Research Of Preparation And Application Of Degradable Modified Soy Protein Gel

In the thesis, a modified soy protein gel was synthesized by firstlyacylating the soy protein isolate(SPI) with ethylenediaminetetraaceticdianhydride(EDTAD), followed by crosslinking with glutraraldehyde. Theswelling ratio and swelling behavior, metal cheating capacity andbiodegradability were studied.A modified soy protein gel was synthesized by pretreating SPI solution,acylating with EDTAD and followed by crosslinking with glutraraldehyde.The pretreatment of SPI solution was studied, the results showed that theSPI solution had the highest transmittance at 550nm when heating atpH12/65℃for 30 min. The effects of concentration of EDTAD andglutaraldehyde on swelling ratio of soy protein gels were researched, theoptimal swelling ratio was 97.73g/g at m_EDTAD:m_SPI=0.3 and m_SPI:m_Glu=90:2.The acylation reaction was carried out as follows: consuming one lysineresidue averagely incorporated three carboxyls in SPI molecules whenm_EDTAD:m_SPI≤0.3. The IR showed that the number of amido increased afteracylated with EDTAD; The SEM photographs showed that modified soyprotein gels had highly ordered microstructure; the results of tensile testshowed that the breaking strength and elongation at break of gels grew asthe degree of acylation increased.The equilibrium swelling ratio and swelling behavior of modified soyprotein gels were studied. The effects of pH and ionic strength on theswelling ratio of gels were obvious; and the effect of temperature on theswelling ration of gels was neglectable. The swelling and deswellingprocess in pH10.04 and 4.30 buffer solution of modified soy protein gel wasstudied, the result showed that the gel appeared pH-sensitivity. Theswelling behavior of modified soy protein gels was studied and the resultswere as follows: the gels appeared Fickian's diffusion behavior in de-ionized water; appeared non-Fickian' diffusion behavior in normal saline;appeared Fickian's diffusion behavior in alkaline buffer solution; appearednon-Fickian' diffusion behavior in acidic and neutral buffer solution.The modified soy protein gels had a metal chelating capacity to Pb²⁺,Zn²⁺, Cu²⁺and Ca²⁺ ions. The best chelating capacities of the gel were 0.71,0.65, 0.75 and 0.58 mmole per gram of dry gel, respectively. The effects ofmetal concentration,temperature,pH and carboxyl group on the metalchelating capacity of gel were researched.The modified soy protein gels were completely degradable by trysionand pepsin. SDS-PAGE electrophoresis and GPC showed that the molecularweight of enzymatic hydrolyzed products was below 1000. Gels weredissolved and hydrolyzed by fungal on culture mediums or in soil, thehydrolyzed products were absorbed and changed to water and CO₂ bymetabolizing. The results had proved fully biodegradability of modified soyprotein gels.