Thixotropy in food systems: A study on mayonnaise

Abstract

Understanding the rheological response and different phenomena exhibited by food products is useful in their processing, consumption and for developing alternative formulations. In this context, choice of a protocol is of importance in examining particular phenomenon. Thixotropy, a time-dependent phenomenon, observed in various food systems is often quantified through the hysteresis loop and 3iTT (three interval thixotropy test) tests. The observations from these tests offer limited insights. Therefore, in recent years, step shear tests have been proposed for studying thixotropy. In this work, we consider mayonnaise, which is well known for exhibiting thixotropy as a model material system. The rheological response of mayonnaise is measured through hysteresis loop, 3iTT, and step shear tests and compared with two mathematical models (TEVP (thixotropic elasto-viscoplastic) and EVP (elasto-viscoplastic)). An important observation is that, while the hysteresis loop test exhibits a small loop area and the 3iTT test response shows recovery of storage modulus ($G^{\prime }$) within 30 s, step shear tests quantify the breakdown and rebuilding times. There are also no significant quantitative differences between the models for hysteresis and 3iTT responses, however, differences exist in case of step shear tests. The TEVP model quantifies the material response well, while the EVP model exhibits a monotonic stress evolution. Therefore, step shear tests are a better alternative to hysteresis loop and 3iTT tests for studying thixotropy in food systems.