Preparation of Glycosylated Walnut Protein Isolate-Inulin Conjugate and Analysis of Its Properties

Abstract

To improve the solubility of the walnut protein, it was modified through glycosylation. The preparation process of the walnut protein isolate-inulin conjugate was optimized by single-factor and response surface tests. To determine the structural and functional properties of walnut isolated proteins-inulin conjugate, infrared spectra, endogenous fluorescence spectra, solubility and emulsification properties were studied. Results showed that when the reaction temperature was 89 ℃, the reaction time was 75 min, the mass ratio of protein to sugar was 1:2, and the walnut protein isolate-inulin conjugate could reach a maximum solubility of 83%, which was 47% higher than that of walnut isolated protein. Fourier infrared spectroscopy and fluorescence spectroscopy analyses showed that the walnut isolated protein and inulin were joined by covalent bonding, that their shape changed from scattered small granular particles into a sheet structure, and that their fluorescence intensity remarkably reduced. Compared with walnut isolate protein, the foamability and foam stability of walnut protein isolate-inulin conjugate increased by 49% and 23%, respectively, and the emulsification index increased by 17%. These results indicate that protein modification through glycosylation improved the structure and properties of the products. This paper would provide a new method for the processing and utilisation of walnut isolate protein and broadening the field of walnut protein processing and utilization.

Keywords

• walnut protein isolate
• inulin
• glycosylation modification
• structural properties
• functional properties