Konjac Glucomannan Gel Research Articles

KGM and PMAA based pH-sensitive interpenetrating polymer network hydrogel for controlled drug release

Sequential interpenetrating polymer networks (IPN) hydrogels based on konjac glucomannan (KGM) and poly(methacrylic acid) (PMAA) were prepared by immersion of a solution of methacrylic acid (MAA) monomer with cross-linker N,N′-methylenebisacrylamide (MBAAm) and initiating into a pre-fabricated dried KGM gel. Polymerization and cross-linking of MAA inside the KGM network resulted in a novel biodegradable pH-sensitive IPN hydrogel. The studies on the swelling behavior of IPN hydrogels reveal their sensitive response to environment pH value. It was possible to modulate the degree of swelling of the IPN gels by changing the KGM/PMAA ratio and the cross-linking density of the PMAA component. The KGM component in the IPN can be degraded by β-glycosidase Mannaway25L. In vitro drug release behavior of IPN hydrogels were investigated under different environments using model drugs 5-fluorouracil. The results suggested that such an IPN hydrogel can be exploited as carrier candidate for colon-specific drug delivery.

Removal properties of dissolved boron by glucomannan gel

Boron ions have long been known to form complexes with the cis-diol group of a polysaccharide. Konjac glucomannan (KGM) which is one of polysaccharides was used to remove dissolved boron in this study. KGM forms a complex with boron, but does not remove boron from contaminated waters as well as other polysaccharides because of its high water solubility. Therefore, the removal efficiencies of dissolved boron were examined using both an insoluble KGM gel and KGM semi-gel. The former did not remove dissolved boron, but the latter did. The difference in the ability of boron removal was due to the presence of diol group inside. KGM loses free diol group during the process of gelation. On the other hand, the semi-gel gelated only surface layer in water has diol group inside. The boron removal capacity of the semi-gel was highest at pHs⩾11, when the boron species is present as B(OH)4-. The capacity was slightly increased by the addition of Al, Ca and Mg under high pH conditions. This was due to co-precipitation of boron with Ca dissolved from the semi-gel. The boron adsorbed to the semi-gel easily was desorbed under low pH conditions and the hysteresis was not found.

Effect of degree of deacetylation on physicochemical and gelation properties of konjac glucomannan

Gelation behaviors of konjac glucomannan (KGM) samples with different degree of deacetylation (DD) obtained using a heterogeneous deacetylation method were studied by dynamic viscoelastic measurements in order to probe the role of acetyl groups in the gelation process of KGM and types of molecular forces responsible for gel formation. Molecular parameters and structure of KGM samples were determined by GPC–MALLS and FT-IR spectroscopy. It was found that water solubility of KGM decreased with increasing DD, providing evidence further that the presence of acetyl groups confers water solubility on KGM. Rheological measurements suggested that hydrogen bonding and hydrophobic interaction are both presented in KGM gels, hydrophobic interaction was strengthened whilst hydrogen bonding was weakened with increasing DD. A faster gelation rate and a more elastic modulus were facilitated by raising temperature or increasing KGM sample concentration. The conditions under which gelation can occur became easier with increasing DD.

Adsorption Behaviors of Benzonic Acid by Carboxyl Methyl Konjac Glucomannan Gel Micropheres Cross-Linked with Fe3+

Ferric carboxylmethyl konjacglucomannan gel microspheres (CMKGM-Fe) were prepared by cross-linking carboxyl methyl konjac glucomannan (CMKGM) with ferric ions (Fe3+). The complex of CMKGM-Fe/benzoic acid was characterized by IR spectroscopy. The adsorption capacity of CMKGM-Fe for benzoic acid was studied by UV–vis spectroscopy. Several parameters including the adsorption time, temperature, microsphere size, and the concentrations of CMKGM, FeCl3, and benzoic acid were investigated. The results showed that adsorption equilibrium could be established in about 11 h. When the temperature was 298 K, the CMKGM concentration was 1.5 % (w/v), the mass ratio of Fe3+ was 2.5 % (w/v), and the initial concentration of benzoic acid was 1000 mg·L–1 and the adsorption capacity attained 0.4954 mmol·g–1. According to the adsorption isotherms of benzoic acid on CMKGM-Fe, the thermodynamic parameters of adsorption process were calculated. The experimental data were fitted with the Freundlich equation, and it was found that the equation was suitable for the study of the investigated adsorption system. The entropy value of the system is negative, and cooling is beneficial for the adsorption, suggesting that the system is a spontaneous exothermic process.

