该文以普通小米蛋白(common millet protein,MP)为对照,采用十二烷基硫酸钠聚丙烯酰胺凝胶电泳(sodium dodecyl sulfate polyacrylamide gel electrophoresis,SDS-PAGE)、傅里 叶红 外光谱(Fourier infrared spectros-copy,FT-IR)、扫描电镜(scanning electron microscopy,SEM)等方法并测定溶解度(solubility,PS)、持水性(water holding capacity,WA)、乳化性(emulsification capability,EC)等指标对富硒小米蛋白(selenium-rich millet protein,SMP)的理化性质、功能特性及结构进行分析.结果表明,MP与SMP的硒含量分别为0.08、0.63 mg/kg;MP与SMP的必需氨基酸(essential amino acid,EAA)含量分别占总氨基酸含量的51.101%、53.529%;EAA与非必需氨基酸(non-essential amino acids,NEAA)的比值为1.045、1.152;2种小米蛋白分子质量均分布在10~70.2 kDa;随着 pH 升高,小米蛋白的 PS、WA、起泡性(froth capability,FC)、起泡稳定性(froth stability,FS)、EC均呈现先下降后上升趋势,而乳化稳定性(emulsion stability,ES)正好相反;随着温度升高,小米蛋白的PS、WA、持油性(oil-holding property,FA)、FC、FS、EC、ES均呈现先上升后下降趋势(P<0.05);SEM结果显示MP表面有不规则凸起,而SMP表面光滑平整;FT-IR显示2种小米蛋白峰型一致,SMP位置略有后移,同时SMP的α-螺旋、β-折叠、β-转角含量较MP分别高出5.532、2.885、5.506个百分点,无规则卷曲含量则低于MP,说明SMP的结构有序性优于MP.该研究结果为SMP产品的开发利用提供重要理论依据.
In this paper,common millet protein(MP)was used as a control,and the physical and chemical properties,functional properties and structure of selenium-enriched millet protein(SMP)were analyzed by SDS-PAGE,Fourier infrared spectroscopy(FT-IR),scanning electron microscopy(SEM),solubility(PS),water holding capacity(WA),and emulsification capability(EC).Results showed that the selenium contents of MP and SMP were 0.08 mg/kg and 0.63 mg/kg.The essential amino acid(EAA)content of MP and SMP accounted for 51.101%and 53.529%of the total amino acid content.The ratios of EAA to non-essential amino acids(NEAA)in MP and SMP were 1.045 and 1.152,respectively.Molecular weights of both millet proteins were distributed in the range of 10 kDa to 70.2 kDa.With the increase of pH,PS,WA,froth capability(FC),froth stability(FS),and EC of millet protein showed a trend of decreasing first and then increasing,while the emulsion stability(ES)was the opposite.PS,WA,oil-holding property(FA),FC,FS,EC,and ES of millet protein showed a trend of increasing first and then decreasing with the increasing temperature(P<0.05).SEM showed irregular bumps on the surface of MP,while the surface of SMP was smooth and flat.FT-IR showed that the peak patterns of the two millet proteins were the same,with the position of SMP slightly shifted back.Meanwhile,the α-helix,β-folding,and β-turning angle contents of SMP were 5.532,2.885,and 5.506 percentage points higher than those of MP respectively,while the irregular curl content was lower than that of MP,indicating that the structural order of SMP was better than that of MP.The results of the study provide an im-portant theoretical basis for the development and utilization of SMP products.