Preparation Of Wheat Gliadin Crude Extracts (EXTs),the Steric Cross-linking Regulation And The Properties Of The Cross-linking Products

This work was based on wheat gliadin crude extracts (EXTs) as substrate of the steric cross-linking reaction catalyzed by microbial transglutaminase (MTGase, EC 2.3.2.13). And the emphasis of this work was the regulation of those steric cross-linking reaction with the addition of exogenous amino donors. The characteristic analysis of the cross-linking products certified the improvement of the emulsion stability of substrate. The main results include three parts:1. Preparation of wheat gliadin crude extracts. The extraction with high content and small particle radius of wheat gliadin was based on the novel combination of solvent extraction method and isoelectric precipitation method with specific ultrasonic treatment. The first part designed three single-factor experiments, involving the volume concentration of ethanol (A), the mole concentration of citrate buffer (B) and the time of ultrasonic treatment (C) respectively, to determine the best threshold for CCD response surface design. The results showed that the best thresholds of A, B, C were 40%?60%,5 mM-15 mM and 20 min-40 min respectively. The best condition for the highest mass ratio of proteins and the smallest radius of micro particles was A= 60%, B= 5mM and C= 29.67 min.2. The regulation of steric cross-linking reaction. The second part selected ethylglycinate (Gly-O-Et),6-epsilon-aminocaproic acid (EACA) and monoethanolamine (MEA) as the amino donors to react with wheat gliadin micro particle suspension (dilution of EXTs in Water according to the volume ratio of 1:4) or its hydrolysates with different degree for different time. The dectection of the residues of amino donors derivatized by Dabsyl-Cl had been estabilished. The emulsion stablility was chosen as the main index to determine the influence of hydrolysis and cross-linking reaction towards micro particle suspension. The results showed that micro particle suspension without hydrolysis displayed the best cross-linking specficity to Gly-O-Et compared with its hydrolysates and the its 2 h cross-linking products performed the best emulsion stability compared with other products, micro particle suspension with 60 min hydrolysis displayed the best cross-linking specificity to EACA compared with the blank without hydrolysis and other hydrolysates, however the 4 h cross-linking products derived from the blank without hydrolysis performed the best emulsion stability compared with other products. Micro praticle suspension with 30 min hydrolysis displayed the best cross-linking specificity to MEA compared with the blank without hydrolysis and other hydrolysates, however the 2 h cross-linking products derived from the blank without hydrolysis performed the best emulsion stability compared with other products.3. Characteristic analysis of steric cross-linking products. According to the preparation of cross-linking products and their emulsion stability index from part two, the best cross-linking products with the addition of different amino donors were chosen as the representatives for further analysis. The results showed that the difference of cross-linking groups among the corresponding products could be identified significantly through Fourier infrared spectrum (FTIR). Thermal stability of EXTs could be varied after cross linking reaction with different amino donors. The radius and zeta-potential of EXTs were relatively stable after cross linking reaction with different amino donors. The cross-linking products of EACA (4 h) displayed the best 3-phase contact angle according to the formula of absorption energy.