Enhancedment And Characterization Of ?-carrageenan/Konjac Glucomannan Compound Hydrogel

The compound hydrogels of?-carrageenan??-CA?and konjac glucomannan?KGM?is a typical example which take advantage of the interaction of two polysaccharides to improve the defect of a single colloidal.However,the?-CA/KGM compound gel still has the shortcomings of poor mechanical properties,poor stability and easy to break.In order to take advantage of the compound gel,this study explored the method of strengthening its mechanical properties,and analysing its structure and other key characteristics.The enhanced mechanical properties of the compound gel can provide data support for the development of products that require high mechanical strength and high safety?foods,toys for special children or pets,hydrogel masks,diapers,and other products in close human contact?security program.The thesis discussed the practicability of three methods which included the optimization of ion composition,the limited degradation of KGM,the adding of PAAm and saline solution soaking in strengthening the mechanical properties of the compound gels.In addition to mechanical properties,the structure and other important physical properties of?-CA/KGM compound hydrogels were characterized.It was found that K⁺&Ca²⁺compound ions,the limited degradation of KGM,and potassium salt immersion were the effective methods to improve the mechanical properties of?-CA/KGM compound hydrogels.The main research contents and results are as follows:1. Different concentration of KCl,Ca Cl₂and the different ratio of KCl and Ca Cl₂were applied in regulating the mechanical properties of the?-CA/KGM compound gel.This part result showed that the breaking strength and breaking elongation of the compound gel was significantly improved?P<0.05?as the KCl?1.5 g/L?and the Ca Cl₂?0.5 g/L?was used,and a more excellent enhancement result could be obtained when the KCl and the Ca Cl₂were used together at a ratio of 6:4.The same improvement of effect would also show in the hardness and elasticity of the compound gel.The result of rheological measurements showed that the viscoelasticity and the sol-to-gel temperature of the compound gel were improved by those ions,Which indicated that ions promoted the transition of polysaccharides molecular in of the gel changed into the helix from its scattered curl formation.Due to the increased of sol-to-gel temperature,the sol state of gel was shorted and the phase separation was reduced,thus a stronger mechanical property of the gel was obtained.The result of the scanning electron microscope and the low field nuclear magnetic resonance showed that the K⁺and Ca²⁺could promote the formation of the helix structure of the?-CA,which would contribute to penetration of the KGM,and resulted in the strengthen of two kinds of polysaccharides interaction.Therefore,a dense gel network was formed,which resulting a more uniform water distribution in the compound gel with an elevated water holding capacity and a weak water fluidity.2. Five kinds of the A.guripingensis konjac gum,which obtained by hygrothermal degradation which its molecular weight ranges from 137.8 k Da to 621.5 k Da,were applied in the present work to compare the difference of the key performance indicators during the sol-gel transition between them and the?-carrageenan.The results showed that,the sol-to-gel temperature of the compound gel was significantly improved by the partial degraded konjac gum?415.6 k Da?when it was compared with the original one?621.5k Da?,and the transition temperature was increase by 5.98?.Meanwhile,the tensile strength,the breaking elongation and the water holding capacity of the compound gel were significantly improved?P<0.05?as the storage modulus,the shear stress and the apparent viscosity of the compound was moderately elevated by using the partial degraded konjac gum.Besides,a dense and ordered structure of the gel was observed by the SEM.What's more,a greater hardness and elasticity were showed in the compound gel prepared with the partial degraded konjac gum?233.3 k Da?.Although the accurate mechanism relating to the interaction between the konjac gum and the?-carrageenan gum during the gelling at a low temperature still needs to be deepened,an innovative and effective way has been confirmed by us,that is the performance of the konjac/?-carrageenan compound gel can be improved by using the hygrothermal degraded A.guripingensis konjac gum,which provides a direct technical reference for the application of konjac gum.3. In order to improve the mechanical properties of?-CA/KGM compound gel,not only polyacrylamide?PAAm?was added to it,but also a novel strategy that soaking the gel in saline solution was implemented.The tensile property test showed that the saline solution soaking can effectively improve its mechanical properties.When soaked in the KCl solution,the gel has the best tensile properties which the concentration of KCl was200 m M,its tensile strength and breaking elongation increased by 35.59%,31.27%respectively.When soaked in the Ca Cl₂solution,the gel has the best tensile properties which the concentration of Ca Cl₂was 40 m M,its tensile strength and breaking elongation increased by 8.22%,29.13%respectively.The swelling test and low-field nuclear magnetic analysis showed that the dehydration of the hydrogels after saltine solution soaking significantly improved its mechanical properties.Fourier infrared spectroscopy,differential scanning calorimetry,X-ray photoelectron energy spectroscopy,etc showed that after saline solution soaking,the K⁺and Ca²⁺entered the gel which led to the neighboring?-CA and PAAm chains became easier to form a stable network structure.KGM molecules were interspersed in the gel network structure formed by?-CA and PAAm,which caused the H-bonding interaction between the macromolecules were enhanced.The cross-link density increased between the three macromolecules made the network structure of the compound gel orderly,thereby improving its mechanical properties.