不同加工方式对藜麦蛋白质结构与功能特性的影响

Effects of Different Processing Methods on the Structural and Functional Properties of Quinoa Proteins

为探究藜麦加工方式对其蛋白质的影响,采用蒸煮、萌发和挤压膨化处理藜麦并提取蛋白质,对蛋白质结构与功能特性进行分析。结果表明:与对照组(藜麦45℃烘干后粉碎过100目筛)藜麦蛋白相比,pH 7.0时萌发组蛋白溶解度提高了14.12%,而蒸煮和挤压膨化组在不同pH值下溶解度均明显降低;3种处理使蛋白乳化性降低7.09%~21.28%,但乳化稳定性提高至对照组的1.08~2.03倍;萌发组蛋白起泡性(69.58%)和泡沫稳定性(67.86%)最高,而热处理(蒸煮和挤压膨化)组大体上显著降低(P<0.05);差示扫描量热分析结果显示3种处理后蛋白质变性温度略有升高;萌发组蛋白游离巯基含量变化不显著(P>0.05),蒸煮组存在氧化损失,而挤压膨化组游离巯基含量增加至33.20μmol/L;光谱分析显示,处理后藜麦蛋白质发生了变性,萌发组无规卷曲相对含量减少1.96%,而蒸煮和挤压膨化组β-折叠相对含量分别由对照组的58.17%增加至89.42%和100.00%。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳结果表明藜麦蛋白主要分子质量为48~63 kDa及<15 kDa组分,且各组分通过二硫键连接,萌发组亚基增多,而热处理组有聚合物形成。3种加工方式对藜麦蛋白质结构影响不同,因而蛋白质表现出的功能特性也存在差异。

To explore the effect of different processing methods on quinoa proteins,the structural and functional properties of the proteins extracted from cooked,germinated or extruded quinoa were investigated.Results showed that the solubility at pH 7.0 of the proteins from germinated quinoa increase by 14.12%compared to the quinoa proteins from the control group(powder passing through a 100 mesh screen,prepared by drying at 45℃followed by crushing),while a significant reduction in protein solubility was found for the other treatments at all pHs.The three treatments caused a 7.09%–21.28%reduction in the emulsifying capacity of quinoa proteins,but a 1.08–2.03-fold increase the emulsion stability relative to the untreated group.Foaming ability(69.58%)and foam stability(67.86%)of the proteins from germinated quinoa were the highest,while heat treatments(cooking and extrusion)generally significantly reduced foaming ability and foam stability of quinoa proteins(P<0.05).Differential scanning calorimetric(DSC)analysis showed that the denaturation temperature of quinoa proteins was slightly increased by the three treatments.Free sulfhydryl group content was not changed significantly by germination(P>0.05),but reduced by cooking due to oxidation and increased to 33.20μmol/L by extrusion.Spectral analysis revealed that all treatments caused protein denaturation;the proportion of random coil was reduced by 1.96%by germination,while the proportion ofβ-sheet was increased from 58.17%to 89.42%and 100.00%by cooking and extrusion,respectively.Quinoa proteins with molecular masses of 48–63 and<15 kDa were identified by sodium dodecyl sulfonate polyacrylamide gel electrophoresis(SDS-PAGE),and it was deduced that quinoa proteins as well as their aggregates and small subunits may interact by disulfide bonds.Germination increased the number of subunits,while heat treatment led to the formation of aggregates.In conclusion,the three processing methods show different effects on the structure and consequently functional properties of quinoa proteins.