Preparation and Characterization of Konjac Glucomannan Gel

Konjac glucomannan (KGM) gel was prepared by alkali catalyzed in aqueous solutions. The structure of the KGM gel was characterized by Fourier transform infrared (FTIR) spectroscopy and wide angle X-ray diffraction (WAXRD). The gel point of KGM solutions was determined by steady state fluorescence method and It was observed that the gel point of the KGM solutions depend on the concentration of KGM, pH value and temperature effectively. The results showed that the molecular chain structure of KGM gel is more regular than that of the pure KGM.

Effect of alkalis on konjac glucomannan gels for use as potential gelling agents in restructured seafood products

Four dispersions of 3% glucomannan in water, deacetylated with 5% 0.6 N and 1 N KOH (lots L1 and L2) and 0.6 N and 1 N NaOH (lots L3 and L4) as gelling agents, were evaluated for use in raw restructured seafood products. Several properties (pH, moisture content, water binding capacity, cooking loss and lightness) together with puncture data (breaking force and breaking deformation) were determined after 1 and 10 days of chilled storage at 5 °C. All these data were analyzed together with different viscoelastic parameters obtained at small amplitude oscillatory strain (SAOS) after 1 day of chilled storage, showing that L1 and L4 samples were the most suitable gels for incorporation in raw restructured fish products. In both cases the highest stress ( σ max) and strain ( γ max) amplitude values were found in the linear viscoelastic (LVE) range; however, L1 showed both high strain amplitude and breaking deformation values. Moreover, creep and recovery (transient) data showed that L1 was the most time-stable gel with the highest elasticity and the lowest relaxation exponent ( n). L4 gel showed strong rigidity, i.e. the highest values of breaking force and storage moduli ( G′) and the highest n value, making it less gel-like. Both L1 and L4 gels became significantly less gel-like over 10 days of chilled storage due to the loss of gel strength ( S) and a noticeable increase of n. These chilled storage effects were more intense in L4 than in L1.

Molecular Dynamics Simulations of the Interactions Between Konjac Glucomannan and Soy Protein Isolate

The interactions between konjac glucomannan(KGM) and soy protein isolate (SPI) were studied with the method of molecular dynamics simulation. Part representative structures segments of KGM and SPI were used as mode, and the force-field was FF03. The stability and sites of KGM/SPI interactions in water were researched at 363 K with the following results: the potential energy (EPOT) of the mixed gel dropped, while that of single KGM gel increased. The surface area (SA) of KGM in the mixed system was decreased to 401.41 from 1 267.54 Å 2, and that of SPI to 484.94 from 1 943.28 Å 2. The sum potential energy of KGM and soy protein in the mixed system was decreased to −13 402.41 from −5 768.56 kcal mol −1. The variations of two parameters showed that the stability of compound gel KGM/SPI was improved, which was consistent with the previous studies. The sites of interactions in the mixed gel were the −OH groups on C(2) in KGM mannose and glucose, and the amide linkage group on Histidine, Asparagine and Leucine in SPI. The hydrogen bond was formed directly or indirectly by the bridge of waters.

Konjac Glucomannan as a Carrier Material for Time—Temperature Integrator

Hardness, springiness and water retention of konjac glucomannan gel (g-KGM) as a novel carrier material for time-temperature integrator (TTI) in aseptic processing were determined and compared with those of sodium alginate gel (g-SA). Hardness of both g-KGM and g-SA increased with temperature: values of g-SA were significantly higher (p < 0.05) than those of g-KGM at all temperatures. No significant difference in springiness between g-KGM and g-SA from 40 °C to 90 °C and significant differences (p < 0.05) between 100 °C and 140 °C were found. Water retention property of g-KGM was lower than that of g-SA between 60 °C and 100 °C, but much higher between 100 °C and 140 °C. Heat transfer tests performed on g-KGM alone as well as on g-KGM as a carrier, embedded with TTI, α-amylase as an integrator, indicated that g-KGM was suitable for industrial ultrahigh temperature sterilization test.

