Chapter 6 - Nonlinear Rheology of Fats Using Large Amplitude Oscillatory Shear Tests

Abstract

Rheology provides information on structure, interaction forces and associated elasticity and plastic flow of structural elements. Understanding the relationship between structure and rheology is crucial for the design of fat products with tailored mechanical functionality. Currently, great strides have been made toward establishing the link between linear viscoelasticity and the microstructure of fat crystal networks. On the other hand, less effort has been devoted in rationalizing their nonlinear (yielding) behavior which of paramount importance as shown in this chapter. This chapter briefly revisits conventional small amplitude oscillatory shear (SAOS) and presents a succinct account of large amplitude oscillatory shear (LAOS). The contents of the chapter are divided into linear and nonlinear viscoelasticity theory, quantitative methods for data analysis and interpretation with emphasis on the Chebyshev stress decomposition method, experimental considerations for collection, processing, and analysis of data obtained from LAOS experiments, and results from two different samples (fat crystal networks and fat-filled gels). The findings from the case studies highlight the value of the LAOS technique in understanding material functionality.