Czech Journal of Food Sciences, 2001 (vol. 19), issue 1
Influence of cheese ripening on the viscoelastic behaviour of edam cheese
J. Buchar, I. Kubiš, S. Gajdůšek, I. Křivánek
Czech J. Food Sci., 2001, 19(1):1-7 | DOI: 10.17221/6566-CJFS 
The paper deals with the study of the effect of cheese ripening on parameters of a rheological model of cheese mechanical behaviour. The Edam cheese has been tested by the method of the Hopkinson Split Pressure Bar. The original method of the evaluation of viscoelastic properties has been used. The rheological model of the three element linear viscoelastic body, so called "standard linear solid" has been used. This model successfully describes the experimentally observed deformation behaviour of cheese specimens. The effect of the time of cheese ripening on the parameters of the rheological model has been demonstrated.
Determination of aflatoxins in food products by the ELISA method
J. Leszczyńska, J. Masłowska, A. Owczarek, U. Kucharska
Czech J. Food Sci., 2001, 19(1):8-12 | DOI: 10.17221/6567-CJFS
To determine the total content of aflatoxins, aflatoxin B1 and aflatoxin M1 in food the ELISA method was used. Milk, dairy products and cereal samples were mainly investigated. A few samples were found to be contaminated with aflatoxins. A great usability of the ELISA method for aflatoxin determination in food was established. Selectivity and sensitivity of the method is reported.
Novel Strecker degradation products of tyrosine and dihydroxyphenylalanine
J. Adamiec, K. Cejpek, J. Rössner, J. Velíšek
Czech J. Food Sci., 2001, 19(1):13-18 | DOI: 10.17221/6568-CJFS
Tyrosine was oxidised with either potassium peroxodisulphate or glyoxal. Volatile reaction products were isolated and analysed by GC/FID and GC/MS, derivatised with diazomethane and analysed by the same methods. Eight reaction products were identified. The major products were the expected Strecker aldehyde (4-hydroxyphenylacetaldehyde) and its lower homologue 4-hydroxybenzaldehyde. They were followed by 1-(4-hydroxyphenyl)-3-propionaldehyde, phenylacetaldehyde, benzaldehyde, phenol, 4-hydroxybenzoic, and benzoic acid. Analogously, the oxidation of 3,4-dihydroxyphenylalanine yielded the corresponding Strecker aldehyde (3,4-dihydroxyphenylacetaldehyde),...
Determination of oxidative stability in mixtures of edible oil with nonlipidic substances
L. Trojáková, Z. Réblová, Z. Pokorný
Czech J. Food Sci., 2001, 19(1):19-23 | DOI: 10.17221/6569-CJFS
The storage of lipid foods is mostly affected by the oxidation of lipid fraction. Dry foods are particularly sensitive because lipids are not protected by hydrated proteins against oxidation. A method suitable for testing dry foods was studied in model mixtures of rapeseed oil with albumin or cellulose. Oxipres apparatus was used, where the course of oxidation is monitored by changes of oxygen pressure. The end of induction period was more evident than in bulk oils as the contact of lipids with oxygen is better. The induction period was longer in mixtures of edible oil with albumin than in mixtures with cellulose. The induction period moderately decreased...
Changes during the extrusion of semolina in mixture with sugars
A. Farouk Mansour, F. Pudil, V. Janda, J. Pokorný
Czech J. Food Sci., 2001, 19(1):24-30 | DOI: 10.17221/6570-CJFS
Wheat semolina and its mixtures with 5% glucose, fructose of sucrose were processed in a sigle screw extruder at the maximum temperature of 140°C and the processing time of 30 s. The nonenzymic browning was only moderate, but it was substantially more intensive in mixtures with glucose or fructose than in the case of wheat semolina or its mixture with sucrose. Red and yellow pigments were mainly formed. The odour acceptability was affected by the presence of sugars almost negligibly, but the intensities were different, higher in extruded mixtures with glucose and fructose than in wheat semolina or its mixture with sucrose. Small differences were observed...
Determination of essential oils content and composition in caraway (Carum carvi L.)
J. Sedláková, B. Kocourková, V. Kubáň
Czech J. Food Sci., 2001, 19(1):31-36 | DOI: 10.17221/6571-CJFS
Total content and composition of essential oils in caraway seed (Carum carvi L.) from a selection of caraway varieties grown in different production areas were determined after supercritical fluid extraction (SFE) and steam distillation. Different procedures of sample pretreatment (homogenization) and methods of isolation were compared from the point of view of efficiency, reproducibility and accuracy. The effect of storage period was also examined.
Antibacterial activity of houttuynin sodium bisulphate (HSB)
L. Kokoška, V. Rada
Czech J. Food Sci., 2001, 19(1):37-40 | DOI: 10.17221/6572-CJFS
Houttuynin sodium bisulphate (HSB), a-hydroxyl-capryl-ethyl-sodium-sulphonate, is a product formed by reacting sodium bisulphate with houttuynin, which is obtained from a medicinal herb Houttuynia cordata Thunb. The antibacterial activity of HSB was measured by optical density. Minimum inhibitory concentrations at 50% and 90% inhibition level (MIC50 and MIC90) for Escherichia coli varied from 0.5 to 0.6 mg/ml and from 2.6 to 2.7 mg/ml, respectively. For Staphylococcus aureus MIC50 and MIC90 varied from 0.2 to 0.3 mg/ml and from 0.4 to 0.5 mg/ml, respectively. In comparison with MIC of antibiotics currently used for...