No abstract available

[en] Seven different spices (thyme, cinnamon, coriander, caraway, pimento, paprika, black pepper) were treated by gamma radiation at an absorbed dose of 10 kGy, and the effect on chemical quality was determined. The effects of this dose were assessed by spectrophotometric analysis of some water-soluble constituents of spices (carbohydrates; carbonyl compounds) and on the content of water-insoluble steam-volatile oils. The colour of paprika and the content of piperine in pepper held in different packaging materials were measured in unirradiated and irradiated samples as a function of storage time. In all cases irradiation does not bring about any distinct qualitative or quantitative chemical changes based on spectrophotometric analysis of spice extracts. (author)

No abstract available

[en] The decomposition yield of tryptophan and radiation chemical yields of stable products - N-formylkynurenine (FK) and hydrogen peroxide (H₂O₂) were measured in oxygenated solutions at various tryptophan concentrations. A lower yield of H₂O₂ than expected was observed. However, results obtained by following the effect of pH on FK- and H₂O₂-formation indicate that the loss of H₂O₂ is due to the reaction of Trp-OH adducts with O₂^- radicals which are precursors of hydrogen peroxide. N-formyl-kynurenine is formed in the reaction of Trp-OH with both O₂^-and O₂. (author)

[en] The effect of absorbed dose on the decomposition of tryptophan under gamma irradiation has been investigated. Neutral deaerated and N₂O saturated solutions of various tryptophan concentrations were analysed. In both cases the decomposition yield of tryptophan decreases as irradiation dose increases. From the observed dependence initial yields G⁰(-Trp) = 3.35 and 4.75 were estimated for deaerated and N₂O saturated solutions respectively. Estimated initial yields are in good agreement with values calculated according to the reaction scheme proposed. (author)

[en] The effect of oxygen on the radiolysis of tyrosine in aqueous solutions was investigated by using gamma and pulsed electron irradiation. Steady-state radiolysis was reexamined and extended to include the effect of pH and determination of hydrogen peroxide. The loss of tyrosine, G(-Tyr), during irradiation and yields of 3,4-dihydroxyphenylalanine, G(DOPA), and hydrogen peroxide, G(H2O2), are determined in the pH range from 1 to 9. In the whole pH range used G(-Tyr) equals G(DOPA), and a higher G(H2O2) than expected was observed. In slightly acid and neutral media, both G(-Tyr) and G(DOPA) equal the yield of hydroxyl radicals, GOH, formed in the radiolysis of water, while the excess of hydrogen peroxide equals 1/2 GOH. Hence it was concluded that all tyrosine OH-adducts react with oxygen yielding peroxy radicals. In acid and alkaline media all measured yields decrease. This is caused by formation of tyrosine phenoxyl radicals (TyrO), which react with superoxide anion (O2-) and hydroperoxy (HO2) radicals regenerating tyrosine. By using pulse radiolysis K(TyrO + O2) less than or equal to 2 X 10(5) mol-1 dm3 s-1 and k(TyrO + O2-) = (1.7 +/- 0.2) X 10(9) mol-1 dm3 s-1 were determined. On the basis of the results, a reaction mechanism is proposed