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248 258 Chen, E. L., Chen, Y. A., Chen, L. M., Liu, Z. H. (2002) Effect of copper on peroxidase activity and lignin content in Raphanus sativus . Plant Physiol. Biochem

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p. Marjamaa, K., Lehtonen, M., Lundell, T., Toikka, M., Saranpaa, P., Fagerstedt, Kurt, V. (2003) Developmental lignification and seasonal variation in β-glucosidase and peroxidase activity in xylem of Scots

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Onion peroxidase (POD) has been known to act on some o-diphenol acids, such as caffeic and hydrocaffeic acid, but data on monophenols are rather scarce. This study is aimed to investigate the use of a crude peroxidase preparation from onion solid wastes for oxidising p-coumaric acid, a widespread phenolic acid, various derivatives of which may occur in foods. The highest enzyme activity was observed at a pH value of 5, but considerable activity was also retained for pH up to 6. Favourable temperatures for increased activity varied between 30 and 50 °C, 40 °C being the optimal. Liquid chromatography/mass spectrometry analysis of a POD-treated p-coumaric acid solution showed the formation of two major products, which were identified as a p-coumaric acid dimer and a decarboxylated dehydrotetramer. The putative oxidation pathway proposed shares common features with those reported for other hydroxycinnamates.

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Millet (Panicum miliaceum L.) is more resistant to climatic and soil conditions but the yields are lower than in wheat (Triticum aestivum L.), therefore its cultivation was given up for decades in Hungary. Millet is a suitable raw material for the production of pasta products without using eggs and it has other advantageous physiological effects, therefore its cultivation in Hungary is expected again. Millet is a gluten free cereal so it is not able to create viscoelastic protein network. During the biochemical studies the activity of enzymes (peroxidase, polyphenol oxidase) influencing the colour of the flour, flour mixtures (T. aestivum L., Triticum durum L., P. miliaceum L.), and pasta products were examined. Oxidoreductases in wheat flour have always been of interest to cereal chemists. The effects of peroxidase (EC 1.11.1.7) (POX) are much less thoroughly documented, although they are reported to have a relatively high level of activity in different flours. These days there are also insufficient research data on how the millet in dry pasta modifies the enzyme activity and the storage stability and shelf life of dry pasta products.

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A study on the germination of five Vicia faba cultivars exposed to polyethylene glycol-induced water stress indicated that cv Giza 40 showed the highest germination capacity and cv Giza 667 the lowest. The effect of low soil water content was studied on the plant growth, photosynthetic pigment content, organic solutes, relative water content (RWC), lipid peroxidation, membrane stability index (MSI), and the catalase (CAT) and peroxidase (POX) activity in the leaves of 21-day-old Vicia faba cv Giza 40 and cv Giza 667 plants. With respect to dry weight (DW), drought caused a greater decrease in cv Giza 667 than in cv Giza 40, indicating that cv Giza 40 was more tolerant of low soil water content. Drought decreased the Chl a, Chl b and carotenoid contents and the Chl a/b and carotenoid/Chl a+b ratios in the leaves of cv Giza 667, while in cv Giza 40 a significant increase in these pigment parameters was observed under drought stress. Drought caused a decrease in RWC and MSI and an increase in the lipid peroxidation level and in the catalase (CAT) and peroxidase (POX) activity in both the cultivars, but the decline in RWC and MSI and the increase in lipid peroxidation level in response to drought stress were greater in cv Giza 667 than in cv Giza 40. The CAT and POX activities were higher in Giza 40 than in Giza 667 under both control and drought conditions. Drought induced the accumulation of soluble sugars, soluble proteins, free amino acids and proline in both cultivars. However, this accumulation was lower in cv Giza 667 than in the more tolerant cv Giza 40. These results indicate that cv Giza 40 showed better protection against drought-induced oxidative stress through higher CAT and POX activities and osmolyte concentrations than cv Giza 667.

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Peroxidase (POD) and lipoxygenase (LOX) inactivation temperature and time were investigated on broccoli florets at different blanching treatments. In addition, retention of nutritional components,which reduced POD and LOX activities, was compared. LOX inactivation required 14 min at 70 °C, 6 min at 80 °C, 11/2 min at 90 °C, 1 min at 100 °C water blanching and 1 min for steam blanching, 2 min in microwave without water and 6 min with microwave and water. The highest nutritional content of broccoli was evaluated in microwave blanching without water by comparison to all treatments. The decline of nitrate and nitrite value of broccoli was higher under longer time blanching than under higher temperature blanching.

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-bound peroxidase activities with growth in anoxiatreated rice ( Oryza sativa L.) coleoptiles and roots . Plant Sci. 106 : 1 – 7 . Lin , C.C. , Kao , C.H. 2001 . Cell wall

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248 258 Chen, E. L., Chen, Y. A., Chen, L. M., Liu, Z. H. (2002) Effect of copper on peroxidase activity and lignin content in Raphanus sativus . Plant Physiol. Biochem

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. Comparative Vertebrate Endocrinology 1998 Bhattacharya, S., Datta, A. K. (1971) A comparative study of the peroxidases from

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Van der Westhuizen, A.J., Qian, X-M., Botha, A-M. 1998a. Differential induction of apoplastic peroxidase and chitinase activities in susceptible and resistant wheat cultivars by Russian wheat aphid infestation. Plant Cell Reports 18 :132

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