Solubilities, starch polymers

Alpha-amylases are characterized by attacking the starch polymer in an endo fashion, randomly cleaving internal 1,4-bonds to yield shorter, water-soluble dextrins. They are the preferred type of amylase for laundry detergents, and are included in both powder and Hquid formulations in many countries. 

The synthetic approach is very simple and does not require any special set up. In a typical room temperature reaction, 1.0 mL aqueous solution of cadmium chloride was added to 20 mL aqueous solution of soluble starch in a 50 mL one-necked round-bottom flask with constant stirring at room temperature. The pH of the solution was adjusted from 6 to 11 using 0.1 M ammonia solution. This was followed by a slow addition of 1.0 mL colourless selenide ion stock solution. The mixture was further stirred for 2 h and aged for 18 h. The resultant solution was filtered and extracted with acetone to obtain a red precipitate of CdSe nanoaprticles. The precipitate was washed several times and dried at room temperature to give a material which readily dispersed in water. The same procedure was repeated for the synthesis of PVA and PVP - capped CdSe nanoparticles by replacing the starch solution with the PVA and PVP polymers while the synthesis of elongated nanoparticles was achieved by changing the Cd Se precursor ratio from 1 1 to 1 2. The synthesis of polymer capped ZnSe nanoparticles also follows the same procedure except that ZnCb solution was used instead of CdCb solution. 

The desizing of water-soluble size polymers can be summarised as follows. Batchwise or continuous methods can be used in both cases an adequate supply of hot water is needed during the washing-off. Hot water and detergent are needed to remove polyfvinyl alcohol) or carboxymethylcellulose. The addition of alkali may be beneficial with carboxymethylcellulose. Alkali is essential with modified starches and acrylic acid copolymers. Polyfvinyl alcohol) can be degraded effectively by alkaline oxidation. 

An interesting feature of current commercial products is that the polymer vehicles available for formulation have been limited to nonionic and anionic materials. The delivery vehicles available included off-the-shelf polymers such as carboxymethylcellulose, soluble starch, hydroxyethyl-cellulose, polyvinyl alcohol, poly(acrylic acid), and polyvinylpyrrolidone, or mixtures thereof. The choice of available polymeric delivery system primarily depends on component compatibility, aesthetics, and efficacy. However, by reliance upon available (off-the-shelf) systems, limitations on bioadhesion, drug bioavailability, contraceptive efficacy, and end-use characteristics has been limited. 

Starch is composed of macromolecular components, a-amylose and (i-aim -lose. The former reacts irreversibly with iodine to form a red adduct. (i-Aim losc. on the other hand, reacts with iodine forming a deep blue complex. Because this reaction is reversible, [3-amyl0sc is an excellent choice for the indicator. The undesired alpha fraction should be removed from the starch. The soluble starch that is commercially available, principally consists of (3-amylose. (3-Amylose is a polymer of thousands of glucose molecules. It has a helical structure into which iodine is incorporated as I5. ... 

Preparation of DMS0-Soluble Starch-g-PAN Samples and Water-Soluble Starch-g-Polyacrylamide. Five grams of starch- -PAN (prepared by either ceric- or cobalt-60 initiation) was dispersed in 333 g of DMSO, and the dispersion was heated for 2 hr at 115°C. The cooled dispersion was then treated with ultrasound for 10 min to mechanically rupture gel particles and to render the polymer soluble (Branson Sonifier, Model S 125 ... 

Five grams of starch-g-polyacrylamide was dispersed in 333 ml of water and the mixture was heated for 4.5 hr at 95-100°C. The cooled dispersion was then treated with ultrasound, as described for starch-g-PAN in DMSO. The resulting solution was gravity-filtered through fluted Whatman 54 paper, and the filtrate was freeze-dried to give 4.4 g of polymer. To give a denser, more compact product, which might more closely resemble soluble starch-g-PAN, the freeze-dried polymer was dispersed in 20 ml of water, and the polymer was precipitated from the thick paste by addition of ethanol. The polymer was separated by filtration, washed with ethanol, and vacuum dried at 60°C. 

Retrogradation is the reassociation of solubilized starch polymers in their native state or those in dextrins or in low-DE hydrolyzates resulting in an insoluble precipitate. Dextrins are depolymerized starches produced by heating a starch moistened with dilute hydrochloric acid or heating a moist starch in the presence of gaseous hydrogen chloride until a cold-water-soluble product is formed. 

Kato, Y., Matsuo, R., and Isogai, A., Oxidation process of water-soluble starch in TEMPO-mediated system. Carbohydrate Polymers 2003, 51 (1), 69-75. 

The most relevant achievements in this sector are related to thermoplastic starch polymers resulting from the processing of native starch by chemical, thermal and mechanical means, and to its complexation to other co-polymers. The resulting materials show properties ranging from the flexibility of polyethylene to the rigidity of polystyrene, and can be soluble or insoluble in water as well as insensitive to humidity. Such properties explain the leading position of starch-based materials in the biodegradable polymer field. 

Arvanitoyannis, I., and Biliaderis, C.G. (1999). Physical properties of polyol-plasticized edible blends made of methyl cellulose and soluble starch. Carbohydrate Polymers. 38(1), 47-58. 

Psomiadou, E., Arvanitoyannis, 1., Biliaderis, C.G., Ogawa, H., and Kawasaki, N. (1997). Biodegradable films made from low density polyethylene (LDPE), wheat starch and soluble starch for food packaging applications. Part 2. Carbohydrate Polymers. 33, 227-242. 

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. 

The shape of the gelatinization diagram of starch is very similar to the stability diagram for the denaturation of proteins as given in Fig. 2, and the cloud point of water soluble synthetic polymers [94]. This is quite remarkable given the major differences in composition between these polymers. 

A C. reinhardtii mutant lacking D-enzyme activity has been characterized and has been shown to have significantly lower levels of starch. Other enzymes involved in starch metabolism such as ADP-Glc PPase, granule-bound and soluble starch synthase, BE, phosphorylase, a-glucosidase, amylases, and debranching enzyme activities were not affected. The starch content in the mutant was about 6-13% of wild type and there was an excessive accumulation of maltooligosaccharides up to a polymer size of 16 glucose units. 

Water-Soluble Starches, Gums, Cellulose Derivatives, and Synthetic Polymers. Water-soluble plant starches and gums have historically been used as glues and should be reversible. Some of the modern water-soluble polymers (e.g., cellulose ethers and esters and soluble nylon) should also be reversible. 

In this regard, polyvinyl alcohol (PVA), a hydrolysis product of polyvinyl acetate, is well suited for blending with natural polymers since it is highly polar and water-soluble synthetic polymer which is also biodegra ble. PVA and starch films have been prepared for use as agricultural mulch films and as water-soluble laundry bags. Cast films made firom PVA and cellulose, prepared in N,N-dimethylacetamide-lithium chloride, exhibited good miscibility due to their mutual ability to form infra-... 

Starch is the primary source of carbohydrate in the human diet. Starch is composed of two monosaccharides amylose and amylopectin. Amylose is a linear polymer that varies in molecular weight between 100,000 and 500,000 g/mol. Amylopectin is similar to amylose, having the same backbone structure but with 4 percent branching. Starch is insoluble in water but can be made soluble by treating with dilute HCl. Soluble starch has similar properties to dextran and thoefore has similar applications. 

---