超微粉碎处理对核桃蛋白结构及功能性质的影响

Effects of Superfine Grinding on the Structural and Functional Properties of Walnut Protein

以核桃蛋白为原料,探究超微粉碎对核桃蛋白结构和功能性质的影响。通过对核桃蛋白进行不同频率的超微粉碎处理,得到8种不同粒径的核桃蛋白。采用扫描电子显微镜(scanning electron microscope,SEM)和傅里叶变换红外光谱(Fourier transform infrared spectroscopy,FTIR)研究核桃蛋白结构,并考察超微粉碎对核桃蛋白巯基含量、溶解性、持水性、持油性、起泡性、乳化性等功能性质的影响。研究结果显示,超微粉碎处理后,随着频率降低,核桃蛋白的粒径整体呈减小趋势,核桃蛋白的粒径最小达到10.65μm,比表面积最大为354.2 m2/kg。SEM结果显示经超微粉碎后的核桃蛋白颗粒更细小、更分散,比表面积更大。FTIR研究结果显示,经超微粉碎后的核桃蛋白β-折叠结构比例降低,β-转角结构比例增加。随着超微粉碎频率的减小,游离巯基含量整体呈先增加后降低趋势,35 Hz上超微粉碎处理得到的游离巯基含量最高,为30.01μmol/g;溶解性整体呈先增加后降低趋势;泡沫稳定性、持水性和持油性整体呈下降趋势,与原料相比,15 Hz上超微粉碎处理得到的蛋白持水性下降了59.95%,持油性下降了44.84%;起泡性和乳化稳定性整体呈增加趋势,15 Hz上超微粉碎处理得到的蛋白起泡性为原料的1.92倍,乳化稳定性为原料的1.4倍。因此,超微粉碎处理对核桃蛋白的结构和功能性质有重要影响。

Walnut protein was used as raw material to study the effect of superfine grinding on its structural and functional properties.Eight walnut protein samples with different particle sizes were prepared by superfine grinding under different conditions.Scanning electron microscope(SEM)and Fourier transform infrared spectra(FTIR)were used to study the structure of walnut protein.The effects of superfine grinding on the sulfhydryl group content,solubility,water holding property,oil holding property,foaming properties and emulsifying property of walnut protein were studied,too.The results showed that the particle size of walnut protein was reduced with the decrease of superfine grinding frequency,with minimum particle size of 10.65μm and specific surface area of 354.2 m2/kg.SEM found that the protein was smaller,more dispersed,and had a larger surface area after superfine grinding.FTIR results showed that the ratio ofβ-sheet structure decreased,and the ratio ofβ-turn structure increased after superfine grinding.With the decrease of superfine grinding frequency,the content of free sulfhydryl group first increased and then decreased,the content of free sulfhydryl group of the protein obtained from the upper exit under 35 Hz superfine grinding reached the maximum of 30.01μmol/g.The solubility of walnut protein increased first and then decreased.The foam stability,water-holding and oil-holding property decreased.The water-holding capacity and the oil-holding capacity of the protein obtained from the upper exit under 15 Hz superfine grinding,compared with those of the raw materials,were reduced by 59.95%and 44.84%,respectively.The foaming property and the emulsifying activity increased significantly,the foaming property and emulsifying activity of the protein obtained from the upper exit under 15 Hz superfine grinding were 1.92 times and 1.4 times of the raw material,respectively.Therefore,the structural and functional properties of walnut protein were significantly affected by superfine grinding.