Gelatinization temperature

Com and rice starches have been oxidized and subsequently cyanoethylated (97). As molecular size decreases due to degradation during oxidation, the degree of cyanoethylation increases. The derivatized starch shows pseudoplastic flow in water dispersion at higher levels of cyanoethylation the flow is thixotropic. Com and rice starches have been oxidized and subsequently carboxymethylated (98). Such derivatives are superior in the production of textile sizes. Potato starch has been oxidized with neutral aqueous bromine and fully chemically (99) and physically (100) characterized. Amylose is more sensitive to bromine oxidation than amylopectin and oxidation causes a decrease in both gelatinization temperature range and gelatinization enthalpy. 

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. 

Cationic starches show decreased gelatinization temperature range and increased hot paste viscosity. Pastes remain clear and fluid even at room temperatures and show no tendency to retrograde. This stabiUty is due to Coulombic repulsion between positively charged starch molecules in dispersion. 

Compared to native starches, monophosphate esters have a decreased gelatinization temperature range and swell in cold water at a DS of 0.07. Starch phosphates have increased paste viscosity and clarity and decreased retrogradation. Their properties are in many ways similar to those of potato starch, which naturally contains phosphate groups. 

Low DS starch acetates have reduced gelatinization temperature ranges and reduced tendency to retrograde after pasting and cooling. Gelling may be completely inhibited if the DS is sufficiently high. Low DS starch acetate polymers also form films which are useful in textile and paper manufacture. 

The sweetness of fmctose is enhanced by synergistic combiaations with sucrose (12) and high iatensity sweeteners (13), eg, aspartame, sacchatin, acesulfame K, and sucralose. Information on food appHcation is available (14,15). Fmctose also reduces the starch gelatinization temperature relative to sucrose ia baking appHcations (16—18). 

Gelatinization is accompanied by a loss of birefringence. The temperature at which this occurs is called the gelatinization temperature. 

In general, derivatization increases solution and gel clarity, reduces the tendency to gel, improves water binding, increases freeze—thaw stabiHty, reduces the gelatinization temperature, increases peak viscosity, and reduces the tendency to retrograde. Combinations of substitutions are used to obtain desiredproperti.es for specific appHcations. 

Paeschke, T.M. 2002. The Effect of Starch Microstructure on the Glass Transition, Gelatinization, and the Elevation of the Gelatinization Temperature by Saccharides . Ph.D. Thesis, University of Illinois at Urbana-Champaign. 

Pea starch granules are oval, sometimes fissured, with a diameter of 20-40 ym (13). Molecular and structural characteristics of the two main components of field pea starch—amylose and amylopectin—are important in determining functional properties (25,26). Smooth field pea starch concentrate contains 97.2% starch of which 30.3-37.8% is amylose (9,23,25-27), and wrinkled pea starch concentrate contains 94.8% starch, which is 64% amylose (26). The gelatinization temperature of smooth pea starch is between 64 to 69 C, and that of wrinkled pea starch is greater than 99 C to 115 C. Gelatinization temperature depends on maturity of field pea seed and amylose content (26,27). 

Some of these low-temperature treatments meet the hydro-thermal conditions of classic starch annealing procedures. Annealing is normally conducted below gelatinization temperatures in the presence of excess water (Jacobs and Delcour, 1998 Tester and Debon, 2000 Ozcan and Jackson, 2003). 

The term "annealing" is not completely applicable to all the treatments they used because some of the holding temperatures are above the gelatinization temperature of rice starch. 

Evans, I. D. and Haisman, D. R. (1982). The effect of solutes on the gelatinization temperature range of potato starch. Starch/Stdrke 34, 224 231. 

Gough, B. M. and Pybus, J. N. (1971). Effect on gelatinization temperature of wheat starch granules of prolonged treatment with water at 50 °C. Starch/Starke 23, 210-212. 

Shiotsubo, T. (1984). Gelatinization temperature of potato starch at the equilibrium state. Agric. Biol. Chem. 48, 1-7. 

Table 9.6 Gelatinization temperatures of starch from RB and YG potato samples heated in water...

Esterification Lower gelatinization temperature Used in refrigerated and frozen... 

Determine the gelatinization temperature of the starch in the cell wall residue by resuspending starch in 10 ml of 20 mM HEPES buffer, pH 6.9 containing 2 mM CaCl2... 

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