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This study contains data of seven blue cultivars of table grape (Vitis vinifera L. and Vitis labrusca L.): Attika, Early Cardinal, Eszter, Chasselas rosé, Königliche Esther, Muscat bleu, and Nero. The following were determined in intact berries: malic, tartaric, and titratable acids, pH values, sugar content, and antioxidant capacity. Concentrations of the following compounds were determined in the pulp of analysed berries: phenolic acids and catechins. The last analysis focused on skins; in addition to the same phenolic acids and catechins, excluding epicatechin, analysed from pulp; ferulic acid and stilbenes were also studied. Higher contents of procyanidin B2 and gallic acid were found in the pulp as compared to those found in skins. Studies during the ripening stage showed that the higher ratio of procyanidin B2 and gallic acid concentrations in the pulp vs. skins relates to late-ripening cultivars, while for early-ripening cultivars a lower ratio was observed. Contents of phenolic acids, catechin, stilbenes, and anthocyanins were studied by means of LC-DAD; other compounds were measured by FTIR.

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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.

Open access
Acta Alimentaria
Authors: E. Tománková, J. Balík, I. Soural, P. Bednář, and B. Papoušková

This study presents findings from comparing the properties of anthocyanin pigments: i. malvidin-3-glucoside (Mal-3-G), the most significant anthocyanin present in young red wine; ii. Vitisin A (5-carboxypyranomalvidin-3-glucoside), a major product from a reaction induced in red wine between Mal-3-G and pyruvic acid during its ageing. These pigments were determined and compared to the absorption spectrum in 200–770 nm at various pH values, such results including the ability of cation Al3+ to change the values of absorbance. Changes in the colour parameters L* a* b* were determined in the CIELAB colour space of Mal-3-G and Vitisin A in relation to pH and the addition of AlCl3. Both coloured compounds were investigated for their resistance to discoloration by sulphur dioxide. Total antioxidant activity was evaluated by two methods (FRAP, DPPH), and the values were compared to other phenols.

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Acta Alimentaria
Authors: L. Červinka, P. Burg, I. Soural, V. Mašán, A. Čížková, J. Souček, V. Višacki, O. Ponjičan, and A. Sedlar

Abstract

Sauvignon Blanc represents an important grape variety. The wine made from this variety is known to have a wide range of aroma profiles from nettles to tropical fruits. Beside the raw material quality (grapes), the quality of wines can be fundamentally influenced by the technological conditions applied in the wine making process. Yeast and other microorganisms play a key role in the formation of metabolites during alcoholic fermentation. In this study, the effects of autochthonous or selected wine yeasts (Saccharomyces cerevisiae) and fermentation temperatures (15 °C and 19 °C) were tested on major monoterpenes contents of wines during the period 2016–2017. The obtained values show that the highest contents of linalool (24.36 μg L−1) and hotrienol (11.84 μg L−1) were determined in wine samples produced with active (selected) wine yeast at lower temperature. Sensory evaluation results indicated that monoterpenes can have a positive effect on the overall sensory quality of Sauvignon Blanc wines, despite the fact that their determined concentrations in the evaluated samples were not higher than their threshold values.

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