【作者】 涂宗财；

【导师】 阮榕生；

【作者基本信息】 南昌大学 ， 食品科学， 2007， 博士

【摘要】 高压处理技术被认为是新的食品加工与保藏技术中最有潜力和发展前途的一种物理改性技术。在动态超高压微射流均质的过程中，物料受到强烈剪切、高速撞击、剧烈震荡、压力瞬间释放等动力作用，可能会导致生物大分子结构的变化，尤其是蛋白质。针对国内外用超高压微射流技术对蛋白质进行改性的研究少、功能性质变化研究深度不够的现状，本论文以大豆分离蛋白、花生蛋白、蛋清蛋白为研究对象，研究动态超高压微射流技术对蛋白进行改性后功能性质的变化规律，初步探讨了蛋白质动态超高压微射流技术改性的机理，并对蛋白经过动态超高压微射流改性后的产物进行了安全性评价。本论文为蛋白改性和动态超高压微射流技术的应用提供了一条新途径，为蛋白质资源的综合利用提供一种新方法。本论文的实验和研究结果如下：1．蛋白经过动态超高压微射流均质后平均颗粒大小有较大的变化：大豆分离蛋白、花生蛋白、蛋清蛋白经过动态超高压微射流均质后平均颗粒尺寸显著减小。大豆分离蛋白在140MPa达到最低为167.2nm，花生蛋白在140MPa达到最低为281.8nm，蛋清蛋白在160MPa达到最低为229.0nm。2．蛋白经过动态超高压微射流均质后功能性基团的变化如下：大豆分离蛋白巯基含量随着压力的升高而升高，在100MPa稍下降后，持续上升至160MPa，花生分离蛋白溶液经过动态超高压微射流处理后，巯基含量随着压力的升高而降低，蛋清蛋白经过动态超高压微射流处理后，巯基含量随着压力的升高而降低，在120MPa又有升高，并且持续上升至160MPa；大豆蛋白、蛋清蛋白疏水基团的含量在100MPa时最高，花生蛋白疏水基团的含量随着处理压力的增大而增大；大豆分离蛋白和蛋清蛋白的紫外吸收都是在80MPa时最高；经过处理后大豆蛋白、蛋清蛋白的DSC曲线波峰均向右偏移。3．不同浓度的蛋白经过动态超高压微射流均质后功能性质变化如下：大豆分离蛋白和花生蛋白的变化相同，低浓度蛋白溶解性的提高更为显著，较高浓度(4％、6％、8％)的蛋白经过动态超高压均质后乳化性均降低了，较高浓度的大豆分离蛋白起泡性会优于较低浓度的起泡性，粘度随着大豆分离蛋白浓度的增大而增大；蛋清蛋白的溶解性随着浓度的增大而增大，2％、4％蛋清蛋白经过动态超高压均质后乳化性会增大，6％、8％的蛋清蛋白溶液的乳化性会降低，6％、8％的起泡性会优于4％的起泡性，不同浓度的蛋清蛋白的流变特性不同。4．不同温度的蛋白经过动态超高压微射流均质后功能性质变化如下：较低温度有利于大豆分离蛋白溶解性的改善，温度对大豆分离蛋白其他功能性质影响不大；温度对花生蛋白的功能性质影响不大；温度会引起蛋清蛋白流变特性发生变化，对其他的功能性质影响不大。5．蛋白经过动态超高压微射流不同均质压力后功能性质变化如下：随着压力的增大，动态超高压微射流处理能使大豆分离蛋白、花生蛋白的溶解性、起泡性、凝胶性、流变性得到改善；随着压力的增大，动态超高压微射流处理对蛋清蛋白的溶解性没有什么影响，而起泡性、凝胶性、流变性得到了改善。6．蛋白经过动态超高压微射流不同均质次数后功能性质变化如下：动态超高压微射流均质次数会使大豆分离蛋白溶解性、乳化性和乳化稳定性降低，起泡性略微改善，但是会获得好的起泡稳定性，同时也会获得更好的流变特性；动态超高压均质次数对花生蛋白的溶解度、乳化性和乳化稳定性、起泡性和起泡稳定性影响不大，会获得更好的流变特性；动态超高压微射流均质次数能使蛋清蛋白溶解度增强，乳化性和乳化稳定性降低，会使起泡性略微改善，而蛋清蛋白的流变特性发生了改变，流变特性发生变化。7．蛋白经过动态超高压微射流均质后二级结构的变化如下：园二色谱的结果表明，大豆分离蛋白中的7S球蛋白受动态超高压微射流的影响比较大，7S球蛋白的α-螺旋比例在经过普通均质后有了提高，β-折叠比例有所下降。动态超高压微射流对11S球蛋白的结构影响不大；红外光谱的结果表明，N-H伸缩振动峰往低波数迁移，说明动态超高压均质对大豆分离蛋白的氢键影响较大，酰胺基吸收峰往高波数迁移，说明β-折叠的减少，不同的均质压力对蛋白的二级结构影响程度不一样。8．动态超高压微射流影响大豆分离蛋白功能性质的机理初探：溶解度的改善可能是由于动态超高压微射流均质使凝聚的球状的大豆分离蛋白逐渐解缔和伸展，蛋白质的水化作用增强；乳化性的影响可能由于动态超高压微射流均质破坏了蛋白质分子内部的疏水相互作用，产生和暴露了更多的疏水性区域，增强了蛋白的表面疏水性，乳化性增强，压力升高到100MPa以上，蛋白质分子的聚集，疏水性的下降，乳化性随之下降；起泡性改善的原因可能是由于动态超高压微射流能使大豆分离蛋白溶解性提高，且使更多的疏水区域暴露了出来；流变性改变的机理可能是由于动态超高压微射流使原来聚集体中存在的弱结合的键断裂了，使蛋白质聚集体解聚，摩擦阻力减小，出现剪切稀化的现象，且流体趋近于牛顿流体；凝胶性的改善可能是由于大豆分离蛋白颗粒的尺寸大大减小，疏水基团的暴露，蛋白质构象的变化，都有利于凝胶网络的形成；成膜性的改善可能是由于动态超高压微射流均质使更多的疏水键打开，蛋白质分子的结合点会增强，相互作用也增强了。9．蛋白经过动态超高压微射流均质后产物的安全性评测如下：经过动态超高压微射流均质处理后的大豆分离蛋白、花生蛋白、蛋清蛋白不影响小鼠的正常生长，没有毒副作用。更多还原

【Abstract】 Dynamic high-pressure processing is considered as one of the most potential and promising physical modification technologies in the latest food processing and preservation development. In the process of dynamic ultra-high pressure micro-fluidization, materials received strong shear, high-speed collision, intensive shake, the instant release of the pressure force and so on, which may lead to the changes in the structures of large molecules, especially in protein. In view of this fact that there are few researches on the application of ultra-high pressure micro-fluidization in the modification of protein, and that the in-depth studies on the functional property changes are still lacking both at home and abroad, this paper focuses on the changes in the functional properties of the soy protein isolate, peanut protein and egg white protein after ultra-high pressure micro-fluidization treatment, preliminary discussing the mechanism of the modification technology of the micro-fluidization in protein and the safety evaluation of the modified products. This paper offers a new approach to the protein modification as well as a new method on the application of dynamic ultra-high pressure micro-fluidization. The experimental