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RHEOLOGICAL CHARACTERIZATION OF LOW‐METHOXYL PECTIN GEL BY NORMAL CREEP AND RELAXATION
Author(s) -
GROSS M. O.,
RAO V. N. M.,
SMIT C. J. B.
Publication year - 1980
Publication title -
journal of texture studies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.593
H-Index - 54
eISSN - 1745-4603
pISSN - 0022-4901
DOI - 10.1111/j.1745-4603.1980.tb00326.x
Subject(s) - rheology , pectin , creep , stress relaxation , materials science , relaxation (psychology) , elastic modulus , viscosity , universal testing machine , modulus , texture (cosmology) , chemistry , composite material , biochemistry , ultimate tensile strength , psychology , social psychology , image (mathematics) , artificial intelligence , computer science
Fourteen low‐methoxyl pectins were used to prepare a 30% sucrose gel with a final pectin concentration of 0.8% and an added calcium content of 25 mg Ca ++ /g pectin. The texture of each gel was evaluated using three descriptors: firmness, coarseness, and graininess. The relaxation behavior of the 14 gels, under a constant strain, was monitored using an Instron universal testing machine. The data were best defined by an equation that is represented by two Maxwell bodies in parallel. The elastic moduli and relaxation times of this model ranged, between gels, from 2881 Pa to 5487 Pa and from 4.1 s to 908 s, respectively. An apparatus constructed in this laboratory was used to measure the creep behavior of the gels under constant stress. The normal creep behavior of the 14 gels was best defined by the Burger's Model. The elastic moduli and viscous constants of this model ranged, between gels, from 3937 Pa to 15,342 Pa and from 20,300 Pl to 40,100 Pl, respectively. The relaxation modulus, E 1 , was the most sensitive for distinguishing significant differences between the gels. Several significant correlations were found between rheological, chemical and textural parameters.