蛋白质结构在挤压过程中的变化

Transformations of Protein Structure in Extrusion

研究和明确蛋白质在挤压组织化过程中发生的结构变化,为控制挤压组织化过程中蛋白质的变性提供理论依据。通过分析相关文献,从蛋白质的组分及其分子质量、蛋白质的共价键、蛋白质的二级结构四个方面分析了蛋白质结构在挤压过程中发生的变化。结果认为,挤压后,原料中的主要蛋白质组分含量显著降低,残渣蛋白含量显著增加。挤压后,蛋白质亚基的分子质量分布呈现出向小分子质量转变的趋势。挤压过程中没有异肽键的形成。挤压温度对二硫键含量具有负影响,对自由巯基含量具有正影响。当挤压温度大于160℃时,温度对自由巯基和二硫键含量的影响更明显。水分含量对二硫键含量有正影响,对自由巯基含量有负影响。挤压会导致蛋白质的α-螺旋、β-转角等有序二级结构含量降低。当挤压温度低于180℃时,植物蛋白不会完全转变为无规则卷曲结构。水分含量对蛋白质二级结构的变化没有显著影响。螺杆转速对β-折叠具有负影响,对β-转角具有正影响。

Studying on and clarifying the modifications of protein structure in textural extrusion can provide a theoretical basis for controlling protein denaturation in textural extrusion. Through analyzing the relevant literatures, the transformations of protein structure were analyzed from four terms of protein components, molecular weights, chemical covalent bonds and protein secondary structure during extrusion process. It was concluded that the content of main protein components decreased significantly in raw materials, while that of protein residues increased signifi- cantly after extrusion. The molecular weight distribution of protein subunits showed a trend from higher to lower mo- lecular weight after extrusion. No evidences proved isopeptide bond forming during extrusion process. Extrusion tem- perature had a negative effect on disulfide bond content, but affected free sulfhydryl content positively, especially when the extrusion temperature is higher than 160 ℃, the disulfide bond content and the free sulfhydryl content were more sensitive to the temperature. Moisture content affected the disulfide bond content positively, but affected the free sulfhydryl content negatively. The content of protein ordered secondary structure such as α -helix and β -turn de reased remarkably after extrusion, however, when the temperature was lower than 180 ℃, vegetable protein was not completely changed into random coil structure. Moisture content had no significant effect on the modifications of protein secondary structure. Screw speed exerted a negative effect on the content of β -sheet, but a positive effect on that of β -turn.