The ascorbic acid, total polyphenols, total anthocyanins and mineral content, together with antioxidant activity, was determined in fi ve Czech, two Ukrainian and two Austrian cultivars of cornelian cherry (Cornus mas L.) widely grown in the Czech Republic. Ascorbic acid content varied between 199-433 mg kg -1 , total polyphenols between 2174-6143 mg kg -1 , and total anthocyanins between 61-253 mg kg -1 . All fruits were good sources of major metals (K, Ca, Mg, Fe, and Mn) and trace elements (Cu, Zn, and Cr). The antioxidant activity was determined by EPR and DPPH radical scavenging assay and ranged from 29.5% to 67.2%. There was a linear relationship between antioxidant activity and total polyphenol content. Based on the obtained results, Ekotišnovský, Fruchtal, and Ruzyňský cultivars were recommended for further investigation and breeding programme of cornelian cherry fruit in the Czech Republic.
Investigation of the separability of thaumatin by capillary electrophoresisThe electrophoretic behaviour of the highly basic protein thaumatin was explored in strongly acid (pH 2) and mildly acid (pH 4.5) separation systems using both bare and coated fused silica capillaries. The separation selectivity for thaumatin I, thaumatin II, and for other sample constituents was insufficient for their baseline separation at pH 2 in an uncoated capillary because the separation efficiency was markedly lower than is common in the electrophoretic separations of proteins. A separation selectivity higher by up to one order of magnitude has been reached at pH 4.5. A pronounced asymmetry of zones, which impaired resolution at this pH, was effectively suppressed by coating of the capillary wall with a polymer. In fact, adsorption on the capillary coating always plays a contributory role whenever a good separation of thaumatin constituents is attained. This indicates that electrochromatographic separation systems based on capillaries coated with the layer of either cationic or hydrophilic uncharged polymer hold promise for the development of methods for thaumatin analysis.
People suffering from diabetes or being overweight must severely reduce their sugar use, often seeking food with sweeteners. Often, sugar is replaced by non-nutritious sweeteners in beverages, which also contain several other substances like vitamins, caffeine, amino acids, phenolic compounds and thus increasing the shelf life of the beverages is additionally treated with the addition of preservatives. As the concentration of additives in food (including beverages) is determined by the legislation in force, it is necessary to have an appropriate analytical method for food control. Since artificial sweeteners and preservatives are very different substances, they are determined separately using different HPLC methods. In this work HPLC method combining the advantages of specific (diode array detector, DAD) and universal (evaporative light scattering detector, ELSD) detector was validated and used for simultaneous determination of benzoic acid, sorbic acid, aspartame, acesulfame K, saccharin, sucralose and steviol glycosides in sugar-free beverages. The proposed analytical method showed good linearity, precision, and accuracy. Measured limits of detection (0.6 – 11.8 mg.dm-3 depending on the analyte) were sufficient to analyze 5-times diluted beverage samples. The validated method has been successfully used for the simultaneous analysis of artificial sweeteners and preservatives in beverage samples (energy drinks, ice teas, carbonated drinks). Except for steviol glycosides, the concentration of monitored substances in beverages did not exceed the maximum permitted concentrations given in the valid legislation.
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