Effects of Different Protein Fractions of Foxtail Millet on the Pasting Properties of Starch
Four protein fractions of foxtail millet were gradually removed from the whole flour system according to their solubility,and the changes in the structure and pasting properties of the residues were investigated by scanning electron microscopy(SEM),low-field nuclear magnetic resonance(LF-NMR),Fourier infrared spectroscopy and rapid viscosity analyzer(RVA).The protein fraction-starch blends were also constructed for reverse validation.Overall,prolamin greatly affected the pasting properties of starch,followed by glutelin,while albumin and globulin showed less impact on it.SEM results showed that prolamin did not connect or encapsulate the starch granules,suggesting that it did not constitute a physical barrier to the pasting of starch;while,glutelin tightly surrounded and connected the starch granules.Combining the results of RVA and LF-NMR,as well as the characteristics of protein fractions,it was believed that prolamin in-duced a hydrophobic effect which further increased the mobility of water molecules,thus promoting the water absorption,swelling and pasting properties of starch.However,glutelin decreased the peak viscosity and breakdown value,and in-creased the pasting time of starch,indicating that it had a limiting effect on starch pasting.
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