Study On Succinylation And Phosphorylation Of Wheat Gluten Protein

Wheat gluten protein(WGP) is a kind of widely used food additive. But its application is limited because of its low solubility. Succinic anhydride and STP were used to modify WGP in this paper.The influence of different factors which include WGP concentration, additive dosage and reaction temperature, pH, reaction time to the extent of modification and functionalities of product were studied. On the basis of one-factor experiments, we selected WGP concentration, additive dosage, reaction temperature and pH as the variables, the extent of modification, solubility, emulsifying activity, emulsifying stability, foaming capacity and foam stability as indexes, using L₉ (3⁴) orthogonal experiment, the following optimum processing conditions for preparation succinyled and phosphoryled WGP were obtained. Succinylation of WGP were: WGP concentration was 10%, succinic anhydride dosage was 15%, reaction temperature was 45℃, pH was 8.5;Phosphorylation of WGP were: WGP concentration was 5%, STP dosage was 15%, reaction temperature was 25℃, pH was 9.0;Multiple modification of WGP were: WGP concentration was 10%, total additive dosage was 25%, succinic anhydride/STP 2:1, succinic anhydride added first. The properties of modified WGP were much improved. SDS-PAGE electrophoresis indicated that succinylation and phosphorylation did improve properties of WGP. FTIR spectra showed that WGP were successfully modified by succinic anhydride and STP, though succinic anhydride and STP were induced to protein molecule to alter its structure and to improve their functionalities.The digestibilities in vitro and lysine validities of succinylated phosphorylated and multiple modified WGP were also studied by chemical methods. The ultimate digesting time of wheat gluten protein was 16h. The digestibilities in vitro and lysine validities of modified wheat gluten protein were declined because of high temperature, pH, Maillard reaction and transformation of amino acid. The decreasing extent of digestibilities in vitro of phosphorylated WGP was less than that of succinylated WGP because of lower reaction temperature.In addition, chemical modificated WGP could also improve the stickiness of dough. Multiple modified WGP improved the stickiness of dough most.