以豌豆蛋白(pea protein,PP)和高脂果胶(high methoxyl pectin,HMP)为原料,制备不同pH值的豌豆蛋白-高脂果胶复合物,研究pH对复合物浊度、粒径、电位、乳化活性和稳定性的影响,同时通过荧光光谱、傅里叶红外光谱以及透射电子显微镜对复合物进行了结构表征。结果表明,pH 3.0、6.0和8.0时复合体系分别以不溶性复合物、可溶性复合物和共溶状态存在。与pH 3.0和8.0相比,PP-HMP复合物在pH 6.0时Zeta-电位绝对值、乳化活性和稳定性较高,放置24 d未发生分层现象。傅里叶红外光谱和荧光光谱结果表明,PP和HMP在pH 6.0条件下通过疏水相互作用和氢键相互结合,并且与单独PP相比,PP-HMP复合物的β-转角和α-螺旋相对含量增大,色氨酸残基的暴露程度降低,结构更加有序紧密。透射电镜结果显示,相较于pH 3.0和8.0,PP-HMP复合物在pH 6.0下会呈现尺度分散均匀且形态更加规则有序的结构,适合乳液的制备。研究结果为拓宽PP-HMP复合物在食品中的应用提供参考。
Pea protein and high methoxyl pectin were used as raw materials to prepare the pea protein-high methoxyl pectin (PP-HMP) complex with different pH, and the effects of pH on the turbidity, particle size, potential, emulsifying activity, and stability of the PP-HMP complex were studied. Meanwhile, the structure of the complex was characterized by fluorescence spectroscopy, Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). Results showed that the PP-HMP complex system existed as the insoluble complex, soluble complex, and co-soluble state at pH 3.0, 6.0, and 8.0, respectively. Compared with pH 3.0 and 8.0, the absolute value of zeta-potential, emulsifying activity, and stability of the PP-HMP complex at pH 6.0 were higher, and no stratification occurred after 24 days. FTIR and fluorescence spectra showed that PP and HMP combined through hydrophobic interaction and hydrogen bond at pH 6.0. Compared with PP, the relative content of β-turn and α-helix of the PP-HMP complex at pH 6.0 increased, the exposure of tryptophan residues decreased, and the structure became more orderly and compact. According to TEM results, compared with pH 3.0 and 8.0, the PP-HMP complex exhibited a structure with more uniform size dispersion and more regular morphology at pH 6.0. The PP-HMP complex at pH 6.0 was suitable for the preparation of emulsion. The results provided a reference for expanding the application of the PP-HMP complex in food.
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