Study On Compound Modification Of Wheat Gluten

Wheat gluten is a byproduct of the wheat starch industry. The use in food is limited by its water-insoluble characteristic. The aim study of this paper was to modify wheat gluten by MTGase deamitation. In order to prevent simultaneous polymerization of the proteins through the formation ofε-(γ-glutamyl)lysyl crosslinks and use more deamidation reaction of MTGase, we attempted to mask theε-NH2 of lysine in wheat glutens via maillard reaction and citraconylation. This study was to enhance the comprehensive utilization of wheat gluten.First, the wheat gluten reacted with glucose and dextran respectively via Maillard reaction. The effect of different time and protein/carbohydrate ratio on the grafing reation was studied. The result showed that protein/carbohydrate ratio 10:1(w/w), reation time 24 h, the grafing degree of gluten with glucose and dextran were 40% and 20% respectively. The 5% suspension solution of glycosylated glutens was deamidated with microbial transglutaminase 100U/g gluten at 37℃, pH 6.0 for 7 h, the amount of NH3 released in the reaction were 40μM NH3/g protein and 50μM NH3/g protein. Compared with the un-glycosylated glutens, the amount of NH3 released was 31μM NH3/g protein. during the reaction surface hydrophobicity index arised, Nitrogen solubility index reached 20%, water absorption rate reached 5.24g/g sample and 4.43g/g sample respectively, oil absorption rate reached the maximum value that were 4.56g/g sample and 4.29g/g sample respectively after 1 h of reaction. SDS-PAGE showed the high molecule weight subunit of gluten were partially involved in cross-linking during MTGase treatment, new bands appeared in the low molecule weight area.Then, the wheat gluten were treated by citraconylation. The effect of different time and protein/citraconic anhydride ratio on the acylation reation was studied. The result showed that ratio 2/1, reation time 3h, the degree of acylation was 72%. The optimum conditions of decitraconylation were pH 3.0, temperture 35oC, reaction time 3 h. The 5% suspension solution of acylation wheat gluten with MTG 100U/g gluten at 37℃, pH 6.0 for 7 h, the amount of NH3 released during the reaction was 53μM NH3/g protein which is higher than the control gluten of 31μM NH3/g protein, and the solubility property was improved from 23.6% to 27.2%. The surface hydrophobicity index changed unconspicuous, water absorption rate achieved the maximum value 3.68g/g sample after reaction 3 h and oil absorption rate achieved the maximum value 5.37g/g sample after reaction 1 h. The solubility, surface hydrophobicity index and oil absorption rate dropped after decitraconylation, but the water absorption rate raised. SDS-PAGE showed that acylated gluten appeared many new bands during MTGase reaction, and high molecule weight subunit of acylated gluten involved in cross-linking. The diffused and indistinct protein bands appeared after decitraconylation owing to gluten protein with different degrees of deamidaion.The analysis of the second structure showed random coil,α-helix andβ-turn contents of glycated gluten increased during MTGase treatment. Random coil andβ-turn contents of acylated gluten dropped at the intial stage and then arised during MTGase treatment against the contents ofα-helix andβ-turn.