Effects Of Konjac Glucomannan On The Properties And Structure Of Wheat Dough

Konjac glucomannan(KGM)has abundant edible value and good health care effect.The dough products made by adding KGM could increase dietary fibrous polysaccharides and strengthen the quality of dough products.In this paper,the interaction among KGM and starch and gluten were explained.The effects of KGM on the properties of wheat dough were studied systematically.The konjac noodles were made and the quality of konjac noodles was analyzed.Firstly,the effect of KGM on the gelatinization and retrogradation characteristics of wheat starch(WS)was investigated.With the concentration of KGM added into starch increased,the viscosity increased,the gelatinization temperature increased,the setback value and the gelatinization enthalpy decreased.The results of water distribution test showed that the relaxation time was decreased,which indicated the fluidity of water was reduced by KGM.During storage,the peak intensity of the diffraction peak,the relative crystallinity and the ratio of peak intensity measured by FT-IR were significantly decreased with the addition of KGM.This suggested that KGM could effectively retard the retrogradation of WS.Secondly,the effect of KGM on gluten protein structure was studied.The effects of KGM addition on the water distribution,thermal properties and structural changes of gluten protein were analyzed.With the increase of KGM,the content of the free sulfhydryl groups decreased gradually and the disulfide bonds increased.And the binding water increased and the water was bound more tightly with the addition of KGM.Secondary structure analysis showed that the ordered structure of KGM-treated gluten protein increased and the random curl structure decreased.The addition of KGM made the structure of gluten protein network appear flaky structure and become more compact.Thirdly,the effects of KGM addition on pasting properties,flour properties,textural properties and color of wheat flour dough were studied.The results showed that the flour quality of dough was improved with the increase of KGM content,and the weakening degree decreased.The gelation of KGM and water increased the viscosity of samples and the gelatinization temperature.The dough with KGM showed reddish yellow color on the whole surface.The texture properties of the dough were improved obviously,the tensile strength increased after adding KGM significantly.Lastly,the best production process of konjac noodle was determined by the single factor experiment and orthogonal experiment.The cooking quality,texture pattern,water distribution and microstructure of konjac noodles and common wheat noodles were determined.The results showed that the optimum technological combination for making konjac noodles was 3%konjac flour dosage,20 min fermentation time and 28?fermentation temperature.The hardness and tensile properties of noodles were improved with the addition of KGM.The breakage rate,dry matter water absorption rate and cooking loss rate of noodles were also increased accordingly.Compared with ordinary noodles,konjac noodles had higher water content and stronger binding to gluten protein and starch.The microstructure also proved this point.In addition,the content of resistant starch in konjac noodles increased,the postprandial blood glucose concentration slowed down.