Measurement of Flow Properties of Fluid Foods ‐ Developments, Limitations, and Interpretation of Phenomena

Abstract

Rheological behavior of fluid foods is described with examples under each type of behavior. Benefits of fundamental rheological data are illustrated for engineering studies, sensory evaluation, and detection of compositional changes. Some problems likely to be encountered due to sampling are discussed along with possible remedies. Theoretical bases for the proper use of capillary, concentric, and plate and cone visco‐ meters are outlined as well as the effects of violating the theoretical requirements. Xeld stress and rheological equations employed to describe foods possessing yield stress are reviewed. Use of mixers as viscometers for studying flow properties of foods is covered.

Capillary Extrusion Viscometer for the Viscosity Measurement of Fish Protein Paste

“…1963). Specific assumptions are typically given for the capillary viscometer such as steady flow, no end effects and no radial and tangential components of velocity in the capillary viscometer (Rao 1977). However, the flow behavior of non‐Newtonian surimi paste with or without salt could be well defined using the capillary viscometer.…”

FLOW BEHAVIOR of TOMATO SAUCE WITH OR WITHOUT PARTICULATES IN TUBE FLOW1

“…The particulates act as a suspension of solid particles and these tend to migrate away from the walls. This results in lower concentration and lower effective viscosity within the tube ("Pinch effect", Rao 1977). The results obtained are shown in Table 3.…”

“…Much literature is available on flow behavior measurements of foods using viscometers like the rotating cylinder (Brekke er al. 1978;Crandall et al 1982;Harper and Lebermann 1962;Harper and Sahrigi 1965;Berk 1970, 1972;Rao 1977;Rao et al 1974Rao et al , 1981, and cone and plate types (Davis 1973) and tube viscometers (Sarvacos 1968;Vitali and Rao 1982). However, most of these researchers have limited their study to product temperatures of 60°C or less.…”

ANALYSIS of the HELICAL SCREW RHEOMETER FOR FLUID FOOD

“…During food processing marked physical and chemical changes can occur, so it is desirable to monitor the process to achieve greater process and quality control (Rao 1977a). On-line rheological measurements in the food industry have been limited (Whorlow 1980;Van Wazer et al 1963;Tily 1983) and the available instruments do not measure fundamental physical parameters; they are primarily empirical in nature.…”

“…A single constant is not sufficient to characterize the shear stress versus shear rate behavior of a non-Newtonian fluid. A common non-Newtonian model used for this purpose is the power law model (Rao 1977b) defined as r = m;/"…”