Study Of The Manufacture Of Wheat Gluten Treated By Ultra-high Pressure

Wheat gluten,extracted from wheat flour,is a kind of natural vegetable protein,rich in nutrition. But compared with soybean protein and peanut protein,wheat gluten has poor functions on solubility,emulsifying ability and foaming ability,which greatly restrict the scope of its application in food industry.It is of great importance to explore the improvement of wheat gluten's functional properties.Ultra-high pressure food-processing technique has many advantages on sterilization at low temperature,regulating food texture,maintaining food color and flavor,reducing the loss of nutriments.It also has excellent effect on functions of modified food proteins.Wheat gluten was used as processing material in this paper and was modified to enhance its functions with ultra-high pressure technique.The mechanism of processing was discussed and its application on the noodle-processing was also researched.The main conclusions were as follows:1.Ethanol concentration,extraction time,liquid-solid ratio were choosed as factors,the orthogonal experiment showed that the optimal separation condition was as follows:ethanol concentration 70%,extraction time 2 hours,liquid-solid ratio 40∶1.The content of gliadin and glutenin in wheat gluten was 47.3±0.63%and 52.7±0.63%,respectively.Glutamic acid was the amino acid with the most content in the wheat gluten,gliadin and gluten,its content was 40.7%, 55.9%and 46.0%,respectively.Wheat gluten,gliadin and gluten had high content of nonpolarity amino acid and low content of cysteine,the content of nonpolarity amino acid was 33.2%,25.8% and 28.5%,respectively.2.pH value had a notable effect on solubility,emulsifying ability and emulsifying stability, foaming ability and foaming stability within the scope of pH from 3 to 11.The function of wheat gluten was the worst at pH 7.Gliadin had better solubility,emulsifying ability and emulsifying stability,foaming ability and foaming stability than glutenin at the same pH,and its emulsifying ability and emulsifying stability were much better.Gliadin was the main component for the improvement on function of wheat gluten.3.Compared with the contrast,under the condition of pressure from 0.1 MPa to 500 MPa and time from 0 minute to 10 minute,the solubility,emulsifying ability and emulsifying stability, foaming ability and foaming stability of ultra-high pressure treated wheat gluten increased at first and then decreased with increasing pressure and time,but the changing rule of every kind of functions had a little difference.Surface hydrophobicity of ultra-high pressure treated wheat gluten was higher than ordinary wheat gluten and was gradually improved as time extending at the same pressure.Comprehensive analysis of high pressure on functional properties of wheat gluten impact, the optimal condition of ultra-high pressure treated wheat gluten was 400 MPa,10 min.4.The solubility,foaming ability and foaming stability of gliadin and glutenin increased at first and then decreased with increasing pressure at processing time 10 minutes,and the optimal processing pressure of the best functional properties was 400 MPa.The emulsifying ability and emulsifying stability of gliadin increased at first and then decreased with increasing pressure at processing time 10 minutes,and the optimal processing pressure of the best functional properties was 200 MPa.Ultra-high pressure had no significant impact on the emulsifying ability of glutenin. Surface hydrophobicity of gliadin and glutenin increased with improving pressure,and gliadin had higher surface hydrophobicity than glutenin at the same pressure.Ultra-high pressure had no significant impact on solubility of gliadin in 70%ethanol solution,and the solubility slightly decreased only at above 400MPa.The solubility of glutenin in 1%SDS decreased with improving pressure.For example,it decreased from 23.71%at 0.1 MPa to 9.12%at 500 MPa.5.Compared with the contrast,the content of free SH and SS of ultra-high pressure treated wheat gluten decreased and increased with improving pressure,respectively.Ultra-high pressure promoted the formation of SS bonds from free SH bonds partly.The content of free SH and SS of glutenin were greatly influenced by the processing pressure which had a less influence on the content of free SH and SS of gliadin.The spectrum of automatic amino acid analyzer and polyacrylamide gel electrophoresis showed that high pressure did not destroy the primary protein structure of wheat gluten,gliadin and glutenin.Fourier transform infrared spectroscopy,circular dichroism showed that ultra-high pressure promotedα-helical and random coil partly converting toβ-sheet conformation for the secondary structure of wheat gluten and gliadin.Ultra-high pressure had a less effect on the secondary structure of glutenin.Scanning electron micrographs.DSC patterns showed that,compared with the untreated samples,ultra-high pressure promoted wheat gluten protein,glutenin cross-linking polymerization,protein surface structure more closely, uniform,and their peak denaturation temperature increased.Ultra-high pressure had no obviously influence on the surface microstructure of gliadin and its peak denaturation temperature decreased. The mechanism of ultra-high pressure treated wheat gluten was that SH/SS interchange reaction was taken place inter and intra each polypeptide chain of gliadin and glutenin respectively,even among gliadin and glutenin.6.At the addition amount range from 0 to3.5%,ultra-high pressure treated wheat gluten(400 MPa,10 min) and ordinary wheat gluten could improve the wet gluten content of flour,and ultra-high pressure treated wheat gluten improved better than ordinary wheat gluten at the same addition amount.It had greatly influence on the noodle's sensory evaluation score,breaking force, hardness,extending distance and noodle's soup absorbency under the addition of ultra-high pressure treated wheat gluten and ordinary wheat gluten.The quality of noodle processed with ultra-high pressure treated wheat gluten was better than ordinary wheat gluten at the same addition amount.The optimal addition amount of ultra-high pressure treated wheat gluten was 3%,the quality of the noodle and Farinograph property of flour added with 3%ultra-high pressure treated wheat gluten were the best.