Effects of three glutenins extracted in acidic, neutral and alkaline urea solutions on the retrogradation of wheat amylose and amylopectin.

Three glutenins (glutenin 1, glutenin 2, and glutenin 2) were extracted in acidic, neutral and alkaline urea solutions respectively. All of the three glutenins are rich in glutamic acid (Glu, >30 %) and proline (Pro, >20 %). Glutenin 1, extracted at pH 5, shows higher contents of hydrophilic amino acids as serine (Ser, 5.25 %), aspartic acid (Asp, 2.99 %), tyrosine (Tyr, 3.11 %), arginine (Arg, 2.09 %) and threonine (Thr, 2.11 %) than the other two glutenins. The retrogradation of three glutenins with amylose/amylopectin indicated that glutenin 1 showed significant inhibition effect on the retrogradation of wheat amylose. The characterizations of amylose retrograded with glutenin 1 by FT-IR, XRD, DSC and solid C NMR showed that new hydrogen bonds between Glu, Tyr and wheat amylose were formed, which prevented the formation of hydrogen bonds between amylose themselves. Glycosidic bonds between some hydroxyl groups of C6 in wheat amylose and certain hydroxyl groups of Ser and Thr in glutenin with specific chain length were present. The macromolecules with steric hindrance prevented the rearrangement of amylose into regular crystals. The retrogradation of wheat amylose was inhibited in this way. This study provides a key targeting step to control the retrogradation of amylose.