脉冲电场和pH偏移组合处理对大豆分离蛋白结构及功能特性的影响

郭培锋; 曾佳彦; 钱锐琪; 聂菁; 曾新安; 王瑞

doi:10.13386/j.issn1002-0306.2024050128

脉冲电场和pH偏移组合处理对大豆分离蛋白结构及功能特性的影响

Effect of Combination of Pulsed Electric Field and pH Shifting on Structure and Functional Properties of Soybean Protein Isolates

摘要

摘要: 大豆分离蛋白（soybean protein isolate，SPI）是食品工业中一种重要的植物蛋白。然而，其致密的球形聚集结构导致分子柔韧性降低，严重影响了其功能特性。因此，本文采用脉冲电场（pulsed electric field，PEF）和pH偏移技术对SPI进行改性处理，研究了脉冲电场和pH偏移的三种不同组合处理方式（先PEF后pH偏移、先pH偏移后PEF、PEF联合pH偏移）对SPI结构和功能特性的影响。结果表明：三种方法中，PEF联合pH偏移处理对SPI聚集结构的影响最为明显，处理后的SPI具有最高的溶解度（90.23%）、最小的浊度（0.074）、最大绝对ζ-电位值（44.4 mV）和最小的颗粒大小（63.5 nm）。PEF联合pH偏移处理能够诱导SPI二三级部分的解折叠，使得球状堆积态的SPI转换为“熔球态”，并具有更低含量的α-螺旋和β-折叠，以及更高含量的无规卷曲，蛋白结构整体呈现松散和无序状。经不同方法改性后的SPI均表现出更好的功能特性，对SPI功能特性的改善效果排序如下：PEF联合pH偏移>先pH偏移后PEF>先PEF后pH偏移。与未处理组相比，PEF联合pH偏移得到的SPI的乳化性（EAI）、乳化稳定性（ESI）、起泡活性（FA）和与叶黄素的结合常数分别提高了119.24%、39.33%、59.03%和245.81%。综上，采用脉冲电场和pH偏移的不同组合处理能够显著影响SPI的结构和功能特性，其中PEF联合pH偏移处理能诱导SPI高级结构的更大程度的展开，改善其功能特性。

Abstract: Soybean protein isolate (SPI) is an important vegetable protein source used in the food industry. Its functional properties are negatively impacted by its dense spherical aggregate structure, which reduces its molecular flexibility. In this study, pulsed electric field (PEF) and pH shifting techniques were applied to modify SPI structure. The effects of three different treatment strategies combining pulsed electric field and pH shifting (PEF first followed by pH shifting, pH shifting first followed by PEF, and simultaneous PEF and pH shifting) on the structure and functional properties of SPI were investigated. Among the three methods, simultaneous PEF and pH shifting achieved the most obvious effect on the aggregated structure of SPI. This treated SPI exhibited the highest solubility (90.23%), smallest turbidity (0.074), largest absolute ζ-potential value (44.4 mV), and smallest particle size (63.5 nm). Simultaneous PEF and pH shifting could induce partial unfolding of secondary and tertiary structures in SPI, converting the spherical aggregates into a "molten globule state" that exhibited lower α-helix and β-sheet content and higher random coil content. The overall treated protein structure was loose and disordered. Modified SPI using different methods showed better functional properties. The order of improvement in SPI functional properties was as follows: Simultaneous PEF and pH shifting>pH shifting first followed by PEF>PEF first followed by pH shifting. Compared with untreated SPI, simultaneous PEF and pH shifting treatment of SPI increased the emulsifying activity, emulsifying stability, foaming activity, and lutein binding constant by 119.24%, 39.33%, 59.03%, and 245.81%, respectively. In conclusion, different treatments combining pulsed electric field and pH shifting can significantly affect the structural and functional properties of SPI. Simultaneous PEF and pH shifting treatment can induce the greatest degree of unfolding of the advanced structure of SPI and most strongly improve its functional properties.