results of this paper are summarized showed as follows:1. Mean particle size is greatly changed by dynamic ultra-high pressure micro-fluidization: the mean particle size of the soy protein isolate, peanut protein, and egg white protein significantly decreases after the dynamic ultra-high pressure micro-fluidization treatment. The mean particle size of the soy protein isolate reaches the minimum of 167.2nm at 140MPa; the peanut protein reaches the minimum of 281.8nm at 140MPa; while egg white protein reaches the minimum of 229.0nm at 160MPa.2. Functional groups are changed by dynamic ultra-high pressure micro-fluidization with the results showed as follows: the -SH content of soy protein isolate increases with the pressure, then decreases at 100MPa, and then rises continuously up to 160MPa; after treatment by dynamic ultra-high pressure micro-fluidization, the -SH content in peanut protein decreases with the pressure; while the -SH content in egg white protein decreases with the pressure at first, then increases at 120MPa and continuously rises up to 160Mpa. The content of surface hydrophobicity group of soy protein isolate and egg white protein reaches the maximum at 100MPa; for peanut protein it increases with the pressure; the UV absorbing intensity of soy protein isolate and egg white protein reach the maximum at 80Mpa, and their DSC’s curve peak moves rightward.3. The following is the changes of functional properties of the protein in different concentration after dynamic ultra-high pressure micro-fluidization treatment: the changes of soy protein isolate and peanut protein are similar. The solubility of the lower concentration ones increase significantly, the emulsifying properties of the higher concentration (4%,6%,8%) proteins after micro-fluidization by dynamic ultra-high pressure decrease, the foaming capability of soy protein isolate with higher concentration is better than that with lower concentration and the viscosity of soy protein isolate increases with the concentration; the solubility of egg white protein increases with the concentration, the emulsifying properties of 2% and 4% egg white protein increase, while those of 6% and 8% egg white protein decrease, the foaming capability of 6% and 8% egg white protein are better than that of 4% and the flow pattern of different concentration egg white protein are different.4. The changes in the functional properties of the protein in different temperatures after treatment are listed as follows: lower temperature (20℃) is helpful to the improvement of the solubility of soy protein isolate, but temperature makes little impact on other functional properties; the temperature effect on peanut protein is small; temperature (20℃,30℃,40℃) causes the changes in the flow pattern of the egg white protein, but leaves little changes in other functional properties.5. The effect of pressure on the changes in the functional properties of the protein are indicated as follows: the solubility, foaming capability, gel property and rheological property of soy protein isolate and peanut protein have been improved; the solubility of egg white protein changes little with the pressure but the foaming capability, gel property, and rheological property have been improved.6. The changes in the functional properties of the protein after treatment by different micro-fluidization passes are showed as follows: the solubility, emulsifying property, and emulsifying stability of soy protein isolate decrease, while