Studies On Rheological Properties Of Konjac Glucomannan

Konjac Glucomannan (referred to KGM) is a water-soluble polysaccharide, consisting in tube of konjac. Its excellent biological activity and rheological properties is determined its unique chemical composition and molecular weight characteristics. In this thesis, The structure of KGM have been analyzed, and in addition, rheological property of KGM by concentration, temperature, freezing-thawing, metallic ions, pH, pulse electric fields,γ-irradiation treatment, ultrasonic wave processing and microwave processing were studied, and the mechanism analysis of these factors effected on the rheological property of KGM.(1) Effects of concentration, temperature, freezing-thawing, metallic ions on rheological property of KGM were discussed. KGM have good thickening and thixotropy, the solution of KGM has a high viscosity, and the viscosity decreases with the increasing of shear rate, KGM is pseudoplastic fluid. The viscosity decreases with the increasing of temperature, but 100℃heat treatment had little effect on the viscosity of KGM. The effects of freezing-thawing treatment and metallic ion on the viscosity of KGM are small, but the viscosity decreased after several times of freezing-thawing.(2) Effect of pH value on the rheological property of KGM were studied, and mechanism were discussed through the comparison of rheology of pH-treated samples and those treated samples that dialyzed. The results show that, pH of KGM aqueous solution is 6.56, when viscosity is maximum. Viscosity decreased slightly with acidic pH, but after dialyzed by deionized, the viscosity has some level of recovery. The viscosity can not be restored to its original level with pH<3. The viscosity decreased sharply with alkaline pH. KGM solution rheology changes when pH>10, showed Newtonian fluid behavior, and the viscosity can not be recovered after dialysis. Therefore, KGM solution is irreversible by alkali treatment.(3) Effects of rheological property of KGM treated by 4 kinds of physical fields were studied, and the mechanism were discussed through the comparison of apparent viscosity and intrinsic viscosity of KGM. It is concluded that there are different kinds of effect on the rheological property of KGM by different physical fields. KGM solution treated by high-voltage pulsed electric field, there are little change of the apparent viscosity and intrinsic viscosity, KGM solution maintain the stability of rheological property. The apparent viscosity of KGM solution decreased with the increasing of radiation dose after KGM powder treated by different radiation dose, with the corresponding decreasing of intrinsic viscosity and the tendency of them was similar. The pseudoplastic of KGM solution was gone after high-dose irradiation treatment. There is little effect on the viscosity of KGM solution by short time of ultrasonic wave processing, the viscosity began to drop sharply more than 30 minutes’treatment, but slowly after 90 minutes. The intrinsic viscosity can be reduced accordingly. KGM power treated by 800W 80% microwave in 0.5 minutes, the intrinsic viscosity increased to a small extent, but the increase disappeared when the microwave treatment lasts more time. From the curves of apparent viscosity, the rheological property of KGM is stable by microwave treatment.