ReviewThe comparison of LAOS behavior of structured food materials (suspensions, emulsions and elastic networks)

- Large amplitude oscillatory shear properties (LAOS) of tomato paste, mayonnaise, soft and hard wheat flour were reviewed.
- All food materials showed an intracycle strain hardening and strain softening.
- Lissajous-Bowditch plots of normalized stress versus normalized strain offered new intracycle rheology insights.
- The nonlinear rheology of all four food materials showed very distinct structure rheology relationships.

The rheological properties of food products are important to design, improve and optimize the quality and sensory properties of food products as well as their processability. Rheological behavior is dependent on the type and concentration of constituents in a formulation. When foods products undergo different kinds of processing, they are often subjected to large deformations. The behavior of food products in large amplitude oscillatory flow (LAOS) can offer better understanding of structural changes during processing and consumption. In this study, the nonlinear behavior of tomato paste, mayonnaise, soft and hard dough was investigated by utilizing the Ewoldt-McKinley Large Amplitude Oscillatory Shear Flow (LAOS) theory. LAOS parameters (GM′, GL′, ηM′, ηL′, e3/e1, v3/v1, S and T) were used to understand the structural changes in these food products at frequencies ranging from 0.5 to 15 rad/s and strain in the ranges of 0.01-200. Tomato paste and mayonnaise showed an irreversible structural change/decay in LAOS evidenced by strain softening (negative values in e3/e1) and shear thickening (positive values in v3/v1) in the mid oscillatory region followed by strain hardening (positive values in e3/e1) and shear thinning (negative values in v3/v1) in the large oscillatory region. In contrast strain hardening and shear thinning were observed (evidenced by positive values of e3/e1 and negatives values of v3/v1) for both soft and hard dough. LAOS measurements were able to clearly discriminate between the large amplitude behavior of tomato paste and mayonnaise, two concentrated dispersions in contrast to soft and hard wheat flour dough two materials whose rheological behavior is highly affected by the protein network surrounding the dispersed starch phase.