Modification Of Vital Wheat Gluten And Its Application In Flour Products By Ultra-High Pressure

Vital wheat gluten has attracted much attention because of its high nutritional value,high yield and low price.However,it contains many hydrophobic amino acids so that its solubility is poor and economic value is low,which limits the application scope of vital wheat gluten.Therefore,an efficient and safe modification method of vital wheat gluten is a research focus at home and abroad.In this study,vital wheat gluten was used as a raw material,and different pressure-holding time?5²5min?,different pressure?100⁵00MPa?and temperature?15³5??were selected to modify by using ultra-high pressure technology.The optimum conditions of modification were determined and the functional properties of vital wheat gluten and modification mechanism by ultra-high pressure treatment were discussed.In addition,effects of pre-and post-modification of vital wheat gluten on dough properties and flour quality were explored.The main results of the experiment were as follows:1.Taking solubility as an index,the test of single factor and Box-Behnken combination was used to optimize the process of ultra-high pressure modification of its solubilization.The optimization results were:the temperature of 19?under pressure 398Mpa treated for 13 min.Under these conditions,the solubility of vital wheat gluten was 0.651 mg/mL.2.Effect of ultra-high pressure modification on functional properties of vital wheat gluten was investigated.Compared with the control group,the hydrophilicity and lipophilicity of vital wheat gluten reached a better equilibrium state by ultra-high pressure treatment.The emulsifying activity and emulsion stability were improved,while reached the maximum at 10min and 400MPa.The decrease of air-water interface surface tension promoted the formation of the interface,so enhanced the foaming capability and foaming stability of vital wheat gluten.However,the change of temperature had a little influence on the foaming property.A large number of hydrophilic and hydrophobic groups were exposed,providing more binding sites for water and oil adsorption and improving their adsorption property.3.Study on the modification mechanism of ultra-high pressure modifiedvital wheat gluten.Compared with the control group,the amino acid composition of the modified vital wheat glutendid not change.It shows that the primary structure of the vital wheat gluten unchanged.Ultra-high pressure treatment destroyed the particle aggregates result in the size decreased,and the D?4,3?reduced the minimum at 10 min and 300 MPa.However,the particle size increased if time was too long and pressure was too large.The particle structure of the control group was compact and the surface was smooth.It breaks up irregular small particles,and the bonding between particles becomes loose.The subunits will be re-bonded and the flake structure and newlysurface will increase.The energy required for initial denaturation temperature and peak denaturation temperaturewill decrease,and the proportion of ordered protein structure will decrease.Meanwhile the proportion of disordered protein structure will increase,and the denaturation enthalpy will decrease Alongwith the increase of the rising ofpressure and pressure-holding time,the free thiol group first increases and then decreases.In addition,the disulfide bond decreased firstly and then increased,but the influence of temperature on it is opposite.The characteristic absorption peak of peptide bond didn't change significantly,while the maximum absorption peak of Trp and Tyr increased firstly and then decreased.The internal residues of Tyr and Trp were exposed in various degree due to the destruction of spatial conformation.The fluorescence spectrogram pattern didn't change butthe maximum fluorescence intensity decreased firstly and then increased.The trend of the change of the surface hydrophobic H₀ was opposite to that of the maximum fluorescence intensity.4.Adding vital wheat gluten of untreated and the optimal modifying condition by ultra-high pressure treatment to wheat flour,The content of wet gluten,water absorption rate,the time of dough formation and dough steadiness,powder index and tensile energy of the mixed flour has a great increase within the addition proportion range from 0 to 5%,and a reduction in weakening grade.At the same addingproportion,the degree of improvement of modified vital wheat gluten was more obvious.The quality of steamed bread and noodle can be effectively improved while adding proportion of modified vital wheat gluten was 3% and 2%respectively.