盐提和碱提酸沉两种方法提取腰果蛋白的结构及其功能性质分析

使用盐提和碱提酸沉两种提取方法从腰果脱脂粉中提取分离蛋白,并对比研究盐提腰果蛋白(CNSPI)和碱提酸沉腰果蛋白(CNPI)的结构和功能性质。结果表明CNPI和CNSPI在结构、微观形态、功能性质和营养价值等方面有明显差异,CNSPI蛋白含量较高,溶解性和乳化性也优于CNPI,CNPI表现出较好的起泡性。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳结果表明两种提取方法对分离蛋白的亚基组成没有显著影响;本研究使用氨基酸分析仪来测定分离蛋白的营养价值,结果表明两种方法提取的腰果蛋白氨基酸含量无明显差异,其营养价值都远高于腰果脱脂粉。表面疏水性测定结果表明CNPI的表面疏水性显著高于CNSPI。扫描电子显微镜结果表明CNSPI呈现出大量的片状微观结构,而CNPI呈现出少量球状和薄片结合成的不规则形状。圆二色光谱结果显示CNSPI和CNPI中主要二级结构是β-折叠,CNPI中有较多的无规卷曲,约占29.3%,CNSPI有较多的α-螺旋(27.0%)。在中性条件下,CNPI的起泡性为119.00%,CNSPI的乳化性达到30.14 m2/g。

Structure and Functional Characterization of Cashew Nut Protein Prepared by Salt Extraction Method and Alkaline Extraction and Subsequent Isoelectric Precipitation Method

Proteins isolated from defatted cashew nut flour by salt extraction method (CNSPI) and alkaline extraction and subsequent isoelectric precipitation method (CNPI) were evaluated to compare their structural (molecular weight, secondary structure, amino acid composition), micromorphological and functional (solubility, foaming capacity and foam stability, emulsifying activity index and emulsion stability) properties. The results showed CNSPI and CNPI differed significantly in structure, micromorphology, and functional properties. CNSPI exhibited significantly higher protein content, better solubility and emulsifying properties compared with CNPI, while the foaming properties were lower. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the preparation methods had no impact on the primary structure of protein isolates. The nutritive value of protein isolates was evaluated by amino acid composition analysis. Scanning electron microscopy revealed that CNSPI exhibited a massive flaky microstructure while CNPI appeared in an irregular shape as a combination of only a few globules and some flaky plates. Circular dichroism (CD) spectroscopy demonstrated that β-sheet was the major secondary structure in CNSPI and CNPI. CNPI had relatively more random coil (29.3%) and less α-helix (11.9% vs. 27.0%) than CNSPI, which was possibly because alkaline treatment destroyed protein structure and consequently changed functional properties. Under neutral pH condition, the foaming capacity of CNPI was 119.00%, and the emulsion capacity could reach 30.14 m2/g.