挤压处理对大米蛋白-菊粉挤压共聚物结构和理化性质的影响

Effect of extrusion treatment on the structure and physicochemical properties of rice protein-inulin extruded conjugates

为了改善大米蛋白的功能特性,以大米蛋白和菊粉为原料,通过挤压处理实现二者的糖基化反应,探究挤压温度对大米蛋白-菊粉挤压共聚物结构和理化性质的影响。结果表明:挤压处理制备的大米蛋白-菊粉挤压共聚物具有更高的接枝度,并在挤压温度为135℃时达到最高(34.92%);傅里叶变换红外光谱和荧光光谱证实了大米蛋白与菊粉在挤压作用下发生了共价结合反应,并且挤压处理促使大米蛋白分子链的展开与氨基基团的暴露,从而促进了糖基化反应的发生;此外,挤压处理提高了大米蛋白-菊粉挤压共聚物的溶解性、乳化性、乳化稳定性和起泡性,并降低了其粒径;通过扫描电子显微镜发现大米蛋白-菊粉挤压共聚物具有更加疏松多孔的表面结构。挤压处理结合糖基化反应有效改善了大米蛋白的功能特性,是一种制备大米蛋白-菊粉共聚物的可行方法。

Rice protein is a high quality plant protein resource, but its dense structure will lead to poor solubility of rice protein due to its gluten content of more than 80%, which will limit the application of rice protein. Therefore, it is necessary to modify rice protein appropriately to improve its functional properties, which is of great significance to improve its application value. In order to expand the functional properties of rice protein, in this study, rice protein and inulin were used as raw materials to achieve the glycoylation reaction by extrusion treatment. The screw speed of the extruder was set at 180 r/min, the moisture content was 35%, and the mass ratio of rice protein to inulin was 1∶ 1. The influence of extrusion temperature(75, 90, 105, 120, 135, 150, and 165 ℃) on the structure and physicochemical properties of rice protein-inulin extrusion conjugates was investigated. Furthermore, the differences between natural rice proteins, physical mixtures, rice protein-inulin conjugates prepared by wet heat and rice protein-inulin conjugates prepared by extrusion method were analyzed. The results showed that: the rice protein-inulin extruded conjugates prepared by extrusion method had higher grafting degree and reached the highest degree(34.92%) at the extrusion temperature of 135 ℃;the covalent binding reaction between rice protein and inulin was confirmed by Fourier transform infrared spectroscopy and fluorescence spectroscopy, and the extrusion treatment promoted the unfolding of the protein molecular chain, exposing the amino groups hidden inside, which facilitated the glycosylation reaction to occur. In addition, the extrusion treatment improved the solubility, emulsifying activity, emulsion stability and foaming activity of the rice protein-inulin extruded conjugates as well as reduced the particle size of the rice protein-inulin conjugates. Meanwhile, compared with the natural rice protein, the surface hydrophobicity of rice protein-inulin conjugates prepared by wet heat and rice protein-inulin conjugates prepared by extrusion method decreased by 33.77% and 53.03%, respectively. This was consistent with the results of fluorescence spectroscopy. The surface structure of the rice protein-inulin extruded conjugates was observed to be more loosened and porous using scanning electron microscopy. The above research results indicated that the glycosylation of rice protein and inulin was successfully carried out under the action of extrusion treatment, and the functional properties of rice protein were effectively improved by this process, which is a feasible method to prepare rice protein-inulin conjugates.