Rheological properties of konjac glucomannan/SiO2/organic-borate gels

A series of thermoreversible konjac glucomannan gels crosslinked by organic borate were prepared. Required amount of hydrophilic SiO2 was added into the konjac glucomannan solutions before the crosslinking reaction. The gel network was formed through the crosslinking reaction between borate ions dissociated from organic borate and the cis-diol hydroxyl groups on the mannose units of polysaccharide chains. The rheological properties of the complex gels were studied by dynamic viscoelastic measurement. The gelation kinetics of the complex gels was studied and the critical gelation points of the gels were exactly determined by the Winter-Chambon criterion. The effects of temperature and composite ratio on the shear storage modulus (G′), the loss modulus (G″) and the sol-gel transition points were investigated.

Gelation of konjac glucomannan crosslinked by organic borate

A series of thermoreversible konjac glucomannan gels crosslinked by organic borate were prepared. The gel network was formed through the crosslinking reaction between borate ions dissociated from organic borate and the cis-diol hydroxyl groups on the mannose units of polysaccharide chains. The rheological properties of the complex gels were studied by dynamic viscoelastic measurement. The gelation kinetics of the gels were studied and the critical gelation points of the gels were exactly determined by the Winter–Chambon criterion. The effects of temperature and composite ratio on the shear storage modulus ( G ′), the loss modulus ( G ″), and the sol-gel transition points were investigated. The critical gel-sol temperatures of the complex gels were successfully elucidated by Winter–Chambon criterion. The effect of crosslinking density on the critical gelation temperature and the elasticity of the gels were discussed.

Direct determination of Cd and Pb in gel forming konjac samples by enzymatic hydrolysis assisted slurry sampling graphite furnace atomic absorption spectrometry

Konjac flour is a gel-forming edible dietary fiber used as a food and a food additive. A method of slurry sampling after an enzymatic hydrolysis pretreatment was developed for the determination of Cd and Pb in refined konjac flour, by graphite furnace atomic absorption spectrometry (GFAAS). Konjac flour, extracted from the tuber of Amorphophallus konjac, contains high amounts of konjac glucomannan (KGM). KGM is a long chain polysaccharide and easily forms a gel in aqueous solution, which inhibits direct sample introduction into the graphite furnace. After an enzymatic hydrolysis pretreatment, the KGM gel is not formed and the flour was made into slurry for GFAAS analysis. Conditions for α-amylase based enzymatic hydrolysis were optimized. The vaporization behavior of Cd and Pb in the slurry of hydrolysis solution was investigated thoroughly. Calibrations against aqueous standards and slurry standards were compared and good agreement has been shown. The detection limits were 3.0 ng g−1 Cd and 27.8 ng g−1 Pb for solid konjac flour and the characteristic masses (mc) were 2.0 pg Cd and 9.0 pg Pb, respectively. The method has been applied to the determination of Cd and Pb in commercial refined konjac flour.

Preparation of konjac glucomannan hydrogels as DNA-controlled release matrix

In this study, hydrogels for DNA-controlled release was prepared with konjac glucomannan (KGM), a water-soluble non-ionic polysaccharide, by means of deacetylated reaction and physically cross-linking method under mild conditions. The properties of the KGM hydrogels were analyzed by FTIR spectra and scanning electron microscopy (SEM). The integrality of the released DNA was investigated by circular dichroism (CD). The DNA release kinetics was performed using the DNA-loaded KGM gels in buffer solutions of pH 7.4 at 37 ± 0.5 °C. Peppas model and Higuchi model were used to analysis the DNA release mechanism; the data indicated that the DNA release can be controlled by changing the preparation conditions and the structure parameters of the gels. This study suggested that the KGM hydrogels have a potential use for advanced controlled release.

