Rice Starch, 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. 

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. 

The iodine affinities, blue values, max, beta-amylolysis limits and branch chain length distributions are similar for the starch samples harvested at different stages (7 to 30 days DAF) of development of waxy rice grains,331 japonica rice328 and indica rice.332 The gelatinization temperature of maize starch increases from 12 to 24 DAF, but is reduced at 36 DAF.333... 

Properties of rice starches are changed by chemical modification in the same way as the properties of other starches (see Chapter 18). Starches prepared via the alkali method have been modified to provide additional pH and shear stability. In general, hypochlorite-oxidized rice starch has a lower gelatinization temperature and lower maximum paste viscosity producing a softer, clearer gel. Hydroxypropylated rice starches have lower gelatinization temperatures, whereas crosslinked rice starch has an increased gelatinization temperature, increased shear resistance and acid stability. 

Also referred to as sweet or glutinous, waxy rices are characterized by opaque endosperms in which the starch is practically 100% amylopectin. Most varieties are classified as short and have a low gelatinization temperature, and relatively low amylograph peak, hot paste, and cool paste viscosities. When cooked they tend to lose their shape and are sticky or glutinous. Waxy rices are used to prepare sushi. 

Tempered or nonconditioned maize grits, rice grits, and starches are introduced and transported into the barrel section of the stator, and the shear applied by the screw movement increases both the pressure and internal temperature (more than 120°C) so that the starch gelatinizes, melts, and plasticizes. The rotor fingers cut the extruding material, which is then immediately extruded radially between the two... 

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