Influence Of Cyclodextrins On The Gel Properties Of κ-Carrageenan And Its Applications

The impact of cyclodextrins on the gelling properties and gel temperature were studied by added different concentrations α-CD,β-CD,γ-CD,HP-β-CD and M-β-CD into κ-carrageenan,and then the paper explored the application of κ-carrageenan and β-CD in sugar-free gel preliminarily.The effects of κ-carrageenan concentration and four types of ions concentration on the properties of κ-carrageenan gels were studied by means of texture and rheological analysis,including K⁺,Na⁺,Mg²⁺ and Ca²⁺.The results show that with κ-carrageenan concentration increased,the hardness,gumminess and chewiness were enhanced,and the elasticity increased first and then decreased,however,the cohesiveness of gel was no significantly affected by theκ-carrageenan concentration.K⁺,Mg²⁺ and Ca²⁺ led to a stronger gel,but when ions concentration more than 0.2%,the gel brittleness increases and the elasticity decreases.However,the gels texture properties at Na+ concentrations from 0.1% to 0.5% had no significant change.The order of influenced of four kinds of salt ions on the gel properties of κ-carrageenan was K⁺>Ca²⁺> Mg²⁺> Na⁺.Higher K⁺ concentrations led to higher gelling temperature,while with Ca²⁺,Na+ and Mg²⁺ concentrations increased,the gelling temperatures were increased,but the temperature rises slowly.When the salt ions concentrations were 0.2%,the order of influenced of ions on gel viscosity of κ-carrageenan was Ca²⁺> Mg²⁺> K⁺ >Na⁺.Through the study of the properties of κ-carrageenan/cyclodextrins/water gel,it was found that cyclodextrins had a significant effect on the texture of κ-carrageenan gel.α-CD,β-CD,γ-CD parent cyclodextrins reduced the gel hardness,while HP-β-CD and M-β-CD increased with the increase of hardness first and then decreased slightly.Cyclodextrins enhance the gel elasticity,chewiness and adhesiveness,while cohesiveness is not significantly affected.The rheological results show that cyclodextrins has a promoting effect on the gelation temperature of κ-carrageenan.The apparent viscosity of 5 cyclodextrins（mass fraction 3%）decreased with the increase of shear rate.The apparent viscosity was in the order of κ-carrageenan >β-CD >α-CD >γ-CD > HP-β-CD > M-β-CD.The results of FT-IR test showed that the network structure of the κ-carrageenan/cyclodextrins/water gel system was formed,based on the network structure of κ-carrageenan,and between κ-carrageenan and cyclodextrins molecules exist interaction.The results of TGA showed that the weight loss rate of κ-carrageenan was 39.69%,the decomposition temperature was about 223.17 ℃,and the thermal stability of κ-carrageenan/cyclodextrins/water gel system was significantly improved.SEM results show that the structure of the cyclodextrins are dispersed in the framework of the κ-carrageenan,and the gel wall layer becomes smooth.The results of freeze-thaw stability test showed that the water content of κ-carrageenan/cyclodextrins/water gel was increased from 9% to 56%.The optimum process of preparing sugar-free edible gel was studied by single factor test and response surface test using kappa carrageenan,β-CD,xylitol and citric acid as raw materials.The optimal conditions for the preparation of sugar-free gel were as follows: the amount of κ-carrageenan was 0.7%,β-CD was 1.92%,xylitol was about 16.87%,and citric acid was about 0.2%,and at this point the hardness and elasticity of the sugar-free gel were 1.70 N and 12.065 mm.κ-carrageenan/β-CD gel sugar-free edible gel preparation,effects of κ-carrageenan on sugar-free gel hardness and elasticity were significantly（P<0.05）,and the amount of β-CD,xylitol,citric acid on the hardness and springiness of the gel had no significant effection.While the freeze-thaw stability of sugar free gel improved from 20% to 30%.