Rice starch

In industrial production of acid-modified starches, a 40% slurry of normal com starch or waxy maize starch is acidified with hydrochloric or sulfuric acid at 25—55°C. Reaction time is controlled by measuring loss of viscosity and may vary from 6 to 24 hs. For product reproducibiUty, it is necessary to strictly control the type of starch, its concentration, the type of acid and its concentration, the temperature, and time of reaction. Viscosity is plotted versus time, and when the desired amount of thinning is attained the mixture is neutralized with soda ash or dilute sodium hydroxide. The acid-modified starch is then filtered and dried. If the starch is washed with a nonaqueous solvent (89), gelling time is reduced, but such drying is seldom used. Acid treatment may be used in conjunction with preparation of starch ethers (90), cationic starches, or cross-linked starches. Acid treatment of 34 different rice starches has been reported (91), as well as acidic hydrolysis of wheat and com starches followed by hydroxypropylation for the purpose of preparing thin-hoiling and nongelling adhesives (92). 

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. 

Sodium chlorite oxidation of com and rice starches is recommended for the production of textile sizes (101) and oxidized starch is recommended as a hardening agent in the immobilization of microbial cells within gelatin (102). 

Seven diets were constructed from purified natural ingredients obtained from either C3 (beet sugar, rice starch, cottonseed oil, wood cellulose, Australian Cohuna brand casein, soy protein or wheat gluten for protein) or C4 foodwebs (cane sugar, corn starch, com oil, processed corn bran for fiber, Kenya casein for protein) supplemented with appropriate amounts of vitamins and minerals (Ambrose and Norr 1993 Table 3a). The amino acid compositions of wheat gluten and soy protein differ significantly from that of casein (Ambrose and Norr 1993). 

Conventional improvers are not used in rye bread but additives are sometimes used to increase the water absorption of the dough. Examples are polysaccharide gums such as guar and locust bean gum as well as pregelatinised potato flour, rice starch or maize starch. 

The favoured solution seems to be xanthan gum with rice starch and potato starch. Other systems use sorghum flour. 

The xanthan gum, rice starch and potato starch system is available as a mix to be made in domestic bread makers. 

FIGURE 5.11 DSC endotherms of rice starch annealed at 70 °C (times are indicated next to each profile) [adapted from Nakazawa et al. (1984) reproduced with permission from Japan Science and Technology Agency]. 

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. 

Biliaderis, C. G., Page, C. M., Maurice, T. J., and Juliano, B. O. (1986). Thermal characterization of rice starches A polymeric approach to phase transition of granular starch. /. Agric. Food Chem. 34, 6-14. 

Chung, H.-J., Lee, E.-J., and Lim, S.-T. (2002). Comparison in glass transition and enthalpy relaxation between native and gelatinized rice starches. Carbohydr. Polym. 48, 287-298. 

Gelatinization of sweet potato, tania, and yam tuber starches. Starch/Starke. 47, 298-306. Varavinit, S., Shobsngob, S., Varanyanond, W., Chinachoti, P., and Naivikul, O. (2003). Effect of amylose content on gelatinization, retrogradation and pasting properties of flours from different cultivars of Thai rice. Starch/Starke 55,410-415. 

The production of ethanol from cooked rice starch (Moebus and Teuber, 1985) differs from the normal process of spraying the carbon source into the bed since all of the carbon source is made available at the start of the run, subject only to the breakdown of starch to glucose (and maltose) by amylases. The starch (0.3 mm particles), amylases and yeast pellets were mixed in the bed and water sprayed in to maintain the fermentative activity of the yeast. The fermentation was carried out at 31.5°C. 

MEASUREMENTS OF THE CRUSHING STRENGTH OF A TABLET FORMULATION, jc, = a-LACTOSE 2= p-LACTOSE Xj = RICE STARCH Y-MEAN = AVERAGE OF TEN MEASUREMENTS OF THE CRUSHING STRENGTH (N)... 

Components with a fixed concentration were Primojel (4%), oxazepam (4%), magnesium stearate (1%) and Aerosil 200R (0.2%). The components with a variable concentration were a-lactose, 6-lactose and rice starch. The concentrations of these components sum up to 90,8% of the total tablet weight, their individual concentrations can be obtained from the experimental design listed in Table 4.3 where the listed values of Xj-Xj are fractions of the total amount of 90.8% for these three components. 

PARETO-OPTIMAL POINTS. Xi=a-LACTOSE X2=P-LACTOSE X3=RICE STARCH y,= PREDICTED VALUE OF THE CRUSHING STRENGTH (N) y2=C OF THE CRUSHING STRENGTH... 

The Storage to Initial Ratio of two tablet parameters crushing strength (S) and disintegration time (D) were measured for a combination of one filler-binder (a-lactose monohydrate) and one disintegrant (rice starch), at three concentration levels. 

The used tablet ingredients were a-lactose monohydrate (Ph.Eur grade, 100 mesh), rice starch (Ph.Eur. grade) and magnesium stearate (Ph.Eur. grade). Before use the magnesium stearate was sieved through a 210 im sieve. Prior to use, the materials were stored at 20 1 °C and 45 5% relative humidity (RH) for at least one week. 

For the disintegration time two models were calculated, which describe the effect of the four variables on the disintegration time and the SIR of disintegration time after storage of lactose/rice starch tablets ... 

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