【作者】 徐玉兰；

【导师】 杨成；

【作者基本信息】 江南大学 ， 应用化学， 2005， 硕士

【摘要】 本文的工作首先是用丙烯酸接枝改性大豆分离蛋白。选择了8M的脲溶液和疏基乙醇作为变性剂,使大豆分离蛋白分子充分舒展,采用过硫酸铵作为引发剂,对大豆分离蛋白(SPI)进行了接枝丙烯酸(AA)共聚反应。通过傅立转换叶红外光谱(FTIR)、13C固体核磁共振谱(13C-NMR)对接枝产物进行表征,证明接枝成功;以接枝率和接枝效率为考查对象,研究了巯基乙醇用量、引发剂、单体量、反应温度和反应时间对接枝率及接枝效率的影响。得到较佳的反应条件为反应体系体积35mL,大豆分离蛋白用量1g,巯基乙醇用量0.08mol/L ,引发剂量15mmol/L,单体量1.98mol/L,反应温度60℃,反应时间4h。在合成大豆分离蛋白丙烯酸接枝共聚物的基础上,本文利用动态激光光散射(DLS)进一步研究了大豆分离蛋白及其丙烯酸接枝共聚物在水相体系中对pH值的响应性。发现大豆分离蛋白和接枝产物对水相pH值都具有很高的响应性。大豆分离蛋白平均流体动力学半径<Rh>在等电点附近(pH = 4~5)达到最大值。接枝率为27.5%的SPI-g-PAA接枝共聚物的平均流体动力学半径<Rh>在pH为3～4范围内最大,而接枝率为116.7%和134.7%的SPI-g-PAA平均流体动力学半径<Rh>在pH为2～3范围内最大。随接枝率增加SPI-g-PAA在水相体系中的溶解性能越好。本文还研究了碱性内切蛋白酶对大豆分离蛋白及其接枝产物的水解机理。利用动态激光光散射(DLS)、ζ-电位仪对水解过程进行跟踪,结果显示大豆分离蛋白聚集体平均流体力学半径从160nm降到110nm,粒径分布变宽,ζ电位值从-24mv降低到-37mv左右,水解作用在3h内基本结束。利用傅立叶转换红外光谱法(FTIR)对水解前后的大豆分离蛋白进行了表征,结果表明水解后的SPI具有更多的非缔合的自由氨基和羟基。而丙烯酸接枝大豆分离蛋白聚集体在碱性内切蛋白酶作用下平均流体力学半径从161nm降到80nm,粒径分布变宽,ζ电位值从-30mv降低到-40mv左右,水解作用在2h内基本结束。碱性内切蛋白酶对大豆分离蛋白丙烯酸接枝共聚物的降解作用比它对未接枝的大豆分离蛋白的降解作用强。更多还原

【Abstract】 In this study, the graft copolymerization of soybean protein isolate (SPI ) withacrylic acid (AA) using ammonium persulfate (APS) as an initiator was carried out inan aqueous solution. In this copolymerization, the 8M urea and β-mercaptoethanolwere used to be denaturants for SPI. The FT-IR and 13C-NMR spectra of SPI and SPIgrafted acrylic acid copolymer (SPI-g-PAA) indicated that the AA had been grafted onthe SPI. The effects of APS, AA, reaction temperature, reaction time and ME on graftcopolymerization were studied by determining the grafting parameter such as graftingpercentage and grafting efficiency. The experiment results indicated that when theweight of SPI was 1g the optimum condition of reaction were [APS] = 15 mmol/L,[ AA] = 1.98mol/L, reaction temperature = 60℃, reaction time = 4h,[ME]=0.08mol/L. The effect of pH value on the solution behavior of SPI and SPI-g-PAA wasinvestigated by dynamic laser light scattering (DLS). The results indicated that theradius of SPI and SPI-g-PAA aggregates was related to the pH values. The averagehydrodynamic radius of SPI aggregate had the maximum value at its isoelectric point(pH = 4~5). The average hydrodynamic radius of SPI-g-PAA aggregates with the27.5% grafted percentage had the maximum at pH = 3~4. The average hydrodynamicradius of SPI-g-PAA aggregates with the 116.7% and 134.7% grafted percentage hadthe maximum at pH = 2~3. The solubility of the SPI-g-PAA in aqueous solutionincreased with increasing of the grafted percentages. Enzymatic hydrolysis process of soybean protein isolate (SPI) and the PAA-g-SPIcopolymer, the radius distribution of their hydrolysis products were investigated andcharacterized by dynamic laser lights scattering (DLS) and the ζ-potential methods.With the increasing of hydrolysis time, the average hydrodynamic radius ofhydrolyzed SPI aggregates deceased from 160nm to 110nm, the distribution ofhydrodynamic radius of SPI broadened, and the ζ-potential of SPI decreased from-24mv to about -37mv. The FTIR spectra of SPI before and after the hydrolysis byenzymatic (Alcalase3.0T) indicated that the hydrolysates of SPI have much morenon-associated O-H and N-H groups than that of native SPI. The enzymatichydrolysis of SPI finished in 3h. With the increasing of the enzymatic hydrolysis time,the average radius of PAA-g-SPI aggregate decreased from 161nm to 80nm, and theζ-potential of PAA-g-SPI decreased from -30mv to about -40mv. The enzymatichydrolysis of PAA-g-SPI finished in 2h. The hydrolysis ability of enzymatic( Alcalase3.0T) was more stronger for the SPI-g-PAA than for SPI.更多还原