Starch, oxidation

Oxidized starches Oxidizers Oxidizing alkyds Oxidoreductases... 

Starch oxidation was investigated as early as 1829 by Liebig. The objective, as with other modifications, was to obtain a modified granular starch. The oxidant commonly employed is sodium hypochlorite, prepared from chlorine and aqueous sodium hydroxide. This reaction is exothermic and external cooling must be provided during preparation of the oxidant. 

Oxidation also results in starch depolymerization, which is the cause of the low viscosity and improved clarity and stability exhibited by oxidized starches. Oxidized starches are used in foods as coating and sealing agents in confectionary, as an emulsifier and as a dough conditioner for bread, whereas bleached starches are used for improved adhesion of batter and breading mixes in fried foods. 

Starch Oxidation. In order to produce starch derivatives with improved water dispersibilities and reduced retrogradation potential two oxidative reagents were tested sodium hypoch-... 

Although starch oxidation was still deemed worthy of investigation due to its ability to deter aqueous starch retrogradation, no starch oxidizing agent approved for food use was apparently specific enough for the production of the desired dialdehyde... 

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

The viscosity of a starch paste is often characterized differently by the starch manufacturer and by users in the paper industry. In the manufacturing plant, viscosity tests serve to control the starch modification process. As an example, the test is used to determine when to terminate a starch oxidation reaction for viscosity reduction. In the paper mill, viscosity testing is required to characterize the flow properties of starch-based coating formulations. 

However, the relatively high enzyme costs form an obstacle to commercialization. Inefficient laccase use is a result of its instability towards the oxidizing reaction conditions. We have recently shown that the stability of the laccase under reaction conditions can be improved by immobilization as a cross-linked enzyme aggregate (see Chapter 9). It has also been shown that a water-soluble iron complex of a sulfonated phthalocyanine ligand is an extremely effective catalyst for starch oxidation with hydrogen peroxide in an aqueous medium [11]. 

Stronger oxidation leads to oxidation of the C-6 atoms to carboxyl groups, as well as of the hydroxyl groups on the C-1, C-2, and C-3 atoms. " Only oxidations useM in dextrinization are considered here. Oxidized starches yield darker dextrins. More-advanced discussion ofthe problems of starch oxidation is given in the Radley monograph. ... 

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. 

Starch phosphates have been oxidized to carboxylic derivatives.1622 Starches oxidized by NaOCl could be phosphorylated with POCI3,1623 causing crosslinking. The reaction of starch phosphate with glycidyltrimethylammonium chloride gave the corresponding phosphobetaine compound, starch poly[3-(lV,lV,lV-trimethylammonio)-2-hydroxypropyl phosphate].1624... 

Borax has frequently been used in conjunction with such reagents as (3-chloro-2-hydroxypropyl)trimethylammonium salts,1853 epichlorohydrin or formaldehyde,1401185318541855 melamine-formaldehyde resins,1856 (carboxymethyl) starch, oxidized (carboxymethyl)starch, (carboxymethyl)starch-acrylamide copolymer,1857 and oxidized starch.1858 Boric acid was also used jointly with formaldehyde,1859 and starch dialdehyde has been crosslinked with boric acid.526... 

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