Characterization of Structure Breakdown of Foods From Their Flow Properties

Abstract

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 formulation 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.

Effect of egg storage duration on the rheology of liquid egg products

“…Week r 0 (Pa) K (Pa s n ) n (1) In the next step liquid egg products were sheared at constant shear rate (54.5 s À1 ) for about 4000 s and changes of apparent viscosity with time was considered as time dependency (Figoni and Shoemaker, 1981).…”

Rheological Properties of Liquid Egg Products (LEPS)

“…Liquid egg products were sheared at constant low shear rates (LEW and LWE sheared at 16.12s −1 , LEY sheared at 8.48 s −1 ) for 420 s and changes of apparent viscosity with time was considered as time dependency. [23] …”

“…As the sample is sheared during its passage through the process system, the linkages between particles or molecules in the food are broken (structure breakdown), resulting in reduction in the size of the structural units and offer lower resistance to flow. [23] Thixotropic behavior of LEPs was examined by measuring hysteresis loop at different temperatures (Figures 2, 3, 4). It is evident from Figure 3 that none of the products exhibited thixotropy at 25°C.…”

Physicochemical Properties of Soybean Proteins Related to Flow, Viscoelastic, Mechanical and Water‐holding Characteristics of Gels

“…The time (t) dependency of viscosity (71) was expressed by the Urnstatter equation (Figoni and Shoemaker, 1981):…”

“…Contrary to Catsimpoolas and Meyer (1970), when the T-spindle rotated at the same position, the torque could not be recorded: thus measurements were made with the helipath stand by using a 2 cm pathway. The time (t) dependency of viscosity (71) was expressed by the Urnstatter equation (Figoni and Shoemaker, 1981):…”