Czech Journal of Food Sciences, 2008 (vol. 26), issue 2
Biosynthesis of food constituents: Natural pigments. Part 2 - a review
Jan Velíšek, Jiří Davídek, Karel Cejpek
Czech J. Food Sci., 2008, 26(2):73-98 | DOI: 10.17221/2463-CJFS 
This review article is a part of the survey of the generally accepted biosynthetic pathways that lead to the most important natural pigments in organisms closely related to foods and feeds. The biosynthetic pathways leading to xanthones, flavonoids, carotenoids, and some minor pigments are described including the enzymes involved and reaction schemes with detailed mechanisms.
Degradation of α-galactosides during the germination of grain legume seeds
Pavel KADLEC, Jana DOSTÁLOVÁ, Jana BERNÁŠKOVÁ, Michaela SKULINOVÁ
Czech J. Food Sci., 2008, 26(2):99-108 | DOI: 10.17221/3/2008-CJFS
Germination is one of the most effective ways of preparing grain legumes for consumption. Because it involves the total or partial elimination of some anti-nutritional compounds, it is also one of the simplest methods of enhancing the palatability of grain legumes, thereby increasing their consumption as a valuable source of nutrition. The main objective of this paper is to describe the changes that take place in α-galactosides during germination. During germination, galactose molecules gradually become detached from α-galactosides due to the effect of the enzyme α-D-galactosidase activated during the process. To simulate the degradation...
Image vision technology for the characterisation of shape and geometrical properties of two varieties of lentil grown in Turkey
Ebru Firatligil-Durmuş, Evžen Šárka, Zdeněk Bubník
Czech J. Food Sci., 2008, 26(2):109-116 | DOI: 10.17221/1/2008-CJFS
Geometrical features of lentil seeds (Lens culinaris Medik) were analysed using the image analysis LUCIA system Ver. 3.52. The values of the weight of 1000 kernels, kernel density, specific volume, specific surface area, and surface area of 1000 kernels of red and green lentils were determined as 66.61 and 138.56 g, 1504.5 and 1376.4 kg/m3, 0.6647 and 0.7265 cm3/g, 0.594 and 0.579 m2/kg, 395.4 and 801.9 cm2,, respectively. The lentil volume was simulated by an oblate spheroid and two sphere segments and the volumes obtained with both models were compared with that obtained by pycnometric method. Percentage...
Formation of carboxylic acids during degradation of monosaccharides
Ondřej Novotný, Karel Cejpek, Jan Velíšek
Czech J. Food Sci., 2008, 26(2):113-131 | DOI: 10.17221/2465-CJFS
The formation of low molecular carboxylic and hydroxycarboxylic acids as well as sugar and deoxysugar acids from monosaccharides (D-glucose, D-fructose, D-arabinose, DL-glyceraldehyde, and 1,3-dihydroxyacetone) was studied in three different model systems: aqueous and alkaline solutions of potassium peroxodisulfate (K2S2O8), and sodium hydroxide solution. In total, 3 low molecular carboxylic acids (formic, acetic and propionic), 24 hydroxycarboxylic acids, and 12 corresponding lactones were identified and quantified by GC/MS. Formic, acetic, and propionic acids were isolated by extraction with diethyl ether and directly...
Czech medicinal plants as possible sources of antioxidants
Lucie BUŘIČOVÁ, Zuzana RÉBLOVÁ
Czech J. Food Sci., 2008, 26(2):132-138 | DOI: 10.17221/2468-CJFS
The antioxidant activity of 17 Czech medicinal plants was studied and compared with the antioxidant activity of green tea. The antioxidant activities of water and ethanol extracts of the plants tested were determined by a spectrophotometric method using the stable free radical DPPH (2,2-diphenyl-1-picrylhydrazyl), and further the contents of the compounds with reducing properties in water extracts were determined by flow injection analysis with amperometric detection (using a detection potential +0.7 V). Considerable antioxidant activities were found in the extracts of plants from the Rosaceae family (rosehips and leaves of raspberry, blackberry,...
Effect of ethanol on interactions of bitter and sweet tastes in aqueous solutions
Zdeňka PANOVSKÁ, Alena ŠEDIVÁ, Markéta JEDELSKÁ, Jan POKORNÝ
Czech J. Food Sci., 2008, 26(2):139-145 | DOI: 10.17221/2466-CJFS
Experimental samples simulated the composition of vermouths. In all experiments, 0.01% quinine was used as a standard bitter substance. Sucrose increased the acceptability in the concentration range of up to 14%, remaining constant at higher concentrations, both in aqueous and 16% ethanolic solutions. A decrease of bitterness was observed in water but not in 16% ethanol. Ethanol did not affect the sweetness appreciably at the concentrations of up to 16%, but 32% ethanolic solutions appeared less sweet. Ethanol enhanced the bitterness only at high concentrations; interactions were similar in the samples containing 10% and 16% sucrose. Aspartame and...
HPLC-MS/MS method for analysis of isoproturon in difficult matrix: poppy seeds
Tomáš Kovalczuk, Jan Poustka, Jana Hajšlová
Czech J. Food Sci., 2008, 26(2):146-152 | DOI: 10.17221/2469-CJFS
While several validated methods have been developed for analysis of phenylurea herbicides in staple food plants, analytical procedures suitable for their quantification in minor crops such as poppy seeds are not available. For the registration of isoproturon use in this crop, the documentation of dynamics of its residues following treatment was requested. To accomplish this task, HPLC-MS/MS method was developed. Extraction of residues was realised by methanol-water mixture, Supelclean LC-18 SPE cartridges were used for purification of crude extracts. For HPLC separation of isoproturon SPE fraction Lichrospher C18 column (25 cm × 4 mm, 5 μm) was...