Rheological properties of natural low-methoxyl pectin extracted from sunflower head

• The extracted SFHP is linear polysaccharide with narrow polydispersion.
• Huggins plot indicated a stiff rod-like conformation of SFHP in dilute solution.
• Increasing of pectin concentration resulted in rapid increase of solution viscosity.
• Aggregation of pectin became obvious by lowering pH to below 3.0.

Rheological properties of natural low-methoxyl sunflower pectin have been investigated. Sugar composition and molecular parameters of SFHP were characterized. The Mw and Mn of SFHP is 605.6 kDa, 111.0 kDa, respectively, thereby giving a moderate polydispersion index of 5.50. Huggins plot indicated a stiff rod-like conformation of SFHP in dilute solution. Dilute SFHP solution (<1.0%, w/w) had low viscosity due to lack of interactions. Increasing of pectin concentration resulted in rapid increase of solution viscosity since SFHP has large hydrodynamic size. The aggregation of pectin became obvious by lowering pH to below 3.0. In pH range from 4.0 to 7.0, there is no difference in rheological behaviors of 1.0% SFHP solution. When heated, viscosity of SFHP solutions gradually decreased and attained equilibrium state at over 60 °C. In the case of 3.0% (w/w) SFHP solution, the network structure has been formed and the solution presented good resistance to environmental change.

Increasing concentration led to rapid and significant increase of initial viscosity since SFHP has a high molecular weight. A sudden viscosity increase when SFHP concentration varied from 2.5% to 3.0% indicated strong aggregation of pectin chains.Figure optionsDownload as PowerPoint slide