壳寡糖酶法糖基化大豆蛋白提高乳液冻融稳定性及机制研究

Investigation on freeze-thaw stability and mechanism of glycosylated soy protein isolate-chitosan oligosaccharide emulsion by transglutaminase

中文关键词:  大豆分离蛋白  壳寡糖  谷氨酰胺转氨酶  冻融稳定性

英文关键词:soy protein isolate  chitosan oligosaccharide  transglutaminase glycosylation  freeze-thaw stability

中文摘要:

      目的 通过谷氨酰胺转氨(transglutaminase glycosylation, TG)酶催化技术制备壳寡糖(chitosan oligosaccharide, COS)糖基化大豆分离蛋白(soy protein isolate, SPI), 并研究改性产物结构变化及其功能性改进机制。方法 以COS与SPI为原料, 采用TG酶催化技术制备大豆分离蛋白-壳寡糖共价改性产物(SPI-COS)。采用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(sodium dodecyl sulfate-polyacrylamide gel electrophoresis, SDS-PAGE)、傅里叶变换红外光谱(Fourier transform-infrared spectroscopy, FT-IR)、荧光光谱研究SPI-COS的结构特征变化, 采用乳析指数(creaming index, CI)、出油率、絮凝程度(flocculation degree, FD)、聚结程度(coalescence degree, CD)、电子显微镜观察等方法表征不同SPI产物乳液的冻融稳定性。结果 蛋白乳液在经历1、2、3次冻融循环处理后, 与对照SPI相比, SPI-COS乳析指数分别降低了58.66%、25.51%和13.63%, 出油率分别降低了49%、69%和48%, 冻融稳定性显著提高。SDS-PAGE和FT-IR分析表明, SPI与COS形成共价键, SPI-COS二级结构中α-螺旋和β-转角的含量显著减少(P<0.05), 而β-折叠和无规则卷曲的含量显著增加(P<0.05)。微观状态分析表明, 与对照SPI冻融乳液相比, SPI-COS乳液不规则, 聚集体更小, 状态更稳定。结论 酶法糖基化蛋白可以通过改变大豆蛋白理化结构特性, 进而提高其乳液的冻融稳定性, 本研究为制备高冻融稳定性SPI提供理论指导及技术支持, 可以扩大大豆蛋白乳液在冷冻食品中的应用。

英文摘要:

      Objective To prepare soy protein isolate (SPI) and chitosan oligosaccharide (COS) by transglutaminase glycosylation (TG) enzyme catalytic technology, and study the structural changes and functional improvement mechanism of the SPI modified product. Methods In this experiment, the covalent modification of soy protein isolate-chitosan oligosaccharide (SPI-COS) was prepared by TG enzyme catalytic technology using COS and SPI as raw materials. The structural change of the modified SPI-COS was evaluated by the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Fourier transform-infrared spectroscopy (FT-IR), and fluorescence spectra. Changes in the creaming index (CI), oiling off, flocculation degree (FD), coalescence degree (CD), and electron microscopic observation were used to characterize the freeze-thaw stability of different SPI product emulsions. Results Compared with the control SPI, after the protein emulsions were treated with 1, 2, and 3 freeze-thaw cycles, the SPI-COS emulsion creaming index was reduced by 58.66%, 25.51%, and 13.63%; the oiling off was reduced by 49%, 69%, and 48%, and the freeze-thaw stability was significantly improved. SDS-PAGE and FT-IR spectroscopic analysis showed that SPI formed covalent bonds with COS, and the content of α-helix and β-turn in the SPI-COS secondary structure was significantly decreased (P<0.05), while the content of β-folding and random coil was significantly increased (P<0.05). The microstate analysis showed that the SPI-COS emulsion was changed to irregular morphology, and the aggregates were made smaller and more stable than the control SPI freeze-thaw emulsion. Conclusion Enzymatic glycosylation of proteins improves the freeze-thaw stability of soy protein emulsions by modifying their physicochemical structural properties. This study provides theoretical guidance and technical support for the preparation of highly freeze-thaw stable SPI. It expands the application of soy protein emulsions in frozen foods.