大豆分离蛋白-单宁酸-多糖三元复合物的功能特性及结构表征

Functional Properties and Structural Characterization of Soybean Protein Isolate-Tannic Acid-Polysaccharide Ternary Conjugates

摘要:

为了探究单宁酸(tannin acid,TA)、麦芽糊精(maltodextrin,MD)、聚葡萄糖(polydextrose,PD)共价修饰对大豆分离蛋白(soybean protein isolate,SPI)功能特性和结构的影响,采用碱处理法和湿法美拉德反应将TA、MD、PD共价接枝到SPI上,分别得到二元共价复合物(SPI-TA)和2种三元共价复合物(SPI-TA-MD、SPI-TA-PD)。通过十二烷基磺酸钠-聚丙烯酰胺凝胶电泳和反应基团的测定研究SPI-TA、SPI-TA-MD、SPI-TA-PD复合物中共价键的形成以及共价接枝程度。采用紫外吸收光谱和傅里叶变换红外光谱法研究二元、三元共价复合物中SPI结构的变化。通过溶解性、乳化性、起泡性、抗氧化活性、热稳定性和表面疏水性等指标,研究TA、MD、PD的共价接枝对SPI功能性质的影响。结果表明:TA、MD、PD与SPI共价结合改变了SPI的结构,降低SPI二级结构中β-折叠含量；TA接枝当量为(35.56±1.32)μmol/g,MD的接枝度为46.54%,PD的接枝度为32.26%；相比于SPI,SPI-TA-MD、SPI-TA-PD三元共价复合物的溶解性、乳化性、抗氧化活性、起泡性、表面疏水性和热稳定性都显著提高(P<0.05)。研究结果旨在为改善SPI的功能特性和深入了解SPI的改性机制提供理论依据,以期为食品功能因子传递系统,尤其是松籽油乳液传递系统提供新的食品级原料。

Abstract:

To explore the effects of covalent modification of tannin acid (TA), maltodextrin (MD), and polydextrose (PD) on functional characteristics and structure of soybean protein isolate (SPI), TA, MD and PD were sequentially covalently grafted onto SPI by alkali treatment and wet Maillard reaction, and binary conjugate (SPI-TA) and ternary conjugates SPI-TA-MD and SPI-TA-PD were obtained successively. The degree of covalent grafting of SPI-TA with MD and PD was investigated by the determination of reactive groups, and the formation of covalent bond in binary or ternary conjugates was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The structural changes of SPI in binary and ternary conjugates were studied by UV-visible spectra and Fourier transform infrared spectroscopy. The effects of TA, MD and PD on the functional properties of SPI were studied by evaluating solubility, emulsification, foaming performance, antioxidant activity, thermal stability and surface hydrophobicity. The results showed that the covalent binding of TA, MD and PD with SPI changed the structure of SPI and reduced the content of β-sheet in the secondary structure of SPI. The grafting equivalent of TA was (35.56±1.32)μmol/g, the grafting degree of MD and PD was 46.54% and 32.26%, respectively. Ternary conjugates showed significantly higher solubility, emulsification, antioxidant activity, foaming performance, surface hydrophobicity and thermal stability compared with SPI(P<0.05). The results could not only provide a theoretical basis for improving the functional properties and further understanding of the modification mechanism of SPI, but also provide a new food-grade raw material for the design of food functional ingredients delivery system, especially pine seed oil emulsion delivery system.