白、红、黑三色藜麦分离蛋白的物化性质和功能特性

Physicochemical characteristics and techno-functional attributes of white, red and black quinoa protein isolates

摘要:

藜麦籽含有丰富的蛋白质，可作为食品蛋白来源的重要原料。白色、红色和黑色是藜麦最常见的三种颜色类型，而不同颜色藜麦的蛋白组成及功能特性存在较大差异。以白色藜麦、红色藜麦和黑色藜麦为原料，经正己烷脱脂、NaOH碱溶、HCl酸析出的方法，分别分离提取白色藜麦分离蛋白（WQPI）、红色藜麦分离蛋白（RQPI）及黑色藜麦分离蛋白（BQPI），通过聚丙烯酰胺凝胶电泳、Zeta电位和粒径测定，以及表面疏水性、蛋白溶解性、持水性和持油性测试，还有乳化活性、起泡性和凝胶性测试，考察pH（2.0~10.0）和NaCl浓度（0~0.6 mol/L）对WQPI、RQPI和BQPI三种蛋白的物化性质和功能特性的影响。结果表明，WQPI、RQPI和BQPI三种蛋白主要组分均主要是由酸性亚基及碱性亚基通过二硫键交联的11S球蛋白，还有少量的7S球蛋白，但两者含量存在显著差异。三种蛋白平均粒径及带电性强烈依赖于pH，其表面疏水性随着pH升高而显著降低；远离等电点（约5.0）时的pH均能显著提高蛋白溶解性、乳化性及起泡性，但降低泡沫稳定性。在中性条件下，WQPI、RQPI比BQPI表现出更好的凝胶性和界面性；NaCl对蛋白溶解性、乳化性及起泡性的影响依赖于于其浓度；WQPI、RQPI的凝胶性明显优于BQPI，质量浓度120 g/L的WQPI、RQPI所形成的凝胶，结构完整且有较好的站立性，而只有质量浓度达到180 g/L时，BQPI才基本能够形成具有站立性的凝胶。

Abstract:

Quinoa seeds are rich in proteins, which can be used as an ingredient in food protein sources. White, red, and black quinoa seeds are commonly found, and their protein content and functional properties may differ. In this study, the proteins were isolated and extracted from white, red, and black quinoa varieties, and the physicochemical and functional properties of white quinoa protein isolates (WQPI), red quinoa protein isolates (RQPI), and black quinoa protein isolates (BQPI) were studied under different pH conditions (2.0–10.0) and NaCl concentrations (0–0.6 mol/L). In all three protein isolates, acidic and basic subunits are cross-linked via disulfide bonds, resulting in 11S globulins, along with a small amount of 7S globulins, although their relative contents differ. Protein particle size and surface charge were highly dependent on pH, and their surface hydrophobicity significantly decreased as pH increased. Overall, protein solubility, emulsifying activity, and foaming capacity were significantly enhanced at pH values away from the isoelectric point, while foam stability decreased. The gelling and interfacial properties of WQPI and RQPI were better than those of BQPI under neutral conditions. Concentration-dependent effects of NaCl on protein solubility, emulsification, and foaming were observed. Moreover, WQPI and RQPI gelled markedly better than BQPI.