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5. Different values obtained by the FRAP method for the determination of slowly and rapidly reacting phenols.

Author

Soural, I., Švestková, P., Híc, P., and Balík, J.

Subjects
SYRINGIC acid, PHENOLS, OXIDANT status, PHENOL, GALLIC acid, CAFFEIC acid
Abstract

A number of methods have been applied to measure total antioxidant capacity (TAC), including FRAP, which is based on reducing the amount of iron ions in a complex compound. Researchers often use measurement of absorbance 10 min after mixing a sample with the FRAP reaction solution to calculate TAC. The FRAP solution has been shown to alter absorbance over time by ca 0.0010–0.0020 per hour, under storage conditions. This article intends to show that some substances do not fully or sufficiently react within the common analysis period. It is evident from the results that some substances react more quickly and others very slowly. Absorbance in relation to various phenols was measured. Compared to the levels of absorbance at 10 min, mean absorbance at 48 h was higher by 5,395% for vanillin, 426% for caffeic acid, 170% for sinapinic acid, 67% for gallic acid, 19% for syringic acid, and only by 4% for Trolox. Results for vanillin and caffeic acid indicate potential auto-catalysis. [ABSTRACT FROM AUTHOR]

Published
2022
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23. Relation between nitrogen nutrition index and production of spring malting barley.

Author

Sedlář, O., Balík, J., Černý, J., Kulhánek, M., and Vašák, F.

Subjects
*MALTING, *BARLEY, *EFFECT of nitrogen on plants, *PLANT biomass, *DRY matter content of plants
Abstract

Although the nitrogen nutrition index (NNI) is a widely used indicator of plant nitrogen status, no model of NNI calculation for spring barley (Hordeum vulgare) reflecting also specific malting requirements of grain has been published. The aim of this study was to determine an optimal range of the nitrogen nutrition index (ratio of nitrogen concentration in shoot biomass to critical nitrogen concentration) with respect to optimal grain protein content (N × 6.25 = 9.0 - 11.5%), plump grain (grain > 2.5 mm) yield and lodging of spring malting barley during 7-year (2007 - 2013) strict field experiments realized under the conditions of three experimental sites in the Czech Republic. A dose of 80 kg N/ha and 130 kg N/ha, respectively, was applied in mineral fertilizers. The nitrogen nutrition index was determined at the BBCH 30 (beginning of stem elongation) and BBCH 45 (late boot stage) growth stages. The most suitable indicators for evaluation of the nitrogen concentration in shoot biomass of the spring malting barley in our experiments proved to be Justes et al.'s model Nc = 5.35 DM(-0.442) designated for winter wheat and Zhao's model Nc = 4.76 DM(-0.39) designated for winter barley, where DM is shoot dry matter in t/ha. The nitrogen nutrition index for spring malting barley should not exceed a value of NNI = 0.80 and NNI = 0.90 using the Justes et al.'s model and the Zhao's one during the BBCH 30 - 45 growth stages. [ABSTRACT FROM AUTHOR]

Published
2017
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31. Comparison of some physico-chemical parameters of kiwiberry (Actinidia arguta) cultivars from a cold climate

Author

Horák Miroslav, Šnurkovič Petr, Ondrášek Ivo, Balík Josef, and Srilaong Varit

Subjects
actinidia arguta, kiwiberry, antioxidant activity, ascorbic acid, skin, Plant culture, SB1-1110
Abstract

The Actinidia genus includes a number of commercial fruit species with a wide range of countries of origin. Some species such as A. arguta or A. kolomikta are characterized by a high level of resistance to frost. The aim of this study was to compare the fruit of selected cultivars of kiwiberry. In the kiwiberry fruit, sucrose was the predominant type of sugar. Citric acid was dominant in all samples; it was most represented in the pulp of kiwiberry seedlings and in the skin of kiwiberry ‘Issai’. Kiwiberry fruits feature a higher ascorbic acid content in the skin in comparison with the commercial A. chinensis cultivars. Antioxidant activity of kiwiberry fruit skin was up to 18 times higher than that of the pulp. In view of the kiwiberry fruit having no hair, it is possible to eat the whole fruit, including the skin containing substances beneficial to health.

Published
2019
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