The rheological properties of apple pectins with different degrees of side branches were investigated in terms of the zero-shear viscosity (η0), the shear rate dependence of viscosity and the superposability of rheological data to a variety of generalization curves such as ηsp versus c[η], ηsp versus cMw, η η0 versus γ ̇ γ ̇0·8 and η η0 versus γ (η0 - ηs)Mw/cRT. Increase in branching of pectins resulted in higher η0 and increasing shear rate dependence of viscosity. The gradients of ηsp.0 versus c [η] in the concentrated region (c [η] > c* [η]) were dependent upon the degree of branching, i.e. the higher the branching, the higher the gradients, whereas there was no significant difference in the dilute region (c [η] < c* [η]) irrespective of the degree of branching. Pectins with a low degree of branching displayed better superposition in η η0 versus γ ̇ γ ̇0·8 and η η0versus γ (η0 - ηs)Mw/cRT curves when compared to the sample with more branches. Circular dichroism (CD) studies of pectins showed that the conformation of pectin molecules was not affected by the degree of branching. It is concluded that side branches of pectins can result in significant entanglements in concentrated solutions.
Bibliographical noteFunding Information:
This is paper D-10411-5-89 of the New Jersey Experimental Station. This work was supported by the Campbell Soup Co. and their support is greatly appreciated.
All Science Journal Classification (ASJC) codes
- Organic Chemistry
- Polymers and Plastics
- Materials Chemistry