Shape Memory Properties Of Protein Isolate/Chitosan Edible Films

This thesis mainly studied the intelligence of the edible film based on soy protein isolate and chitosan,which was part of the project "Investigation of Intelligent Structure of Protein-Based Edible Biopolymers".This project was financially supported by Grant from Hi-Tech Research and Development Program of China(number:2008AA10Z308) and International Corporation Project of Jilin Provincial Science & Technology Department Development Program(number:20060717).Soy Protein Isolate is a kind of vegetable protein of high quality and low price, molecules contain many hydrogen bonds,hydrophobic and ionic bond,besides it has many of important features and good film-forming property.Chitin deactivation of chitosan is the product of the base,non-toxic,bio-compatibility and good biodegradable,is good film-forming polymer biology.Chitosan can be applied to medical materials,film materials, sewage treatment,agriculture and many other fields.The molecular structure of chitosan is rich in hydroxyl and amino,easy to carry out chemical modification and give the edible film of shape memory.In this thesis,the author studied the factors which effected shape memory properties of edible film.By homogeneous orthogonality,get the combination which has the best shape memory properties.Using x ray diffraction and scanning electron microscopy to analysis shape memory properties of the film,the repeatability of shape memory properties and the performance of spontaneous under storage conditions.The main contents and conclusions are as follows:1) The four factors of deformation recovery rate are strength,time of strength,time of recovery and temperature of strength.Take the rate of deformation as the main index,by orthogonal test to determine factors which make the film has the best shape memory properties,the appropriate tensile force is 2.5N,the appropriate time is 30s,the appropriate temperature is 70℃,suitable for the deformation recovery time is 60s.The results provide uniform standards to many of the test materials and test conditions for further study microstructure and mechanical properties changes before and after deformation,and ensure the accuracy and stability of the tests.According to orthogonal rotation combination with the second design,set up the regression model according to tensile force,role time,deformation recovery time,role temperature of tensile deformation and the deformation recovery rate, and its test of significance.2) When the edible film is non- stretched,at the peak showing a very wide "Steep peak",which indicates that the edible film is amorphous solid scattering samples.When the edible film after being stretched,it has two prominent peaks on the peak,but not sharp,this means that the sample is not complete in the crystal phase.When the film after deformation, although peak height and peak width are smaller than non-stretched ones,but "Steep peak" has re-emerged,which shows that the internal structure of edible film has great changes before and after deformation.3) Edible film before stretching,the surface covered with large and small,uneven distribution of various shapes of the granular material.Surface is very smooth,small particles have been invisible and the large particles smaller than non-stretched.After deformation,the particles re-emergence,and more quantity of small particles,large particles corresponding decrease on the macro-particles with a certain direction.4) The study evaluated the various factors affecting the shape memory properties,the most important one is the two phases structure.The modified CS is reversible phase and the SPI is stationary phase.5) According to comparing experiments,get the conclusion:before and after films deforming,the tensile strength is increased from not-stretched,recovered to stretched films. The tensile strength of not-stretched film is the smallest.The tensile strength of stretched film is the biggest.The elongation is increased first and then decreased.The elongation of recovered film is the biggest.The elongation of stretched film is the smallest.6) As the increasing of times,tensile strength was increased,elongation was decreased, but slowly.As known in the test,the edible film had stability the mechanical properties of which did not obviously change.The results explained that the shape memory properties of film are repeatable.7) Through the regular measurement,get the conclusion:every 30min the deformation recovery rate of edible films have increased,when placed at 90-120min,both increase of deformation recovery rates gradually slowed down and stabilized.However,at the beginning,the deformation recovery rate at room temperature is much higher than in the refrigerator which indicates that low-temperature has a certain impact on spontaneous recovery of the film.The innovation points of the thesis:1) The influence factors of soy protein isolate and chitosan edible film's shape memory properties have been studied.2) According to x-ray and scanning electron microscopy analyze the microstructure of soy protein isolate and chitosan edible film,the mechanism of shape memory properties has been explained.3) The repeatability of shape memory properties has been proved.Research results in this paper can provide worthwhile test parameters and conclusions for food industry.