Rice starch, dextrinization

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. 

Fig. 37.—G, corn starch H, rice starch I, corn dextrin J, pea starch K, cassava starch L, bean starch. Explanation in text.

This results from the transformation of starch by means of heat or by the action of dilute acid or diastase. It is prepared principally from potato, wheat or maize starch and rarely from rice or other exotic starches. Many varieties of dextrin, made in diverse ways, are sold under different names. It occurs as a fine powder, either wliite, dirty white, yellowish or light brown as granules, similar in appearance to gum arabic and as a thick syrup, more or less highly coloured and opaque. In general dextrin has a special odour and taste, which are particularly marked in the pulverulent varieties. It is soluble in water, but insoluble in alcohol. Its solution is strongly dextro-rotatory the value of [a]D varies from 173° to 2250,but is mostly about 200°. With iodine different dextrins give bluish violet to brownish red colorations (the colour is observed by adding the iodine solution drop by drop if the mass is mixed after the first drops are added, the colour disappears). 

Pure chocolate is a mixture of torrefied, powdered cacao with sugar (saccharose) sometimes excess of fat is added and sometimes a small quantity of various essences or spices. Starch chocolate contains, in addition, one of a number of starches or flours (of rice, oats, chestnut, or of oily seeds such as walnut, arachis, etc.). Chocolate of lower quality sometimes contains powder cacao husks, and occasionally other sugars than saccharose (glucose) are added other adulterants are dextrin, gum and gelatine. Milk chocolate is prepared with cacao, sugar and milk powder or extract. 

Aspergillus oryzee is a yellowish-green to brown mold which secretes diastase, a valuable digestive ferment, having the power of converting starch into sugar and dextrin. For centuries the Japanese have employed this species in the preparation of rice mash for... 

Amylase enzymes also work on food stains containing starches, such as rice, spaghetti sauce, potatoes, oatmeal, and gravy. These enzymes hydrolyze the 1-4 glucosidic bonds in starch, which leads to the formation of smaller water-soluble molecules. a-Amylase randomly hydrolyzes the bonds in the starch polymer to form dextrin molecules. p-Amylase, in contrast, cleaves the maltose units that are situated at the end of the starch polymer. 

Starch occurs as microscopic granules in the roots, seeds and tubes of plants. Corn, potatoes, rice and wheat are important commercial sources. Over 5 billion pounds of starch are manufactured in the U.S. each year. About half of the starch is sold as starch and dextrin and about 1.5 billion pounds are converted into starch syrup. Most of the starch is employed to size and stiffen weaving yarn and to finish cloth. Starches are also used in making plywood, wallboard, posterboard and corrugated board. 

Starch is a natural product from renewable resources, produced during photosynthesis as food reserve for plants and vegetables. It is the second most abundant biomass material in nature. It is found in plant roots, stalks, and crop seeds. The most important industrial starch sources are crops such as corn, wheat, potato, tapioca and rice. By refining these crops several byproducts can be obtained such as oil, bran, gluten, dextrin, sugar (glucose, fructose, HFCS), ethanol (for beverages and bio-fuels) and starch. 

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