Food Rheology using Dynamic Mechanical Analysis; A short review

Abstract

An ideal elastic material will deform finitely and recover its original shape and size upon the removal of the applied deforming load. On the other hand an ideal fluid will deform and continue to deform as long as the deforming load is applied, and finally the material doesn’t recover from that deformation even when the load is removed. These two responses are termed as ‘elastic’ and ‘viscous’ respectively. Most materials, exhibits an intermediate viscous and elastic behavior and are referred to as “viscoelastic”. A good example of such materials are polymers. In addition almost all foods, both liquid and solid, belong to this group. The viscoelasticity of materials can be determined by transient or dynamic methods. The transient methods are two pronged; stress relaxation which is the application of constant and instantaneous strain and measuring decaying stress with respect to time and creep which is the application of constant and instantaneous stress and measuring increasing strain with time. The transient methods are easy to perform, however, they are limited in the sense that the material response cannot be determined as a function of frequency. The dynamic methods are performed applying a small sinusoidal strain (or stress) and measuring the resulting stress (or strain). Due to the enormous list of advantages of performing dynamic tests, the method has been very popular in polymer studies for many years. This brief review demonstrates that the method has found a now increasing usage, especially in the last two decades, in studies of food, what has been referred to as Food Rheology.