Effect of Different Mannuronic Acid/Guluronic Acid Ratios on the Rheological Properties of Sodium Alginate
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Abstract:
The effect of varying mannuronic acid/guluronic acid static (M/G) ratios on the static and dynamic rheological, gelling, and gel stress-relaxation properties of sodium alginate (AGNa) was studied using a dynamic rheometer. The results showed that the M/G ratio significantly influenced the static rheological properties of AGNa within the medium viscosity range, but the effect was not significant within the low viscosity range. AGNa exhibited the flow characteristics of pseudoplastic fluid at low pH and Newton fluid at high pH. The effect of temperature on the apparent viscosity of AGNa solution was in accordance with the Arrhenius model and flow activation energy positively correlated with the M/G ratio. Within the same viscosity range, an increase in M/G ratio was accompanied by prolongation of AGNa gelation time (tG), decrease in gelation temperature, and a downward trend in stress and stress-relaxation modulus of AGNa gel. A high M proportion favored formation of a viscous component-based fluid system, while high G proportion benefited the formation of elastic component-based gel system.
