Starch irradiation

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. 

Irradiation. Irradiation was conducted in a Co source at a dose rate of about 4 X 10 rep per hour. Preirradiated starch was prepared by irradiation of starch under vacuum in a tube fitted with a break-off tip. The monomer was added to the tube after irradiation and freed from air, using the freeze-thaw technique. Then the tube was sealed and the tip broken, thus allowing the monomer to saturate the starch. For starch irradiated in the presence of monomer, the materials were thoroughly mixed, charged to a tube, evacuated using the freeze-thaw method, and immediately irradiated. 

Dichromated Resists. The first compositions widely used as photoresists combine a photosensitive dichromate salt (usually ammonium dichromate) with a water-soluble polymer of biologic origin such as gelatin, egg albumin (proteins), or gum arabic (a starch). Later, synthetic polymers such as poly(vinyl alcohol) also were used (11,12). Irradiation with uv light (X in the range of 360—380 nm using, for example, a carbon arc lamp) leads to photoinitiated oxidation of the polymer and reduction of dichromate to Ct(III). The photoinduced chemistry renders exposed areas insoluble in aqueous developing solutions. The photochemical mechanism of dichromate sensitization of PVA (summarized in Fig. 3) has been studied in detail (13). 

Etherification and esterification of hydroxyl groups produce derivatives, some of which are produced commercially. Derivatives may also be obtained by graft polymerization wherein free radicals, initiated on the starch backbone by ceric ion or irradiation, react with monomers such as vinyl or acrylyl derivatives. A number of such copolymers have been prepared and evaluated in extmsion processing (49). A starch—acrylonitrile graft copolymer has been patented (50) which rapidly absorbs many hundred times its weight in water and has potential appHcations in disposable diapers and medical suppHes. 

Glucose, glycerol, sucrose, starch, acetate, malate and lactate were examined for the effect of carbon sources on the hydrogen production and the effects of light intensity were also examined under the different irradiances, such as 0, 3, 7, 15, 30, 50 and 110 klux/m2, by adjusting the distance between the light source and the samples of Rb. sphaeriodes KD 131 cultures. 

R. KizU and J. Irudayaraj, Discrimination of irradiated starch gels Using FT-Raman spectroscopy and chemomet-rics, J. Agric. Food Chem., 54, 13-18 (2006). 

Kizil, R. Irudavaraj, J. Seetharaman, K. Characterization of Irradiated Starches by using FT-Raman and FTIR Spectroscopy. J. Agric. Food Chem. 2002, 50, 3912-3918. 

Because ionizing radiation is a powerful sterilizing agent, food chemists became interested in this technique. Studies were mainly directed towards starch and its degradation.81,82,85-67 89 71 22 323-344 The question of the wholesomeness of irradiated food has also been considered.345-348 For a review, see Ref. 14. 

IV. Irradiation of Starch with Neutrons, X-Rays, High-Energy Electrons, and y-Rays. 263... 

Periodate Oxidation of Nonmodifled, Dextrinized, and y-Irradiated Starch ... 

Several reviews of this subject had been published until 1974.68-72 Free-radical reactions of saccharides have also been reviewed.73 Comparative studies involving X-ray, /3 (electron)-, and 7-irradiation of starch show that the results of such procedures are similar, but not identical. All of them lead to destruction of... 

Potato, com, and wheat starch was irradiated with 9 X 1014 neutrons/cm2. Neutrons cause only a weak peptonizing effect in comparison with 7-rays (2 X 106 rep) (see Table VIII). In the first case, starch becomes radioactive. Radioactive nuclei in starch are mostly phosphate isotopes and only to a very minor extent 14C. The behavior of starch of all three origins in respect to both types of irradiation is nonuniform. Generally neutron radiation does not eliminate phosphoric moieties from starch and is less destructive.77... 

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