Properties and Aggregation Characteristics of Rice Residue Proteins Obtained by Different Extraction Methods
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Abstract:
Rice residue proteins were obtained by either alkaline extraction-acid precipitation process (alkali-extraction) or dilute alkali degreasing (purification), and the functional properties (solubility and emulsifying properties) of the resulting two types of proteins were studied. The results showed that between pH 2.0 and 11.0, the solubility and emulsifying properties showed an upward trend after an initial decline, where the alkaline-extracted protein exhibited superior solubility and emulsifying properties compared to the purified protein. To further investigate differences in their functional properties, changes in the aggregation state of the two proteins were studied by measuring surface hydrophobicity, particle size distribution, molecular weight, and surface morphology. The alkaline-extracted sample showed higher surface hydrophobicity and smaller particle size. Scanning electron microscopy showed that the surface of alkaline-extracted protein was rough with packed particles and that of purified protein was relatively smooth with cross-linked particles. The results indicated that the proteins extracted by the above two extraction methods formed different aggregation states. Compared with the purified protein, alkaline-extracted protein showed smaller aggregated particles and exposed more hydrophobic groups, thus exhibiting higher surface hydrophobicity. Therefore, the alkaline-extracted protein exhibited better solubility and emulsifying properties.
