33D+8.25AB+26.33AC-17.25AD+16.76BC-37.75BD+8.50CD-3.39A²-10.35B²-16.77C²-29.23D²The equation of water vapor permeability fitted by the amount of corn starch, glycerol, pH, temperature, preheating temperature is:WVP=2.39+0.24A+0.64B-0.25C+0.75D-0.11AB+0.072AC-0.23AD-0.020BC+0.35BD-0.065CD+0.64A²+0.098B²+0.26C²+0.94D²The optimum ratio is: the amount of corn starch is 1.43%, glycerol is 3.39ml, pH is 10.94, preheating temperature is 68.85℃.Finally, the wheat gluten coating, the composite coating and composite films packaging were used to preserve cherry tomatos. Their formula was in accordance with the optimization of response surface.Compared with good fruit ratio, weight loss rate, soluble solids content, acid content, reducing sugar content, ascorbic acid content, treated and untreated fruit were investigated at 20℃, the results showed that three treatments have a beneficial effect compared to untreatment.The result of the composite coating is better than the wheat gluten coating during the storage. The ascorbic acid content, soluble solids, reducing sugar, organic acid content of the composite coating is higher than the wheat gluten coating, but weight loss of two treatments was not difference significantly at the end of test.The pouch made of gluten and cornstarch composite films was packaged fresh fruits. Compared with the rest of treatment and untreatment, the good fruit ratio and physical and chemical indicators of fruits was improved, and water loss rate was reduced significantly, extending the shelf life of fruits.