Rheological assays

FIGURE 15.25 Pseudotemary diagram showing the gel region used in the formulation of fracturing fluids (temperature 26°C). The gel points shown correspond to the specific compositions tested in rheological assays. (From Dantas, T.N.C., Santanna, V.C., Dantas Neto, A.A., Barros Neto, E.L., and Moura, M.C.P.A., Coll. Surf. A, 225,129, 2003. With permission.)... 

The two methods described herein are inherently different in that one is a traditional initial velocity assay that attempts to quantitatively measure rates of product formation (see Basic Protocol 1), whereas the other correlates the activity of an enzyme preparation with its ability to change the rheological properties (i.e., viscosity) of a substrate solution (see Basic Protocol 2). For both assays, it is presumed that the analyst is using soluble substrate and enzyme preparations, appropriate buffer systems, and a method to control the reaction mixture temperature. The ultimate goal of both assays is the same to obtain a quantitative estimate of the PGase activity of a test solution. 

Discrepancies between the above studies vis-a-vis the effects of homogenization on the textural and rheological characteristics of cheese may be due to differences in homogenization conditions, assay conditions, age of cheese, and fat content. 

Size and shape factors in combination with fractal dimension and rheological tests provide, prior to preformulation assays, a reliable technique for the appropriate selection of materials and detection of undesirable properties related to shape-surface characteristics. 

Molecular mucin-based assays Viscometry and rheology Dynamic light scattering Turbidity, light scattering... 

In addition, for suspensions, redispersibility, rheological properties, and mean size and distribution of particles should be considered. After storage, samples of suspensions should be prepared for assay according to the recommended labeling (e.g., shake well before using ). 

The most important wheat flour functionality tests are the ones that determine dough rheological properties. These assays study the rheological properties of optimally hydrated and mixed dough. They are of utmost importance because these properties are strongly associated with processing (optimum water absorption and mixing time) and quality of bakery products. 

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