超声振荡改性玉米醇溶蛋白及高F值寡肽制备

Modification of Zein by Ultrasound Oscillation and Preparation of Oligopeptides with a High Fischer′s Ratio

摘要:

玉米醇溶蛋白经225 W的超声振荡处理90 min，改善其结构特性，解决50 ℃加热会形成“粘弹性面筋团”的现象。通过扫描电镜、红外光谱、差示扫描量热技术，清晰看到其微观表面形貌由片型韧状转变为块型松散状，变性峰显著减小，酰胺Ι带（1 700~1 600 cm^-1）的吸收强度明显减弱。松散蛋白经Alcalase 2.4L碱性蛋白酶水解及超滤、纳滤膜过滤，得到F值为4.07的粗肽，其中相对分子质量小于1 000的占比97.62%。ɑ-胰凝乳蛋白酶和羧肽酶A依次定向水解粗肽，联合活性炭脱芳，制备F值高达41.87的玉米寡肽，其中苯丙氨酸和酪氨酸仅占总氨基酸的0.73%，相对分子质量180~1 000的占比71.37%。

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.