Potato starch oxidized

For potato starch oxidized with 5 % sodium metaperiodate for twenty-four hours at room temperature, two of the three monosaccharide residues are transformed to formazans. 

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. 

Not all modified starches are suitable for removal by aqueous dissolution alone. Such modifications of natural starches are carried out to reduce solution viscosity, to improve adhesion and ostensibly to enhance aqueous solubility. Commercial brands vary [169], however, from readily soluble types to those of limited solubility. Indeed, some may be as difficult to dissolve as potato starch if they have been overdried. It is thus very important to be sure of the properties of any modified starch present. If there are any doubts about aqueous dissolution, desizing should be carried out by enzymatic or oxidative treatment. Even if the size polymer is sufficiently soluble, it is important to ensure that the washing-off range is adequate. Whilst the above comments relate to modified starches, other size polymers such as poly(vinyl acetate/alcohol) and acrylic acid copolymers vary from brand to brand with regard to ease of dissolution. 

The oxidation of starch in aqueous suspension with H202 in the presence of iron phthalocyanine gives both carboxylic and carbonyl groups (Table 3.1). The best yields were obtained with a molar ratio 12900/1 (0.0078 mol%), but the oxidation was still quite efficient with 0.0039 mol% of catalyst [25800 per anhydroglucose unit (AGU)/catalyst ratio]. The oxidized starch had almost the same final Fe-content as the initial potato starch. Still, the efficiency of this method in view of scaling up was limited by comparatively low activity and product isolation problems. 

Figure 10.6 Effects of hydroxypropylation on the granule morphology of potato starches, (a) Potato starch granules after hydroxypropylation (at 10% propylene oxide concentration), (b) Effect of increased concentration of propylene oxide (15%) on the starch granule structure (source Kaur et al., 2004).

Oxidation of Starch.97- 98- 114 Oxidation in Aqueous -Suspension. Ten grams of cornstarch or potato starch, previously dried at 100° for about twenty hours, is suspended in 290 cc. of 0.533 M aqueous periodic acid solution. After being shaken thoroughly, the mixture is kept at 20-25° for twenty-four hours. About one mole of periodic acid per C H oOs unit of starch reacts to yield oxidized starch (LYI). The product is filtered, washed free from iodic acid and excess periodic acid with cold water, and dried at 40-50°. The yield is quantitative. Over 99% of the substance dissolves in forty parts of water at 100° during two hours [a]o = +9°. 

Starch pastes irradiated with 130,000 V, 15 mA X-rays lost their viscosity, and there was concurrent decrease of iodine-binding ability and pH. Other properties measured after such treatment point to dextrinization and oxidation of starch.78-79 Other results of such irradiation is the cleavage of phosphoric acid esters from glucose units of potato starch. This effect is observed at 50,000 V and 8 mA as well as at 150,000 V and 12 mA. The effect of X-ray irradiation is similar in this respect to irradiation with 7-rays, whereas neither sonication with ultrasound nor exposure to UV light evoke such effects.5 Starch irradiated by X-rays, contains free radicals, and thus the presence of free radicals in starch provides evidence of previous irradiation. 

Starch—different kinds (potato, corn, and wheat starches) and many kinds of chemically modified starches (oxidized starches, phosphated distarch phosphate, etc.)... 

Anionic starches are obtained by reaction with phosphoric acid and alkali metal phosphates or by derivatization with carboxymethyl groups.30,31 This modification is primarily used to introduce amphoteric properties into cationic com starch for application on the wet end of the paper machine. Anionic starches with carboxymethyl substitution are used as thickeners in coating colors or as binders in coatings for specialty paper grades. Oxidized starches are inherently anionic but without thickening action. Potato starch already carries sufficient natural anionic charge to provide amphoteric properties after cationization.32... 

Starch for use in papermaking has to meet specific purity requirements in residual oil, protein, bran and ash content. Industrial starches have a protein content (N X 6.25), ranging from about 0.05% for potato starch to 0.3-0.6% for com starch, depending on separation efficiency during production. Excess protein content will induce foaming in dispersions of starch and affect the quality and strength of the coated surface. Starch for use in the paper industry should not contain more than 0.4% protein. Oxidized starches tend to have the lowest protein content. Residual oil will cause retrogradation due to complex formation with amylose. 

Sealing tape has 35 to 90 pounds per ream of kraft paper as a substrate, whereas, reinforced sealing tape is based on a bonded laminate of kraft paper, reinforcing fibers, and kraft paper. The adhesives applied to these substrates may be thin-boiling, waxy starches alone, or blended with a soluble dextrin (5). More recently, blends of a soluble dextrin with oxidized potato or a hydrox-ypropyl ether of an oxidized potato starch are being used (9). Also, the acetate or succinate of an oxidized waxy starch may be used (15) as well as specially produced waxy starch acrylamide graft copolymer products (16). 

In order to study the influence of magnesium sulfate at temperatures well above 100°, experiments were done in another way. Potato starch was suspended in an aqueous, magnesium sulfate solution of the desired concentration. Sufficient magnesium oxide was added to ensure that the pH of the system at the end of the fractionation process would be within the... 

Slow but significant progress is visible in this area. For example, potato starch (containing 27 % amylase and 73 % amylopectin) can be oxidized to superabsorbing biopolymers. The three-component system H202/HBr/CH3Re03 works in the formation of carboxylated starch according to the mechanism proposed in Scheme 10 [104],... 

Bryce and Greenwood studied the kinetics of formation of the major volatile fraction from potato starch, and its components. They limited their interest to the temperature range from 156 to 337 and to the formation of water, as well as of carbon mon- and di-oxide. The results revealed the following facts. Stability toward pyrolysis within the first 20 minutes of the process falls in the order amylose < starch < amylopectin < cellulose. Autocatalysis is absent, as shown by Puddington. Both carbon mon- and di-oxide are evolved as a consequence of each of two first-order reactions. The initial one is fast, and the second is slow. The reasons are not well understood, but they probably involve some secondary physical effects. The amount of both carbon oxides is a direct function of the quantity of water produced from any polysaccharide, which, furthermore, is independent of the temperature. The activation energy for the production of carbon mon-and di-oxide reaches 161.6 kJ/mol, and is practically independent of the polysaccharide formed. At the limiting rates, the approximate ratios of water carbon dioxide carbon monoxide were found to be 16 4 1 for amylopectin, 13 3 1 for starch, 10 3 1 for amylose, and 16 5 1 for cellulose. 

The first quantitative results for the decomposition of starch into carbon monoxide, carbon dioxide, and water are those of Puddington. He showed that pyrolysis of starch is more rapid under vacuum than at atmospheric pressure, that is, that the reaction probably does not involve oxidation. Puddington made a kinetic study of the decomposition of potato starch, in the narrow temperature range of 180-210°, at 10 mm. A conventional, vacuum line of glass permitted the pyrolysis products to be trapped or collected. The amounts of carbon monoxide, carbon dioxide, and water were determined by classical, gas-analysis techniques. 

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