Gelation of κ-carrageenan/Konjac glucommanan compound gel: Effect of cyclodextrins

The impact of cyclodextrins (CDs) on physical properties of the compound gel of kappa-carrageenan/konjac glucommanan (KC/KGM) was investigated by texture profile analysis (TPA), compression modulus test, freeze-thaw stability test, scanning electron microscopy (SEM) and X-ray diffraction (XRD). TPA results showed that CDs 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 CDs concentrations, then gradually decreased at higher CDs concentrations. Cohesiveness, gumminess and chewiness showed similar tendency as the hardness. However, influence of CDs on gel springiness was slight. Compressive experiment indicated that the CDs 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 CDs, about 10% more water was preserved after the first freeze-thaw cycle. SEM results showed that the microstructures of the compound gels containing CDs were much denser with smaller voids. XRD results indicated that the crystallization peaks of the compound gels decreased after CDs were added. The exclusion of CDs 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. CDs improved the synergistic interaction between KC and KGM polysaccharides. The influence of methyl-beta-cyclodextrin (M-beta-CD) on the formation and characteristics of KC/KGM compound gel was the most significant among all the selected CDs.