there is a little improvement in its foaming capability, but it gains a better foaming stability, as the number of pass increases. Meantime, it gains a better rheological property. There are little changes in the solubility, emulsifying property and emulsifying stability, foaming capability and foaming stability of the peanut protein, but it gains a better rheological property. As to egg white protein, the solubility increases, emulsifying property and emulsifying stability decreases, the foaming capability improves a little but its rheological property is changed and its flow pattern is also changed (how).7. The changes in the secondary structure of protein by micro-fluidization are shown as follows: The results of Circular Dichroism (CD) spectroscopy shows that dynamic ultra-high pressure micro-fluidization has a great influence on 7S globulin of soy protein isolate, theα-helix ratio of 7S globulin increases by normal homogenization, whileβ-sheet ratio decreases. There are no significant changes in the structure of 11S globulin. The results of infrared reflectance spectroscopy show that the peak of N-H stretching vibration moves to the low wave number, which confirms that dynamic ultra-high pressure micro-fluidization causes changes in the hydrogen bond of soy protein isolate; and the absorption peak of amide group shows thatβ-sheet decreases, indicating different micro-fluidization pressures make different impacts on the secondary structure of protein.8. The following summarizes the studies on the mechanism of the dynamic ultra-high pressure micro-fluidization treatment on the functional properties of soy protein isolate: the improvement of solubility is made possibly because the dynamic ultra-high pressure micro-fluidization makes globate soy protein isolate disaggregate and extend gradually, and makes the hydration of protein increase. The infuence on emulsifying property may be because homogenization destroys the hydrophobic interaction inside protein, producing and exposing more hydrophobic regions, increasing the contents of the super-hydrophobic characteristics. Thus the emulsifying property increases. However, when the pressure rises above 100MPa, protein molecular aggregates and hydrophobic characteristic decreases, which causes the decrease of emulsifying property. The improvement in foaming capability is partly because the solubility of soy protein isolate increases and discloses more hydrophobic region. The rheological property changes possibly because the weak binding bond is ruptured by dynamic ultra-high pressure micro-fluidization which aggregates originally, and because the protein aggregation is disassociated, friction resistance decreases, shear thinning phenomena appears and the fluid behaves closer to the Newtonian fluid. The improvement of gel property might result from the significant decrease of mean particle size of soy protein isolate, hydrophobic groups expose and protein conformation changes, which help to form the gel network. The improvement of filming ability is partly because homogenization makes more hydrophobic bond unfolded, the bonding sites of the protein molecular increases and interaction increases.9. The preliminary safety evaluation results of the proteins after homogenization by dynamic ultra-high pressure micro- fluidization are showed as follows: soy protein isolate, peanut protein, and egg white protein have little influence on the growth of mouse and no adverse effects were found.更多还原