In vitro dynamic adsorption properties of sulfated glucomannan gel beads

Sulfated konjac glucomannan gel beads(KGMSB) were prepared, its dynamic adsorption abilities for blood low-density lipoprotein and very low density lipoprotein cholesterol(LDL+VLDL-C) and the effect on hemorheology were studied. Konjac glucomannan(KGM) was used as raw material, after cross-linked by epichlorohybrin solution, and was then prepared into gel beads, hardened, and sulfated, final product KGMSB was obtained. The structure of KGMSB was observed by SEM. SEM analysis shows that KGMSB possesses cross-linked porous network structure. In vitro dynamic adsorption indicates that the adsorption rate for total cholesterol(TC), low-density and very low-density lipoprotein cholesterol(LDL+VLDL-C), high-density lipoprotein cholesterol(HDL-C) of KGMSB are (62.10±7.96)%, (63.42±8.27)%, (40.25±5.73)% (n=6), respectively. The ratio of HDL-C/LDL-C is increased by (30.12±7.07)%. The hemorheology studies show that whole blood viscosity and plasma viscosity are changed significantly (p<0.05). KGMSB can selectively adsorb LDL+VLDL-C from the whole blood, it can also reduce the blood viscosity and modulate hemorheology properties. KGMSB is a potential material to be developed into a novel blood LDL adsorbent.

Effect of deacetylation rate on gelation kinetics of konjac glucomannan

Effect of deacetylation rate on the gelation behaviors on addition of sodium carbonate for native and acetylated konjac glucomannan (KGM) samples with a degree of acetylation (DA) range of 1.38–10.1 wt.% synthesized using acetic anhydride in the presence of pyridine as catalyst was studied by dynamic viscoelastic measurements. At a fixed alkaline concentration ( C Na), both the critical gelation times ( t cr) and the plateau values of storage moduli ( G ′ sat ) of the KGM gels increased with increasing DA. While at a fixed ratio of alkaline concentrations to values of DA ( C Na/DA), the similar t cr and G ′ sat values independent of DA were observed. On the whole, increasing KGM concentration or temperature shortened the gelation time and enhanced the elastic modulus for KGM gel. The effect of deacetylation rate related to the C Na/DA on the gelation kinetics of the KGM samples were discussed.

Effect of degree of acetylation on gelation of konjac glucomannan.

Effect of the degree of acetylation (DA) on the gelation behaviors on addition of sodium carbonate for native and acetylated konjac glucomannan (KGM) samples with a DA range from 1.38 to 10.1 wt % synthesized using acetic anhydride in the presence of pyridine as catalyst was studied by dynamic viscoelastic measurements. At a fixed alkaline concentration (CNa), both the critical gelation times (tcr) and the plateau values of storage moduli (G'sat) of the KGM gels increased with increasing DA, while at a fixed ratio of alkaline concentrations to values of DA (CNa/DA), similar tcr and values independent of DA were observed. On the whole, increasing KGM concentration or temperature shortened the gelation time and enhanced the elastic modulus for KGM gel. The effect of deacetylation rate related to the CNa/DA on the gelation kinetics of the KGM samples was discussed.

Changes in Temperature, Texture, and Structure of Konnyaku (Konjac Glucomannan Gel) During High-pressure-freezing

: To determine the effects of high-pressure-freezing, changes in temperature, texture, and structure of konnyaku (a gel with high water content) were measured during freezing for 60 min at 0.1 to 700 MPa and -20 °C. During freezing at 0.1, 100, 500, 600, and 700 MPa, exothermic peaks were detected (konnyaku froze). However, at 200 to 400 MPa, exothermic peak was not detected and temperature rose when pressure was released at -20 °C; the supercooled konnyaku froze by pressure-shift-freezing. The coarse gel network observed in unfrozen konnyaku was compressed by freezing due to formation of ice crystals. The rupture stress increased and strain decreased in all frozen konnyaku. High-pressure-freezing was ineffective in improving the texture of frozen-then-thawed konnyaku.

Liquid crystalline, rheological and thermal properties of konjac glucomannan

Konjac glucomannan (KGM) exhibited liquid crystalline (LC) behaviour in aqueous solutions above 7% (w/w) concentrations as was determined by polarized optical microscopy and circular dichroism. The rheological properties of the concentrated LC solutions of KGM exhibited pseudoplastic behaviour. The fibrous extrudates retained a significant degree of flow-induced orientation as was determined by wide angle X-ray scattering, thereby indicating potential applications of KGM as fibres and films. Differential scanning calorimetry experiments showed that a significant degree of interaction occurred between KGM and water and that the KGM gels produced in our study cannot be classified as thermoreversible.

