为探究多糖-蛋白类乳化剂的分子结构(支链度、相对分子质量)对水包油乳液乳化特性的影响,对玉米纤维胶(corn fiber gum,CFG)分别进行酸水解和木聚糖酶水解,得到不同支链度和相对分子质量的CFG,通过美拉德反应与大豆分离蛋白(soy protein isolate,SPI)形成CFG-SPI共价复合物,并制备水包油乳液。利用SDS-PAGE、傅里叶变换红外光谱、粒径和Zeta电位等方法对复合物的结构表征和乳化特性进行研究。结果表明,CFG与SPI通过美拉德反应发生了共价连接,且低支链度/低相对分子质量的CFG更有利于与SPI上的氨基形成共价键;与SPI相比,复合物在等电点(pI 4.5)时的溶解度由11.39%升高至23.25%,说明共价结合可明显提高SPI的溶解性;CFG-SPI共价复合物的乳化性能均优于阿拉伯胶、SPI、CFG及CFG-SPI物理混合物,且CFG支链度是影响乳液特性的关键因素;当CFG相对分子质量相近时,支链度越高,其乳化性能越好,CFG支链度相近时,相对分子质量对乳化特性无明显影响。研究结果将为糖-蛋白类乳化剂的研发和应用提供理论依据。
To explore the effect of molecular structure (branching degree and relative molecular weight) of polysaccharide-protein emulsifiers on the emulsifying properties of oil-in-water emulsions, corn fiber gum (CFG) was hydrolyzed by acid hydrolysis and xylanase hydrolysis to obtain three different branching degrees and three different molecular weights.CFG-SPI conjugates were prepared by Maillard reaction with soy protein isolate (SPI) to prepare oil-in-water emulsions.The structure characterization and emulsifying properties of the conjugates were studied by SDS-PAGE, Fourier transform infrared spectroscopy, particle size, and Zeta potential.Results showed that CFG and SPI were covalently linked by the Maillard reaction, and CFG with a low branching degree/low relative molecular weight was more conducive to forming covalent bonds with amino groups on SPI.Compared with SPI, the solubility of the complex at the isoelectric point (pH 4.5) increased from 11.39% to 23.25%, indicating that covalent binding could significantly improve the solubility of SPI.The emulsifying properties of CFG-SPI conjugates were better than those of gum arabic, SPI, CFG, and CFG-SPI physical mixtures, and the branching degree of CFG was the key factor affecting the emulsion properties.When the molecular weight of CFG was similar, the higher the degree of branching, the better the emulsification performance.When the branching degree of CFG was similar, the relative molecular weight had no significant effect on the emulsifying properties.The research results will provide a theoretical basis for the development and application of sugar-protein emulsifiers.
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