INFLUENCE OF TEMPERATURE ON THE DYNAMIC AND STEADY-SHEAR RHEOLOGY OF PECTIN DISPERSIONS

• Type: Article in International Scientific Journal
• Date: 1994

Authors

DASILVA, JAL (Author) Other; Maria do Pilar Gonçalves (Author) FEUP; RAO, MA (Author) Other

Journal

Title: Carbohydrate Polymers

Vol. 23

Pages: 77-87

ISSN: 0144-8617

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 47 Citations

ISI Web of Science

Scopus - 64 Citations

Scientific classification

FOS: Engineering and technology > Other engineering and technologies

Other information

Authenticus ID: P-001-KM3

Resumo (PT): The influence of temperature on the dynamic and steady-shear rheology of ionic polysaccharides, high-methoxyl and low-methoxyl pectins, has been studied and compared with the behaviour of locust bean gum, a virtually neutral biopolymer. Using the time-temperature superposition principle, the rheological parameters were reduced to an arbitrary reference temperature. Activation energies wore calculated and their dependence on temperature and shear rate analysed. Concerning the viscosity dependence on temperature, two approaches have been considered: one associated with the theory of absolute reaction rates leading to an Arrhenius type equation, and the other associated with the frce volume theory, expressed by the Williams-Landel-Ferry equation. The difficulties encountered in the superposition of the dynamic properties of the pectin disper-sions, the high activation energies, yield values and elastic plateau at low oscilla-tory frequency, are consistent with a macromolecular organisation of these polymers dominated by important aggregation phenomena, which could be attributed to important intermolecular interactions like hydrogen bonding and hydrophobic interactions, especially in conditions of low degree of ionization of the carboxylic groups.

Abstract (EN): The influence of temperature on the dynamic and steady-shear theology of ionic polysaccharides, high-methoxyl and low-methoxyl pectins, has been studied and compared with the behaviour of locust bean gum, a virtually neutral biopolymer. Using the time-temperature superposition principle, the theological parameters were reduced to an arbitrary reference temperature. Activation energies were calculated and their dependence on temperature and shear rate analysed. Concerning the viscosity dependence on temperature, two approaches have been considered: one associated with the theory of absolute reaction rates leading to an Arrhenius type equation, and the other associated with the free volume theory, expressed by the Williams-Landel-Ferry equation. The difficulties encountered in the superposition of the dynamic properties of the pectin dispersions, the high activation energies, yield values and elastic plateau at low oscillatory frequency, are consistent with a macromolecular organization of these polymers dominated by important aggregation phenomena, which could be attributed to important intermolecular interactions like hydrogen bonding and hydrophobic interactions, especially in conditions of low degree of ionization of the carboxylic groups.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 11