Rice starches preparation

Worldwide production of rice starch amounts to about 25 000 metric tons.20 Approximately 75% of this was manufactured by the Belgium company Remy Industries, which has been manufacturing rice starch by the traditional alkali method for more than 100 years. Until 1990, rice starch prepared by the alkali process was the only commercially-available rice starch. 

RVA curves compare commercial rice starch prepared by traditional alkali methods and rice starches prepared by the mechanical method. In the case of common rice starches, the onset of pasting appears to occur earlier (at lower temperature) and the final cooled viscosity appears to be lower for the starches prepared using alkaline conditions. The latter differences may be due to either rice type or the effect of alkali on granules. In the case of waxy rice starches, mechanically produced starches, in... 

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). 

Each combination behaves differently after storage. In all cases there was an effect of the starch concentration (y i sir(d) is significant). In most cases the relative humidity as well as the interaction between the relative humidity and the disintegrant concentration plays a role in the disintegration time of tablets prepared with either lactose. The dicalcium phosphate dihydrate/rice starch combination is influenced very strongly by the three factors studied. This combination is not suitable for use in tropical countries. Neither is the combination of B-lactose and crospovidone. 

Rice starch is preferably prepared from broken rice for economic reasons, as discussed above. There are currently two commercial methods of rice starch isolation traditional and mechanical. The traditional method involves alkali solubilization of rice protein, while the mechanical method releases starch via a wet-milling process. 

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. 

Cationic oat starch was used to improve the dry strength of paper handsheets and found to be comparable to wheat starch in functionality.14 Oat starch might possibly be a replacement for rice starch in pharmaceutical applications.19 Oat flour has been used in adhesive preparations.19... 

The cohesive power of glutinous rice starch is very strong this is seen clearly by comparing this starch with others like dextrine. Add ten times as much water to glutinous rice starch and stir well. Test it between the fingers, and it is clear how far more cohesive it is than a dextrine solution which is prepared in the same way. 

This cohesive nature of glutinous rice starch is quite important especially for preparing round stars, because the essential point of the process lies in that the composition must be pasted in a wet state on the core using as little paste as possible Accordingly a paste which has a strong cohesive power satisfies the requirement well. For this reason glutinous rice starch is quite superior for manufacturing round stars. 

Rice starch, because of the small size of its granules, is preferred for preparing cosmetic dusting-powders and in the binding of pharmaceutical tablets. Imports into the U. S. are principally from Belgium and Egypt. 

Peerapattana, J. Phuvarit, R Srijesdaruk, V. Preechagoon, D. Tattawasart, A. Pregelatinized glutinous rice starch as a sustained release agent for tablet preparations. Carbohydr. Polym. 2010, 80 (2), 453-459. 

Some substances are available in several degrees of fineness. The raw material triamcinolone acetonide is available as a micronised powder, to be used if triamcinolone acetonide is dispersed in a base. The micronisation may increase dissolution rate and hence bioavailability. It has, however, a strong agglomeration tendency and therefore cannot be processed as such. The 1 to 10 dispersion with rice starch contains micronised triamcinolone acetonide, whose particles don t agglomerate any more due to the presence of rice starch and it may be preferred for the preparation of creams. Triamcinolone acetonide (crystalline form) as such can be used if it is dissolved in propylene glycol (for ointments) or in ethanol (for ear drops). 

Triamcinolone acetonide in dermal preparations is processed as a trituration with rice starch (1 10). Here, the particles of triamcinolone acetonide are reduced in size firstly by dissolving the substance in a volatile solvent, after which this solution is rubbed until dry with rice starch. The resulting particles of triamcinolone acetonide of about 5 pm are in this way mixed with and held apart by the starch particles. By pulverising triamcinolone acetonide as such in a mortar such fineness of particles is not achieved. Moreover, agglomerates will be created. Also rubbing the solution until dry without rice starch does not yield a good result. Not only agglomerates will be recreated, but part of the triamcinolone acetonide will crystallise in a coarser form. 

Piyada et al. (2013) prepared a rice starch solution with a concentration of 3 % (w/v) in distilled water. They heated the dispersion with continuous stirring until it was completely gelatinized (85 °C for 5 min), and finally cooled it to 45 2 °C. Subsequently, previously lyophilized nanocrystals were dispersed in water, and incorporated to the gelatinized starch suspension. 

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