长白山核桃球蛋白的提取、分离纯化及其功能性质研究

球蛋白是长白山核桃(Juglans mandshurica Maxim)种仁贮藏蛋白主要组分之一,也是深度开发和利用核桃蛋白资源深加工产品的主要成分。在采用改进的Osborne法提取核桃球蛋白并通过离子交换层析纯化球蛋白的基础上,初步研究其结构特性后,将其功能性质与大豆分离蛋白做对比,进行全面分析,为其在食品加工中的应用提供理论依据。结果表明:制备的球蛋白含量为80.71%,阴离子交换层析图谱出现4个峰,经SDS-PAGE分析其相对分子量集中在14.3 ku和27.0 ku,18.0~21.0 ku,30.0 ku和37.0 ku,30.0 ku、37.0 ku以及44.3~59.0 ku区间;必需氨基酸含量基本符合FAO/WHO成人推荐标准;差示扫描量热(DSC)图谱分析表明JMG干粉出现两个吸热峰,变性温度分别为98.08℃和155.33℃,对应焓值为13.06 J/g、764.80 J/g;傅立叶红外光谱(FT-IR)分析其二级结构,显示JMG以α-螺旋为主;除起泡性和持水性明显低于大豆分离蛋白(SPI)外,JMG其它功能性质均与SPI基本相当。

Extraction and Purification of Globulin from Juglans mandshurica Maxim and Characterization of Its Functional Properties

Globulin is a major protein component of walnuts (Juglans mandshurica Maxim) from the Changbai mountain. The walnut is rich in proteins; therefore, it must be further developed and processed for appropriate utilization of the protein resources. Walnut globulin was extracted by optimized Osborne method, and purified by ion-exchange chromatography. Walnut globulin was subjected to a preliminary structural analysis; subsequently, its functional properties were comprehensively compared (and analyzed) against those of soy protein isolates (SPI), in order to provide a theoretical basis for its application in food processing. The prepared globulin contained 80.71% protein content. Anion-exchange chromatography showed four peaks; the relative molecular weights corresponding to these peaks were concentrated in the ranges 14.3~27.0 kU, 18.0~21.0 kU, 30.0~37.0 kU, and 44.3~59.0 kU, as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The essential amino acid content of the prepared globulin conformed to the Adult Standard Recommendation of the FAO/WTO. The differential scanning calorimetry (DSC) spectrogram of the prepared globulin revealed two endothermic peaks, indicating denaturation temperatures of 98.08°C and 155.33°C, corresponding to enthalpy values of 13.06 J/g and 764.80 J/g, respectively. The Fourier transform-infrared (FT-IR) spectrum revealed that the prepared globulin mainly consisted of alpha helical secondary structures. The functional properties of the prepared globulin, excluding foamability and water absorption (which were significantly lower than those of SPI), were observed to be comparable to those of SPI.