Starch paste

Thixotropy and Other Time Effects. In addition to the nonideal behavior described, many fluids exhibit time-dependent effects. Some fluids increase in viscosity (rheopexy) or decrease in viscosity (thixotropy) with time when sheared at a constant shear rate. These effects can occur in fluids with or without yield values. Rheopexy is a rare phenomenon, but thixotropic fluids are common. Examples of thixotropic materials are starch pastes, gelatin, mayoimaise, drilling muds, and latex paints. The thixotropic effect is shown in Figure 5, where the curves are for a specimen exposed first to increasing and then to decreasing shear rates. Because of the decrease in viscosity with time as weU as shear rate, the up-and-down flow curves do not superimpose. Instead, they form a hysteresis loop, often called a thixotropic loop. Because flow curves for thixotropic or rheopectic Hquids depend on the shear history of the sample, different curves for the same material can be obtained, depending on the experimental procedure. 

Specific optical rotation values, [a], for starch pastes range from 180 to 220° (5), but for pure amylose and amylopectin fractions [a] is 200°. The stmcture of amylose has been estabUshed by use of x-ray diffraction and infrared spectroscopy (23). The latter analysis shows that the proposed stmcture (23) is consistent with the proposed ground-state conformation of the monomer D-glucopyranosyl units. Intramolecular bonding in amylose has also been investigated with nuclear magnetic resonance (nmr) spectroscopy (24). 

Hydroxyethyl group introduction at low DS results in distinct modification of physical properties. Among these are decreased gelatinization temperature range (126), increased granule swelling rate (127), and decreased abiUty of starch pastes to gel and retrograde. 

The assay determination of sulfamic acid is made by titration of an accurately prepared sulfamic acid solution using sodium nitrite solution and an external potassium iodide starch-paste indicator. It is based on the reaction... 

Standard 1/10 N nitrite is used to titrate a solution prepared by dissolving 10—100 mg of sulfamic acid and about 6 mL of (1 + 1) H2SO4 in 300 mL of distilled water at 40—50°C. At the end point, the colorless external potassium iodide starch-paste indicator changes to blue. A 1-mL solution of 1/ION NaN02 is equivalent to 9.709 mg of sulfamic acid. The 1/10 N nitrite titrant solution is standardized using primary standard-grade sulfamic acid. For sulfamate assay determination, the same procedure is used as for sulfamic acid. 

Stftrke-kleister, m. starch paste, -kom, -korn chen, n. starch granule, -losung, /. starch solution, -mehl, n, starch flom. starch powder, starch. 

Starke-mehlkleister, m. starch paste, -messer, m. amylometer. -messung, /. measiirement of strength or size, -milch, /. thin starch paste, -mittel, n. strengthening remedy, tonic, restorative. 

DSC revealed that the XG and starch did not interact synergistically and hence did not promote the formation of three-dimensional network structures. However, the hydrocolloid significantly decreased the retrogradation and syneresis of the starch paste, particularly in blends with a starch/XG ratio of 8.5/1.5. Mixing 1% or 2% tamarind XG with 9% cornstarch resulted in an increase in the paste viscosity from 385 to 460 and 560 BU (Brabender units), respectively [298]. The XG is associated with starch, as was evident from the lowering of the pasting temperature and the synergistic increase in pseudoplasticity and yield value of the blend pastes. However, carboxymethylated and hydroxypropylated XGs showed a diminished interaction. 

By shaking a solution of ammonia and ammonium pyruvate with colloidal palladium in the presence of hydrogen, employing starch paste to stabilize the colloid. Aubel and Bourguel, Compt. rend. 186, 1844 (1928). 

Singh, V., Haken, A.E., Dowd, M.K., Niu, Y.X., Zou, S.H., and Eckhoff, S.R. 1999a. Batch steeping of com Effects of adding lactic acid and sulfur dioxide at different times on starch yields, protein contents, and starch pasting properties. Cereal Chem. 76, 600-605. 

Each of these amylases causes a rapid decrease in the viscosity of starch pastes and the rapid disappearance from its reaction mixtures of products that give color with iodine. During the early stages of the hydrolysis of starch, the relative decrease in the viscosity of the substrates for hydrolysates of equivalent reducing value is most marked... 

Zobel, H. F. (1984). Gelatinization of starch and mechanical properties of starch pastes. In "Starch Chemistry and Technology" (R. L. Whistler, J. N. BeMiller, and E. Paschall, eds.), pp. 285-309. Academic Press, Orlando, FL. 

In this study, we present evidence for the first time of a three-way interaction among starch, protein, and lipid that alters starch paste viscosity profiles. (Adapted from Zhang and Hamaker, 2003)... 

Blennow, A., Bay-Smidt, A. M., Leonhardt, R, Bandsholm, O., Madsen, H. M. (2003). Starch paste stickiness is a relevant native starch selection criterion for wet-end paper manufacturing. Starch, 55,381-389. 

Eliasson, A. C, Kim, H. R. (1992). Changes in rheological properties of hydroxypropyl potato starch pastes during freeze-thaw treatments I. A rheological approach for evaluation of freeze-thaw stability. J. Texture Stud, 23, 279-295. 

Wong, R. B. K., Lelievre, J. (1981). Viscoelastic behaviour of wheat-starch pastes. Rheol. Acta, 20,299-307. 

Mita, T. (1992). Structure of potato starch pastes on the ageing process by the measurement of their dynamic moduli. Carbohydrate Polymers, 12,269-276. 

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