Abstract: The recombinant plasmid pUC57-α-gliadin was subjected to homology analysis in this study. The target gene was inserted into the expression vector pET-22b. The recombinant α-gliadin was successfully expressed and purified with 70% ethanol. This α-gliadin was then deamidated with citric acid. The deamidated α-gliadin was characterized by Fourier transform infrared spectroscopy, endogenous fluorescence spectroscopy and scanning electron microscope (SEM). Meanwhile, its effect on the texture of noodles was investigated with a texture analyzer. Results showed that α-helix content decreased while β-sheet content increased; α-helix/β-sheet ratio decreased from 1.00 to 0.64 after the deamidation of α-gliadin indicating that the molecular flexibility of the deamidated α-gliadin increased. The endogenous fluorescence spectrum showed a red shift in λmax, implying that the structure of α-gliadin was extended, leading to exposure of tryptophan residues. The hardness and adhesiveness of noodles were respectively decreased and increased by adding deamidated α-gliadin, which had a lump-like structure with a smooth and uniform surface as observed under SEM.

Key words: α-gliadin, in vitro cloning and expression, deamidation, mechanical properties of noodles