【作者】 孙超；

【导师】 刘晓亚；

【作者基本信息】 江南大学 ， 应用化学， 2005， 硕士

【摘要】 大豆分离蛋白的改性方法主要有物理法、化学法、酶法、生物基因工程法等。本文主要探讨的是大豆分离蛋白与甲基丙烯酸的接枝共聚反应,并对大豆分离蛋白及其接枝产物的溶液性质进行了研究。在8mol/L尿素溶液中,以过硫酸铵为引发剂,β-巯基乙醇为蛋白质变性剂,进行大豆分离蛋白与甲基丙烯酸的接枝共聚反应,用傅立叶红外光谱、13C核磁共振谱图证明甲基丙烯酸已成功接枝到大豆分离蛋白上。研究了引发剂浓度、单体浓度、反应温度及反应时间等对接枝反应的影响,得到了较好的反应条件为:引发剂浓度16 mmol/L,单体浓度2.4 mol/L,反应温度80℃,反应时间4h,巯基乙醇浓度0.05mol/L。提出了较为合理的接枝共聚反应机理。本文对大豆分离蛋白及其接枝产物的溶液性质进行了研究。用流变仪研究了大豆分离蛋白及其接枝产物溶液流变性质。实验结果表明,大豆分离蛋白在尿素体系中表现为牛顿型流体,而其接枝产物在该体系中表现为典型的非牛顿型流体,并且其非牛顿性随溶液浓度的增加而增加。少量的外加盐可以使接枝产物的溶液粘度变小,非牛顿性变弱;而当外加盐增多时,又会增加体系的粘度;降低温度和提高接枝率可以增加溶液的粘度;高于等电点(pH≈4.5)附近随pH值增加,大豆分离蛋白溶液及其接枝产物溶液的粘度都会增加;在较高的pH值(pH﹥10)下,大豆分离蛋白溶液粘度变化不大,而接枝产物溶液粘度却变大。另外,本文还用Zeta电位仪对大豆分离蛋白及其接枝产物溶液的Zeta电位进行了对比研究。发现对大豆分离蛋白的接枝改性可以明显地增加大豆分离蛋白分子表面的静电荷,大豆分离蛋白和其接枝产物浓度的增加可以增加其溶液的Zeta电位;而pH值的增加可以显著减少大豆分离蛋白和其接枝产物溶液的Zeta电位;而外加盐对溶液的Zeta电位影响不大。对大豆分离蛋白进行接技改性,为蛋白质的改性提供了一种新的方法,可以使接枝产物兼具天然高分子和合成高分子的优异性能,这有利于拓宽大豆分离蛋白及其产品的应用范围,使其应用于各种工业领域具有实际的意义。更多还原

【Abstract】 In this paper, the graft copolymerization of Soybean protein isolate （SPI） withmethacrylic acid （MAA） was studied, and the solution behavior of SPI and theirgrafted copolymers （SPI-g-PMAA） were also studied.In this graft copolymerization of SPI with MAA, the ammoniumpersulphate （APS） was used as an initiator, and the 8mol/L urea andβ-mercaptoethanol （ME） were used as protein unfolding agents. The FTIR spectraand ¹³C-NMR spectra of SPI and their grafted copolymers indicated that the MAAhad been grafted on the SPI. The effects of APS, MAA, ME, reaction temperatureand reaction time on graft copolymerization were studied by determining the graftingparameters such as grafting percentage （GP %） and grafting efficiency （GE %）. Theoptimum reaction conditions were obtained as following: [MAA] = 2.4mol/L,[APS] =16mmol/L, [ME] = 0.05mol/L, reaction temperature is 80℃, and reactiontime is 4h. And then the reasonable mechanism of graft copolymerization was putforward by means of the theory deduction.On the basis of the success of graft copolymerization, the solution behavior ofSPI and SPI-g-PMAA were investigated. Firstly, the rheology behaviors of thesolutions of SPI and SPI-g-PMAA were studied by the rheometer. The experimentresults indicated that the urea solutions of SPI were Newtonian fluids, but theSPI-g-PMAA solutions were non-Newtonian fluids and their non-Newtonianproperties increased with the increase of solution concentration. After adding a littlesalt （NaCl）, the viscosity of grafted copolymer solution decreased and thenon-Newtonian properties were weakened, but the viscosity would increase withincreasing of salt concentration. The viscosity of SPI and grafted copolymer solutionincreased when the temperature decreased or the graft percentage （GP %） increased.The viscosity of SPI and grafted copolymer solution had lowest value aroundisoelectric point （pH≈5）;the viscosity of them increased with increasing of pH valuewhen pH﹤8, and then the viscosity of SPI solution varied slightly and that of graftcopolymer solution increased with increasing of pH value when pH﹥10.And then, Zeta potential of SPI and the SPI-g-PMAA solutions were alsostudied by Zeta potentiometer. The static charges on the surface of SPI moleculeswere increased clearly after graft modification. And the values of the Zeta potential ofSPI and SPI-g-PMAA solutions increased with the decrease of the solutionconcentration, or decreased strongly with the increase of pH values. But the additionof salt influenced slightly on the Zeta potential of the solutions.更多还原