Preparation Of Glycosylated Proteins Based On Soy Soluble Polysaccharides And Their Properties

Protein and polysaccharides are two main nutrients in foods and the interaction of them affect the structure of foods.Protein-polysaccharide conjugates formed via Maillard reaction have been widely used to improve the processability in food industry.In this study,soy protein isolate?SPI?and soy soluble polysaccharides?SSPS?were used as raw materials to syntheise SPI-SSPS Conjugate?SSC?,and then fractionated by solubility at pH 4.5?SSC45?and pH 6.5?SSC65?and showed their characterisions,such as structure,intermolecular force and emulsifying properties.The results of the study are as follows:?1?Soy protein isolate-soy soluble polysaccharide conjugates were prepared at 60°C,79%relative humidity for 7 d by Maillard reaction,and then fractionated by solubility at pH 4.5and pH 6.5 and characterized.The covalent attachment of SSPS to SPI was confirmed by sulfate-polyacrylamade gel electrophoresis?SDS-PAGE?and glycation degree analysis;the glycation degree of conjugates was 41.79±0.62%?SSC45?and 36.75±1.76%?SSC65?,respectively.The circular dichroism and intrinsicfluorescence displayed the significant differences on the protein structure between SSC45 and other samples,including?-helix and?-sheet.The turbidity and sulfhydryl content investigation indicated that the solubility of SSC45 was more desirable in acid condition than other components and the sulfhydryls of protein increased after Maillard reaction.?2?The surface hydrophobicity and oil/water interface properties of SSC studied in this paper were to provide the guidance for application of conjugates in terms of emulsification.According to the analysis of external fluorescence and surface hydrophobicity,the hydrophobic groups of protein were covered by polysaccharide which was attached to protein after the Maillard reaction and the SSC45 was the lowest.The PSH of SPI is 5.28,SSM is4.36,SSC45 is 0.43 and SSC65 is 3.36.After heating,more hydrophobic groups of protein of the samples were exposed to the surface,SPI is 13.3,SSM is 17.8,SSC45 is 0.78 and SSC65is 5.47.The interfacial tension analysis showed that the diffusion rate of SSC45 was slowest at the initial stage of adsorption and the interface pressure of SSC45 was the lowest at?₁₀₈₀₀.?3?The soy protein isolate-soy soluble polysaccharide emulsions were fabricated through a laboratory scale homogenizer.Four kinds of the initial emulsions were abotained at pH 7.0;the particle sizes of SPI,SSM,SSC45 and SSC65 were 2?m,6?m,0.23?m and 0.5?m,respectively.At the isoelectric point of SPI,they are 12?m,5.5?m,0.23?m and 1?m,respectively.The emulsion stabilized by SSC45 was pretty stable against pH,ionic strength and thermal treatment compared with SSC65,SSM and native SPI stabilized emulsions.The laser confocal images show that the emulsions prepared by SPI and SSM droplets are flocculated to varying degrees,which is consistent with the particle size results.?4?Orange oil was selected as a flavor ingredient to be loaded directly by SSPS and SSC45.Emulsion?20 wt%orange oil?stabilized by SSPS and SSC45?6 wt%?were spray dried using inlet/outlet air temperature of 175±2/75±2°C,respectively at a pilot scale.The mean droplet size of parent emulsion significantly influenced the stability of the resulting oil powder.Scanning electron microscopy?SEM?and confocal laser scanning?CLSM?images futher displayed the formation of oil powders.The results of headspace solid-phase microextraction showed that the volatile compounds in the oil powder prepared by SSPS were degraded rapidly after storage,while the stability of volatile compounds in the oil powder prepared by SSC45 was high.The successful preparation of oil powder provides a great guiding significance for the research and application of food industry flavor.The reconstituted emulsion of the oil powder prepared by SSC45 showed the smallest particle size after dissolution.The effect of spray drying conditions on the samples should be further studied to improve the performance of the sweet orange oil powder.