Comparison of two methods for stress relaxation data presentation of solid foods

Abstract

Published exponential relaxation equations, derived from Maxwellian models, were used to generate data for linear representation in the form ofP(0) ·t/(P(0) —P(t)) =k ₁ +k ₂t whereP(t) is the decaying parameter (force, stress or modulus),P(0) its initial value (att = 0) andk ₁ andk ₂ constants. The computer plots indicated that the fit of this normalized and linearized form was excellent for equations containing at least three exponential decay terms. The fit was not as good for some of the two-term exponential equations mainly due to the lack of accurate account for the initial stage of the relaxation process. In all the cases, however, the linear representation could clearly reveal the general rheological character of the analysed materials in terms of the relative degree of solidity.