Effect On The Functional Properties And Enzymatic Hydrolysis Of Wheat Gluten By Pretreatments

The water-insolubility of gluten is one of the major limitations for its extensive use in food processing. To extend its applications, wheat gluten suspension was pretreated to improve its solubility before enzymatic hydrolysis.The effects of several kinds of different pretreatment methods on wheat gluten were explored, including high hydrostatic pressure, ultrasonic wave, addition of NaOH, addition of ethanol, addition of both urea and ethanol, addition of urea, addition of glycerol, addition of both glycerol and urea, addition of Na2SO3, addition of both urea and Na2SO3. The functional properties including solubility, foaming and emulsifying properties were compared to the original gluten. Hydrolytic efficiency of hydrolysis(DH) of gluten were compared, the Fe2+-chelation ability, recovery of protein, changes of molecular and free amino acid of the hydrolysates were determined.Solubility values were figured out as ultrasonic 22.9%, addition of NaOH20.7%, addition of ethanol38.8%, addition of both urea and ethanol 40%, addition of glycerol 28.5%, addition of both glycerol and urea33.8%, addition of Na2SO3 40%, urea pretreatment 43.9%, addition of urea and Na2SO3 51.9%, while original gluten 8%. Wheat gluten suspensions after pretreatments were assessed for their functional properties. Results showed that pretreatments lead remarkably improvement on foaming and emulsifying properties compared to the original gluten.DH values were figured out as ultrasonic wave 16.87%, addition of NaOH15.4%, addition of urea16.92%, high hydrostatic pressure 14.47%, and original gluten 14.89%. In a word, most of the measurements didn't lead remarkable improvement on the efficiency of hydrolysis. Recovery of protein and Fe2+-chelation ability of gluten hydrolysates after all kinds of pretreatment showed obviously promotion. Free amino acid and molecular of the hydrolysates rewarded obvious changes comparing to the original sample. Molecular weight distribution results showed that pretreatments helped to the protein hydrolysis, mean molecular weight were lower and the amount of peptides with molecular weight over 2000Da decreased obviously. The free amino acid results showed that, the amount of free amino acid in the hydrolysates of wheat gluten decreased to less than ten percent of the original sample after pretreatment.The pretreatments lead to a significant decrease of the amount of disulfide bonds and an increase of the amount of–SH. After both urea and Na2SO3 pretreatment, the amount of–SH achieved 47.06μmol/g, and after ultrasound irradiation it achieved 29.4μmol/g, while the original sample was 14.706μmol/g.Structures were determined by CD and FTIR. The results showed that pretreatments lead to significant increase inβ-turns andβ-sheet and obvious decrease inα-helix. To sum up, after pretreatments, the amount ofβ-turns andβ-sheet was increased by over 15%, while the amount ofα-helix decreased by over 10%.