Researches On Preparation And Application Of Soy Protein Isolated Composite Film

The edible film of soy protein isolate (SPI) is a kind of green food packaging, which is the important direction of modern packing materials of food research. Carrageenan and glycerol were incorporated into SPI films to improve mechanical properties, water barrier properties and thermal stability, and to improve the practical value of SPI films, and to provide the theoretic basis and technical support for the industrial production of SPI films. The main research contents and results were as follows:The effects of film-forming factors on the properties of composite protein films were investigated through single factor test and orthogonal test, the results showed that the sequence of factors influencing the properties of composite protein films was as follows: carrageenan content> glycerol content> pH value> temperature; the optimal parameters was got:10% carrageenan,40% glycerol on the basis of SPI, pH 9 and temperature 65 ℃.The thermal properties of composite protein films were superior to single films through the TGA and DSC analysis, the thermal stability was improved; To study the internal structure from microscopic aspects, SEM, AFM and FTIR were taken to analyze the interaction between components and the compatible characteristics of the film, the results showed that the molecules of SPI and carrageenan had good compatibility and strengthened the hydrogen bonds to form a stable and dense structure.The effects of environment temperature and relative humidity on film properties were studied, the results showed that with the increase of the temperature, the tensile strength and water barrier properties increased, but the color of films turned yellow; With the increase of the relative humidity, the tensile strength decreased, while the elongation at break increased, the water barrier properties of carrageenan films decreased. According to the membership degree value, films had the best properties in the environment temperature 25℃and relative humidity 53.0%.The preference degree of composite protein films as film tray used in cake food was studied. The Friedman test showed that ordinary cake and film of cupcake had significant difference (a=0.01), film of cupcake and cupcake had significant difference (α=0.01), ordinary cake and cupcake had no significant difference (a=0.01), the sequence of preference degree was that film of cupcake was the first, cupcake was the second, and ordinary cake was the third; The Page test showed that the consumers identified differences between samples, and the given sort consistent with a preset sequence (α=0.01).