Sun Lingge, Wu Qingzhi, Mao Xiaoying
School of Food Science and Technology, Shihezi University, Shihezi 832000, China.
Foods. 2022 Aug 12;11(16):2432. doi: 10.3390/foods11162432.
(1) Background: The effects of protein oxidization induced by malondialdehyde (MDA), which was selected as a representative of lipid peroxidation products, on the structure and functional properties of walnut protein were investigated. (2) Methods: Walnut protein isolate was produced by alkali-soluble acid precipitation. The modification of walnut protein isolate was conducted by MDA solutions (0, 0.01, 0.1, 1, and 10 Mm), which were incubated in the dark for 24 h. (3) Results: Increased carbonyl content and the degradation of sulfhydryl groups indicated MDA-induced protein oxidization. The circular dichroism spectra revealed disruption of the ordered protein secondary structure. The change in the tertiary conformation of the MDA-treated protein was observed through intrinsic fluorescence. Small polypeptide chain scission was observed at low MDA concentrations (≤0.1 mM) and protein aggregation was observed at high MDA concentrations (>0.1 mM) using high-performance size exclusion chromatography. Oxidized protein solubility was reduced. Furthermore, the emulsification stability index, foam capacity, and foam stability of walnut proteins were increased after treatment with 0.1 mM of MDA. An excessive concentration of MDA (>0.1 mM) decreased emulsification and foaming properties. (4) Conclusions: These results show that MDA oxidation modified the structure of walnut protein and further affected its function, which should be taken into account in processing walnut protein products.
(1) 背景：以丙二醛（MDA）作为脂质过氧化产物的代表，研究其诱导的蛋白质氧化对核桃蛋白结构和功能特性的影响。(2) 方法：采用碱溶酸沉法制备核桃分离蛋白。用MDA溶液（0、0.01、0.1、1和10 mM）对核桃分离蛋白进行改性处理，并在黑暗中孵育24小时。(3) 结果：羰基含量增加和巯基降解表明MDA诱导了蛋白质氧化。圆二色光谱显示有序蛋白质二级结构受到破坏。通过内源荧光观察到MDA处理后蛋白质三级构象的变化。使用高效尺寸排阻色谱法观察到，在低MDA浓度（≤0.1 mM）下出现小多肽链断裂，在高MDA浓度（>0.1 mM）下出现蛋白质聚集。氧化蛋白的溶解度降低。此外，用0.1 mM的MDA处理后，核桃蛋白的乳化稳定性指数、泡沫容量和泡沫稳定性均有所提高。过高浓度的MDA（>0.1 mM）会降低乳化和发泡性能。(4) 结论：这些结果表明，MDA氧化改变了核桃蛋白的结构，并进一步影响其功能，在加工核桃蛋白产品时应予以考虑。
