Effects of Enzymatic Hydrolysis of Konjac Glucomannan on Tensile Properties of Frozen Dough

To investigate the influence of konjac glucomannan(KGM)and their enzymolysis products(KGM Ⅰ,KGM Ⅱ,KGM Ⅲ)on tensile properties of frozen dough,high performance liquid chromatography,electron scanning microscope,nuclear magnetic resonance and textural analyzer were used. Results showed that,with the extension of freeze-thaw cycle time increasing from 0 to 60 d,the free sulfhydryl contents of frozen dough which without KGM and their enzymolysis products addition increased from 7.81 to 9.65 μmol/L,the molecular weight of gluten protein decreased from 1.98×10⁵ to 1.39×10⁵ Da,β-sheet contents decreased and free water content increased by 3.96%. And gluten network seriously damaged and dough tensile ability decreased obviously. Free sulfhydryl contents of tough with 2.0% KGM Ⅱ addition after 60 d freeze-thaw cycle decreased from 9.65 to 5.38 μmol/L,the molecular weight of gluten protein increased from 1.39×10⁵ to 2.11×10⁵ Da,the proportion of free water decreased,the ability of gluten protein to encapsulate starch granules and dough stretch ability gradually increased. It indicated that 2.0% KGM Ⅱ could significantly inhibit the break of disulfide bond and the change of secondary structure,and prevent the water loss of the dough and maintain the stretching ability of the dough.