A mixed system composed of different molecular weights konjac glucomannan and κ-carrageenan. II. Molecular weight dependence of viscoelasticity and thermal properties

Rheological and thermal properties for 5:5 mixed gels of konjac glucomannan (KGM) with five different molecular weights and κ-carrageenan (CAR) were studied. Molecular weight distribution was analysed by gel permeation chromatography (GPC). Dynamic and static viscoelastic moduli for the mixed gels were much smaller than those for gels of CAR alone and became larger with increasing molecular weight of KGM. Gel—sol transition for mixed systems with total gum content 1.5% w/w occurred at the temperatures between the transition temperature for 0.75% w/w CAR and that for 1.5% w/w CAR. Gel-to-sol and sol-to-gel transition temperatures for the mixed systems were slightly increased with increasing molecular weight of KGM in the mixture observed in differential scanning calorimetry (DSC). One exothermic peak was observed in cooling DSC curves, while two endothermic peaks appeared in heating DSC curves for 5:5 mixed systems. The intensity of the lower peak increased with increasing KGM proportion in the mixture and with increasing molecular weight of KGM at a given mixing ratio. This fact confirms that the mixed gels involve two crystalline regions: some are made by CAR molecules in the helical structure and others are formed by the interaction between helical CAR and KGM. On heating, the latter is broken at a lower temperature and then the former melts at a higher temperature. The junction zone formed by CAR and KGM is easily made in a gel containing KGM with a higher molecular weight or in a higher ratio to CAR, or a system of lower total gum content.

Stoichiometry and Conformation of Xanthan in Synergistic Gelation with Locust Bean Gum or Konjac Glucomannan: Evidence for Heterotypic Binding

Synergistic gels of xanthan or deacetylated xanthan (DX) with locust bean gum (LEG) or konjac glucomannan (KM) melt and set at similar to 60 degrees C, with no thermal hysteresis, Gelation occurs with the xanthan component in either its ordered or its disordered form and, with KM as cosynergist, is accompanied by large enthalpy changes (Delta H) in DSC. Gel modulus (G') and Delta H increase linearly with increasing ratio of KM:DX up to similar to 1:1, with little further change at higher ratios. Liquid-like character (tan delta) passes through a sharp minimum at about the same composition. Mixed gels of KM with unmodified xanthan show similar behavior, but the maximum value of Delta H is lower, and the proportion of KM required to achieve this maximum is higher. The heat changes (per gram of xanthan or DX) depend only on mixing ratio, not on total concentration, arguing strongly for stoichiometric binding rather than an exclusion mechanism. With LEG in place of KM, the sol-gel transition is much wider and gives no discernible peaks in DSC. The minimum in tan delta with varying composition, however, is still evident, again arguing for a binding process, and the moduli are higher (similar to 3x). Gels incorporating KM show evidence of structural rearrangement after their initial formation (maxima in the temperature dependence of G''; shoulders in tan delta and in DSC); no such effects are seen for LEG. In the light of previous X-ray diffraction studies in the condensed phase, it is suggested that initial gelation involves heterotypic junctions between xanthan or DX and KM or LEG, with both components in a 2(1) conformation, but that junctions involving KM convert to a more compact 6-fold arrangement at lower temperature.

A mixed system composed of different molecular weights konjac glucomannan and kappa carrageenan: large deformation and dynamic viscoelastic study

Rheological properties of mixed gels of konjac glucomannan (KGM) of four different molecular weights with kappa-carrageenan (CAR) were studied by dynamic viscoelastic measurements and tensile testing. Both storage and loss moduli for sol and gel state mixtures containing higher molecular weight KGM were highest. However variation in molecular weight of KGM produced little effect on the gel-to-sol and sol-to-gel transition temperatures of the mixtures. Two systems containing KGM of lower molecular weights showed almost the same stress—strain curves in tensile testing. The breaking stress and the breaking strain for mixed gels became larger with increasing molecular weight of KGM, and the difference was larger than that observed in the dynamic viscoelasticity measurements. It was suggested that weak junction zones are created by the addition of KGM and that the number of weak junction zones and the contour length of flexible chains connecting these weak junction zones increase with increasing molecular weight of KGM.