Effect Of Cyclodextrins On The Gelling Properties Of Carrageenan/Konjac Glucommanan And Its Applications

Compound gel is widely used in food industry,which has synergistic effect,and the resulting gel has the characteristics of less required raw materials,high gel hardness,moderate viscoelasticity,uniform and smooth gel surface and so on.However compound gel have many weaknesses,including poor stability and high syneresis rate.The impact of cyclodextrins?CD?on gel properties of the compound gel of?-carrageenan/konjac glucommanan?KC/KGM?was investigated by physical properties analysis,rheological analysis,thermogravimetric analysis,fourier transform infrared analysis,high field NMR analysis and X-ray diffraction?XRD?.The impact of CD on physical properties of the KC/KGM compound gel was investigated by texture profile analysis?TPA?,compression modulus test,rheological analysis,scanning electron microscopy?SEM?and freeze-thaw stability test.TPA results showed that CD had remarkable influence on mechanical properties of the compound gel.In concentration range of 0.5%-1.5%?w/w?,hardness was strengthened with the increase of CD concentrations,then gradually decreased at higher CD concentrations.Cohesiveness,gumminess and chewiness showed similar tendency as the hardness.However,influence of CD on gel springiness was slight.Compressive experiment indicated that the CD increased the compressive elastic modulus?S?of the compound gel and improved the deformation resistance of the gel network.In the freeze-thaw stability test,stability of the compound gels was obviously improved after adding CD,about 10%more water was preserved after the first freeze-thaw cycle.SEM results showed that the microstructures of the compound gels containing CD were much denser with smaller voids.In the sol state,the rejection of polysaccharide chains to CD makes the KC/KGM composite solution form a denser network structure after cooling,which is more conducive to the texture of the gel and the improvement of freeze-thaw stability.The effect of CDs on the thermodynamic properties of the KC/KGM compound gels was investigated and it was found that the thermodynamic characteristics of the compound gels with CDs were significantly improved.Thermogravimetry found that the weightlessness rate of KC/KGM compound gel was higher than that of KGM and KC.The increase of decomposition temperature of the compound gels indicated that the decomposition of the mixed gels required higher energy than that of the pure KC.With the addition of CDs,more short-walled networks were formed,the crystallization area decreased and the weight loss rate increased.The higher decomposition temperature of KC/KGM compound gels indicated that higher energy was needed to decompose the components,which was represented by the higher thermal stability of the KC/KGM compound gels.Temperature sweep results showed that CD could increase the gel temperature(T_gel)and sol temperature(T_sol)of KC/KGM compound,which could beneficial to the solidification and forming of gel food and the stability of product.The gelation mechanism of compound gels with different CDs and KC/KGM compound gels was investigated by means of FTIR,¹HNMR and XRD.The FTIR experiment showed that the hydroxyl vibration peak of the compound gel shifted to the lower wave number with the addition of CD,indicating that the hydrogen-bond interaction between the compound gel and the CD molecules was strengthened,which showed that the strength and elasticity of the blend gel were enhanced.The results of¹HNMR showed that the compound gel of KC/KGM had a lower chemical displacement than those of KC and KGM,indicating that the hydrophilic environment and hydrogen bonds were increased and the network structure was closer.XRD results indicated that the crystallization peaks of the compound gels decreased after CD was added.The exclusion of CD from the polysaccharides chains in the sol state led the KC/KGM compound solution to form a denser network after cooling and benefited the texture and freeze-thaw stability of the formed gel.Edible gelatin using KC/KGM,CD,sucrose,vanillin as raw materials and potassium chloride as gel additives were studied.The best process for edible gelatin was optimized by orthogonal experiment and were analyzed by texture and freeze-thaw stability experiment.The optimum conditions for preparation of edible gel were as follows:CD content:1.5%,sucrose content:17%,vanillin content:0.015%.The hardness and elasticity of edible gels were 276.747 N and 0.936,reaching the level of texture characteristics of commercially available jellies.The freeze-thaw stability of edible jellies was significantly improved,about 5%higher than that of commercial jellies.