Starch preparation

Modified starches may be acid-modified, oxidized, or heat-treated. Acid-modified (thin-boiling) starches are used mainly in textiles as warp sizes and fabric finishes. Here they increase yam strength and abrasion resistance and improve weaving efficiency. Tbin-boiHng starches also have selected appHcations in paper and laundry starch preparations. 

Grain legumes have also been processed into refined starch (10,11) and protein isolates (12,13,14) by procedures derived from the traditional corn starch and soybean protein industries (15). However, comparative data on product yields, composition and losses have not been published. A commercial plant for the wet processing of field pea into refined starch, protein isolate and refined fiber has been established in Western Canada. Little is known about the characteristics of the protein isolate or refined fiber product. Water-washed starch prepared from the air-classified starch fractions of field pea (16,17) and fababean (6) have been investigated for certain physico-chemical and pasting properties. Reichert (18) isolated the cell wall material from soaked field pea cotyledons and determined its fiber composition and water absorption capacity. In addition, the effects of drying techniques on the characteristics of pea protein Isolates have been determined (14). 

Starch is isolated from plant sources by various methods (Ratnayake and Jackson, 2003 Zobel, 1992). The method of starch isolation depends on the nature and composition of the raw material source. Most food starches are isolated and purified on a commercial scale and then used as ingredients by food manufacturers. Commercial food starches are generally classified based on both botanical origin and functionality. With the increasing availability of modified starches prepared for specific food applications, starch manufacturers tend to emphasize and market starch with a secondary focus on botanical source. In fact, for food... 

Rajagopalan, S., Seib, P. A. (1992). Properties of granular cold-water soluble starches prepared at atmospheric pressure. J. Cereal Set, 16,29 0. 

Sodhi, N. S., Singh, N. (2005). Characteristics of acetylated starches prepared using starches separated from different riee eultivars. J. Food Engg., 70,117-127. 

Woo, K. S. (1999). Cross-linked, RS4 type resistant starch preparation and properties. PhD Thesis. Kansas State University Manhattan, KS. 

These difficulties are avoided by using a pure soluble starch preparation and by... 

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... 

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. 

Water-binding capacity (WBC) was reported to be 141% for starch prepared from mature rye,7 whereas it was somewhat higher for starch prepared from immature rye. 

A WBC value of 86.5% has also been reported.10 Examples of the swelling power and solubility are given in Table 14.2. These values were obtained for starch from mature rye values for starch prepared from immature rye were higher. Values for rye starch were lower than those for wheat starch.7 In a study of nine different rye starches, the gel volume at 90°C was determined to be in the range 14.8-19.7mL/g, and the leached amylose to be 120-172 mg/g starch.8... 

The corn syrup industry is a good example of how enzymes took over and improved an industry after it was established as a profitable and important industry. In the beginning, acid was used as the catalyst to hydrolyze starch into syrups in order to impart new and desirable attributes to food products. The process involved treating a 40%-45% solution of refined starch with hydrochloric acid at pH 1.5 and a temperature of 150°C for a few minutes. The acid was not selective and hydrolyzed the protein and fat present in the starch preparation as well as the starch. This led to extensive undesired browning due to Maillard reactions. The syrup was neutralized, filtered, carbon-treated, and ion-exchange treated to become a food product or an ingredient to be used by other food processors in preparing products. 

Manganese Determine the residual manganese in bleached starch prepared with potassium permanganate as directed under Manganese, Appendix IIIB. 

Note The treatment outlined above is satisfactory for starch products that are insoluble in cold water. For pregelatinized starch and other water-soluble starches, prepare a 1% to 2% aqueous paste, place it in a cellophane tube, and dialyze against running distilled water for 30 h to 40 h. Precipitate the starch by pouring the solution into 4 volumes of acetone per volume of paste while stirring. Recover the starch by vacuum filtration in a medium-porosity fritted-glass or Buchner funnel, and wash the filter cake with absolute ethanol. Dry the filter cake, and determine the amount of dry substance as directed for water-insoluble starches. 

While whole starch is very slowly or incompletely dissolved by mixtures of acetic acid, acetic anhydride, and sulfuric acid, the acetyl content of the dissolved portion rises rapidly with increased amounts of sulfuric acid or the application of higher temperatures." In contrast to whole starch a finely divided, fluffy starch, prepared as described in Section II, might be expected to be acetylated rapidly and completely by mixtures of acetic acid, acetic anhydride, and sulfuric acid. 

Wheat Starch Preparation. Edible wheat starch (Hercules No. 120) obtained through the Northern Utilization Research and Development Division, U. S. Department of Agriculture, Peoria, 111., was used throughout these experiments. The dry starch was prepared by dispersing it in benzene, distilling off the azeotrope, and drying in a vacuum oven at 100° C. 

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