School of Food Engineering, Harbin University of Commerce, Harbin 150028, China.
College of Food Engineering, East University of Heilongjiang, Harbin 150060, China.
Molecules. 2023 Jan 8;28(2):643. doi: 10.3390/molecules28020643.
The effects of Steam Flash-Explosion (SFE) on the physicochemical properties and molecular structure of high-temperature denatured defatted rice bran protein isolate (RBPI) were investigated. The mechanism of SFE treatment on high-temperature denatured defatted RBPI was revealed. The analysis of the physical and chemical properties of RBPI showed that the surface hydrophobicity, characteristic viscosity, and thermal stability of rice bran protein isolate were significantly affected by the pressure of saturated steam and pressure holding time. Under the conditions of 2.1 MPa and 210 s, the surface hydrophobicity index decreased significantly from 137.5 to 17.5, and the characteristic viscosity increased significantly. The peak temperature of denaturation decreases from 114.2 to 106.7 °C, and the enthalpy of denaturation decreases from 356.3 to 231.4 J/g. The higher structure (circular dichroic spectrum and endogenous fluorescence spectrum) of rice bran protein isolate was analyzed by volume rejection chromatography (SEC). The results showed that steam flash treatment could depolymerize and aggregate RBPI, and the relative molecular weight distribution changed greatly. The decrease in small molecules with poor solubility was accompanied by the increase in macromolecules (>550 kDa) soluble aggregates, which were the products of a Maillard reaction. The contents of free sulfhydryl and disulfide bonds in high-temperature rice bran meal protein isolate were significantly increased, which resulted in the increase in soluble aggregates containing disulfide bonds. Circular dichroism (CD) analysis showed that the α-helix content of the isolated protein was significantly decreased, the random curl content was increased, and the secondary structure of the isolated protein changed from order to disorder. The results of endogenous fluorescence spectroscopy showed that the high-temperature rice bran meal protein isolate was more extended, tryptophan was in a more hydrophilic microenvironment, the fluorescence intensity was reduced, and the tertiary structure was changed. In addition, the mean particle size and net surface charge of protein isolate increased in the aqueous solution, which was conducive to the development of the functional properties of the protein.
研究了蒸汽闪蒸（SFE）对高温变性脱脂米糠分离蛋白（RBPI）理化性质和分子结构的影响。揭示了 SFE 处理高温变性脱脂 RBPI 的机制。对 RBPI 理化性质的分析表明，表面疏水性、特性粘度和热稳定性均受到饱和蒸汽压力和保压时间的显著影响。在 2.1 MPa 和 210 s 的条件下，表面疏水性指数从 137.5 显著降低到 17.5，特性粘度显著增加。变性峰温从 114.2 降低到 106.7°C，变性焓从 356.3 降低到 231.4 J/g。采用体积排阻色谱（SEC）分析了 RBPI 的高级结构（圆二色光谱和内源荧光光谱）。结果表明，蒸汽闪蒸处理可使 RBPI 解聚和聚集，相对分子质量分布发生较大变化。溶解度差的小分子减少，同时伴有大分子量（>550 kDa）可溶性聚集物增加，这是美拉德反应的产物。高温米糠蛋白分离物中的游离巯基和二硫键含量显著增加，导致含有二硫键的可溶性聚集物增加。圆二色（CD）分析表明，分离蛋白的α-螺旋含量显著降低，无规卷曲含量增加，分离蛋白的二级结构由有序变为无序。内源荧光光谱分析表明，高温米糠分离蛋白更伸展，色氨酸处于更亲水的微环境中，荧光强度降低，三级结构发生变化。此外，在水溶液中，分离蛋白的平均粒径和净表面电荷增加，有利于蛋白质功能特性的开发。
