Influence Of The Pre-processing On Enzymatic Hydrolysis Characteristics Of Wheat Gluten

With wheat gluten proteins （WGP）as raw materials, neutral protease（E1）, complexprotease （E2） were used to analyze the influence of the STP phosphate processing, citric acidprocessing and superfine comminution of WGP on the composition changes of enzymolysisliquid and the variation law of protein structure. And the enzymatic hydrolysis characteristicswere discussed in details.Orthogonal experiment was used to optimize the STP phosphate processing and theCitric Acid Processing conditions. The former optimum processing conditions were identifiedto be that the additive amount of STP9%was of wheat gluten, the temperature was25°C, pHwas8.5, and processing time was30min. The latter optimum processing conditions wereidentified to be that0.1%（w/v） citric acid, the temperature was25°C, and processing timewas30min.By STP phosphate processing with E1and E2and by citric acid processing with E2inthe course of the hydrolysis, the degree of hydrolysis and protein extraction rate increasedsignificantly compared with the original sample. But by citric acid processing withE1morethan5h the degree of hydrolysis decreased slightly. By superfine comminution processingwith E1and E2, the degree of hydrolysis and protein extraction rate has declined slightly overthe original sample, however, with more than48h, the degree of hydrolysis and proteinextraction rate was not obvious.Capillary zone electrophoresis conditions were identified by experiment: the bare tube（56cm×50μm i.d.）, pH2.0phosphate buffer100mmol·L^-1, under40mbar pressure sampleinjection10s, at25°C,27kV under the separation, detection wavelength214nm; enzymolysisliquid at different time was analyzed and the results showed that enzymolysis liquid had twomain regions of the peptides, at25min and50min; with the enzyme time increases, theabsorption peaks in other regions decreased or disappeared, the two main regions showed agrowth trend; and pre-processing for WGP had a significant influence on early stage.This paper analyses the changes of sulfhydryl/disulfide bond of enzymolysis liquid afterpre-processing: the content of free sulfhydryl was increased to14.24μmol·g^-1and disulfidebond was decreased to42.00μmol·g^-1after WGP was treated by STP processing; the contentof free sulfhydryl was decreased to6.24μmol·g^-1and disulfide bond was increased to47.21μmol·g^-1after WGP was treated by citric acid processing; with the reducing of granularity of WGP, the content of free sulfhydryl was decreased after WGP was treated bysuperfine comminution.Fourier transform infrared spectrometry was applied to analyze the secondary structureof treated WGP by pre-processing, the results showed that: the content of β-sheet and turnwere decreased after WGP was treated by superfine comminution, the ratio of α-helix/β-sheet had a decreasing trend; after WGP was treated by STP processing, β-sheet and β-tumwas decreased to25.9%and30.9%respectively, at the same time the content of α-helix wasalso increased from19.8%to22.9%, and the ratio of α-helix/β-sheet was increased to0.88;after WGP was rtreated by citric acid processing, the content of β-sheet was decreased to31.2%, and the content of α-helix was decreased to17.1%slightly, but the change of thecontent of β-turn and specific value of β-sheet/α-helix was not significant.