Abstract:Zein was treated by ultrasound oscillation at 225 W for 90 minutes to improve its structural characteristics and reduce the formation of viscoelastic gluten dough at 50 ℃. The treated zein was characterized by scanning electron microscopy, differential scanning calorimeter and Fourier transform infrared spectroscopy, respectively. The microscopic surface morphology of zein was clearly observed which changed from lamellar toughness to bulk looseness. Meanwhile, the denaturation peak and absorption intensity of amide I band (1 700~1 600 cm-1) decreased significantly after ultrasound oscillation. Corn crude peptides with a Fisher's ratio of 4.07 were obtained after hydrolyzation by alkaline protease (Alcalase 2.4L), ultrafiltration and nanofiltration. The fraction with molecular weight less than 1 000 accounted for 97.62% in the crude peptides. Furthermore, the directed hydrolysis of corn crude peptides was performed by sequential using of α-chymotrypsin and carboxypeptidase A. Combined with the adsorption of aromatic amino acids by activated carbon, corn oligopeptides with a Fisher's ratio of 41.87 was prepared. The fraction with the molecular weight of 180~1 000 was determined to be 71.37% in the oligopeptides, where the proportion of Phe and Tyr was only accounted for 0.73% within total amino acids.
