Study On Effects Of Polysaccharides On Characteristics Of Soy Protein Isolate Emulsion Systems And Their Mechanisms

Effects of κ-carrageenan on textural and rheological properties of soy protein isolate(SPI) emulsion gels were studied. Influences of different polysaccharides (sulfate polysaccharide:κ-carrageenan, carboxyl polysaccharide: Carboxymethylcellulose, and neutral polysaccharide: guar gum, methylcellulose) on stabilities of SPI stabilized emulsions were systematically studied. Mechanisms of these polysaccharides affecting emulsion stabilities were discussed in this dissertation. Results were indicated as follows:Studying on effects of κ-carrageenan on SPI emulsion gels indicated that electrostatic interaction remarkably affected gel textural properties of κ -carrageenan, different monovalent cations and anions affected gel textural properties differently, and hydrogen bond was also the main force involving in formation gels. Hydrogen bond, hydrophobic interaction and electrostatic interaction were major forces in the formation of SPI gels.Research results of effects of SPI emulsion droplets on texture properties of κ -carrageenan gels showed that texture properties changed with the changes of oil mass fractions. Phase separation occurred in gels with zero oil mass fractions, and SPI deposited in gel bottoms. Texture properties of κ -carrageenan gels containing SPI emulsion droplets were affected by oil mass fractions and electrostatic interaction between SPI and κ -carrageenan.Textural and rheological properties of SPI emulsion gels changed with pH changing. In pH range investigated, the hardness of gels decreased, while cohesiveness, brittleness, fracture strength, storage moduli and complex moduli increased with pH increasing. Addition of 0.05% κ -carrageenan could remarkably improve textural and rheological properties of SPI emulsion gels, this couid be likely to form coupled gels via electrostatic interaction between SPI and κ -carrageenan. But the cohesiveness and brittleness of gels with 0.2% κ -carrageenan decreased, while the hardness, fracture strength and dynamic viscoelastic mduli remarkably increased, indicating characteristics of phase separation gels.In SPI emulsion systems, electrostatic attraction between κ -carrageenan and SPI occurred at pH 6.5 or 7.0 conditions. When concentrations of κ -carrageenan were very low, carrageenan molecules were adsorbed to protein absorption layer of oil droplets, which increased the repulsion potential energy of oil droplets, and thereby the stabilities of emulsion systems were improved. The net interaction force between κ -carrageenan...