Permeability Of Edible Composite Films Based On Soy Protein Isolate And Chinese Cabbage Fiber

The permeability of edible composite film based on soy protein isolate and Chinese cabbage fiber has been studied, which is part of the project"Basic Research on Intelligent Structures of Edible Protein-based Bio-polymer"(20060717) that subsidized by the Science and Technology Office of Jilin Province, and also part of the Hi-Tech Research and Development Program of China (2008AA10Z308).The development of edible film is one of the research foci of food package industry, and has widely come to attention in some countries. Edible films can be used to substitute the plastic as the internal packaging of food and drug that can be eaten without tearing off. It is convenient, healthy, and free of rejectamenta pollution. The edible films studied in this paper are based on soy protein isolate and Chinese cabbage fiber, in order to resolve current problems of edible films.Edible composite films prepared from soy protein isolate(SPI) and Chinese cabbage fiber(CCF) were investigated. The paper studied on the physical property of the soy protein isolate and Chinese cabbage fiber composite films (SPI-CCF composite films), analyzed the solubility coefficient and diffusion coefficient of water vapor and oxygen in the SPI-fib composite film under different temperature and humidity, and then used the mass transfer theory and polymer theory to establish mathematical model in order to forecast the osmotic property of the SPI-CCF composite films.Besides those, the paper studied the effects of factors such as Chinese cabbage fiber and the dry temperature to the permeability of edible composite films based on soy protein isolate and Chinese cabbage fiber, and used quadratic rotation-orthogonal combination design and regression analysis to establish the regression model of the permeability oxygen and carbon dioxide.The main contents and conclusions are as follows: 1) Adding Cabbage fiber as intensifier agent could increase the tensile strength (TS) but reduce the elongation(E) to break of the SPI-fib composite films. The water vapor permeability(WVP) did not change evidently.2) Adding ethanol as solvent could accelerate the dissolution of soy protein isolate and reduce the forming time of composite film. Adding proper ethanol ratio in composite film would advance the tensile strength and water vapor permeability. With the ethanol infusing, the water vapor permeability of the film first decreased, then reversed when the ratio of ethanol exceeds 10%, for the ethanol added made an impeditive effect on the action process of protein molecule and water molecule,which can promote the cross-link effect of protein molecule.3) Adding stearic acid as emulsifying agent could make an efficient effect to decrease the water vapor permeability of the SPI-fib composite films. As stearic acid ratio in composite films increasing, the tensile strength first enhanced gradually but began to decrease when the ratio of stearic acid exceeded 2%. The water vapor permeability decreased significantly when the amount of stearic acid was added. Because of small density of the lipid, a lipid layer was formed by partial lipid which floats to the surface of composite films by the gravity in the drying process, and the formation of the lipid layer reduced the water vapor's adsorption and swelling in the surface and the diffusion velocity within the films, which can improve the resistance of properties of wetlands of the films.4) Adding sodium dodecyl sulfonate(SDS) to the film-forming solution can change the characteristic of block-wet of the films significantly. When the addition ratio was between 1% and 2%, the WVP of the films was lower 18% than of the films which didn't add SDS. This is because non-polarity part of SDS can adsorb on the non-polarity amino acid residue of the film's structure, which destroys the hydrophobic reciprocity during the border-upon protein molecule and forms well-proportioned reticular structure. When the addition of SDS excessed 3%, the viscosity degree of the film-forming solution added, crosslinking reagent cann't spread around, the institution of the film lacks uniformity, crystal area was formed during linearity molecules, so that the character of the film stiffened and resist pull degree declined.5) With the increasing of the dry temperature, the tensile strength increased When the dry temperature was higher than 70, the ordered arrangement and crosslinking degree of the macromolecule in the film-forming solution was so poor that the tensile strength reduced. The over-high temperature brought on the over-rapid exhalation, which made the film-forming macromolecule be rooted prematurely before they formed imperative collect structure through the ordered crosslink during numerators. This leaded the appearance of crack on the film's surface or the odds of pinhole's thickness.6) The water vapor permeability, the tensile strength and the breaking-elongation of the SPI-fib composite films have been studied by the orthogonal L₁₆(4⁵). In the optimized experiments, cabbage fiber density, sodium dodecyl sulfonate density, ethanol volume density, stearic acid density and dry temperature was chose as five factors, each of them also adopting four levels. The optimum conditions that summarized by variance analysis presented that 1.8% cabbage fiber density, 7.5% ethanol volume density, 2% stearic acid density, 1.5% sodium dodecyl sulfonate density and 70℃dry temperature could decrease the water vapor permeability obviously. The water vapor permeability was 3.21×10^-13g·cm/cm²Â·S·Pa, as well as the film thickness 0.122millimeter, the tensile strength 12.73 MPa and the elongation to break43.56%.7)From the moisture absorption isotherms of SPI-fib composite films, some conclusions are obtained: with the same water activity, the permeability of water vapor of SPI-fib composite film is higher than that of SPI-CCF composite film, but the shape of their moisture absorption are basically the same . The results of Fitting analysis using SPSS software shows that they are fitting perfectly between all test points and cubic curves, similar with the upset sigmoid of most food .8) A regression model on the fiber addition amount of Chinese cabbage, the cloth content, the drying temperature, the film thickness, the tensile strength, the breaking-elongation, the oxygen permeability and the carbon dioxide permeability was established by quadratic rotation-orthogonal combination design, and was carried out by significance test.9) In order to ascertain the sequence of oxygen permeability , carbon dioxide permeability and other factors effecting on the index of composite film, contribution rate method was using to analyze the each test factor influencing on detection index.10) Considering all indicators, the paper has made optimization analysis on the regression model, and ascertained the best craft conditions, that is: cabbage the fiber addition amount 2%, inventory rating70ml, drying temperature 70℃.The innovation points of this paper:1) Edible films based on soy protein isolate and cabbage fiber were studied and the function of four kinds of additions was discussed;2) The property of moisture absorption isotherms of SPI-fib composite films was studied;3) The attempt to study the variation of moisture permeability, oxygen permeability and carbon dioxide permeability after adding cabbage fiber to SPI-fib composite films.