Strain Dependence of the Uniaxial Compression Response of Vegetable Shortening

Many soft food materials, including vegetableshortening, exhibit complex rheological behavior. For short-ening, a precise determination of rheological behavior isnecessary to understand its functionality as a food ingredient.Commercial vegetable shortening was subjected to mono-tonic and cyclic uniaxial compression tests at a wide range ofloading rates. The elastic modulus determined from unloadingwas a function of strain, varying between 740 kPa in theshortening’s strain hardening region to 220 kPa at large strainwhere perfect plasticity had developed. Visual analysis ofshortening specimens during the compression process showedthat a rate-dependent stress overshoot was attributable to thedevelopment of a shear band following strain hardening. Anelastoviscoplastic constitutive model was developed to definethe complex rate-dependent compression response of vege-table shortening. Using the fundamental parameters obtainedfrom the different types of compression tests, the proposedmodel accurately predicted the uniaxial compression responseof vegetable shortening over a wide range (three decades) ofcompression rates. A model with predictive capabilities oflarge strain properties is desirable because shortening is sub-ject to large strain in essentially all applications.