CHARACTERIZATION OF STRUCTURE BREAKDOWN OF FOODS FROM THEIR FLOW PROPERTIES (original) (raw)

1981, Journal of Texture Studies

Advances in the characterization of the complex time-dependent flow properties of liquids and semisolids are reviewed, with special emphasis placed on recent developments in elucidating the behavior of food systems when sheared. Time dependency is discussed in terms of viscoelasticity and structural changes. Systems as diverse as mineral oils, lotions and creams, egg custards, and mayonnaise are shown to exhibit a similar stress decay over time when sheared at a constant rate. Various mathematical descriptions, both theoretical and empirical, are used to characterize the stress decay, which is due to structural changes (e.g. thixotropy) that occur within the system as it is sheared. Evidence is provided that the stress decay varies with product fiwmulation and experimental conditions, such as temperature, shear rate, and viscometer gap width. A discussion of the uses and disadvantages of steady shear measurements is included. evaluation. Texture profiling, a powerful tool in the latter endeavor, has generally involved compression of a food product and subsequent analysis of the recorded force-time curve in terms of relevant bulk textural properties. Although other types of testing have been used in profiling, including flexure, puncture, extrusion and tension , steady shearing of food products has received relatively little attention. Shear stress-time curves recorded at constant shear rate, however, can provide a means of evaluating the textural properties of fluid and semisolid foods, as well as a means of studying their flow properties for process and product development.