Gelling Properties of High-acyl Gellan Gum Based on the Stress Relaxation Theorem
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Abstract:
In this study, the stress-relaxation model was used to examine the effects of monovalent (K+ and Na+) and divalent (Ca2+ and Mg2+) cations on the gelling properties of high-acyl gellan gels. The results suggested that the stress relaxation behavior of high-acyl gellan gels fitted well with Peleg’s empirical model. The types and concentrations of cation had significant effects on the stress relaxation behavior of high-acyl gellan gels. The values of equilibrium modulus (EA) formed a saddle-shape curve with increasing cation concentration and correlated positively with gel hardness (R = 0.943 to 0.983), indicating that EA could be used to characterize gel strength. The gels formed by divalent cations showed greater gel strength than those formed by monovalent cations. At constant concentrations of cation, gellan gels formed by Na+ were stronger than those formed by K+, whereas gels formed by Ca2+ were stronger than those formed by Mg2+. When subjected to 16,000 ×g centrifugal force for 10 min, all high-acyl gellan gels exhibited water-holding capacity of more than 95%. In addition, the water-holding capacity of high-acyl gellan gels was less sensitive to changes in K+, Na+, Ca2+, and Mg2+ concentrations. The mechanism of stress relaxation appeared to be associated with the movement of physical cross-links in the gel matrix.
