Template-Type: ReDIF-Article 1.0 Author-Name: J. Buchar Author-Workplace-Name: Mendel University of Agriculture and Forestry Department of Physics and Department of Food Technology, Brno, Czech Republic Author-Name: I. Kubiš Author-Workplace-Name: Mendel University of Agriculture and Forestry Department of Physics and Department of Food Technology, Brno, Czech Republic Author-Name: S. Gajdůšek Author-Workplace-Name: Mendel University of Agriculture and Forestry Department of Physics and Department of Food Technology, Brno, Czech Republic Author-Name: I. Křivánek Author-Workplace-Name: Mendel University of Agriculture and Forestry Department of Physics and Department of Food Technology, Brno, Czech Republic Title: Influence of cheese ripening on the viscoelastic behaviour of edam cheese Abstract: 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. Keywords: Edam cheese, ripening, standard model, model parameters, sensory evaluation Journal: Czech Journal of Food Sciences Pages: 1-7 Volume: 19 Issue: 1 Year: 2001 DOI: 10.17221/6566-CJFS File-URL: http://cjfs.agriculturejournals.cz/doi/10.17221/6566-CJFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/cjf-200101-0001.txt Handle: RePEc:caa:jnlcjf:v:19:y:2001:i:1:id:6566-CJFS Template-Type: ReDIF-Article 1.0 Author-Name: J. Leszczyńska Author-Workplace-Name: Technical University of Lódž - Bioinorganic and Analytical Chemistry Group, Institute of General Food Chemistry, Lódž, Poland Author-Name: J. Masłowska Author-Workplace-Name: Technical University of Lódž - Bioinorganic and Analytical Chemistry Group, Institute of General Food Chemistry, Lódž, Poland Author-Name: A. Owczarek Author-Workplace-Name: Technical University of Lódž - Bioinorganic and Analytical Chemistry Group, Institute of General Food Chemistry, Lódž, Poland Author-Name: U. Kucharska Author-Workplace-Name: Technical University of Lódž - Bioinorganic and Analytical Chemistry Group, Institute of General Food Chemistry, Lódž, Poland Title: Determination of aflatoxins in food products by the ELISA method Abstract: 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. Keywords: aflatoxins, ELISA, immunoenzymatic method Journal: Czech Journal of Food Sciences Pages: 8-12 Volume: 19 Issue: 1 Year: 2001 DOI: 10.17221/6567-CJFS File-URL: http://cjfs.agriculturejournals.cz/doi/10.17221/6567-CJFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/cjf-200101-0002.txt Handle: RePEc:caa:jnlcjf:v:19:y:2001:i:1:id:6567-CJFS Template-Type: ReDIF-Article 1.0 Author-Name: J. Adamiec Author-Workplace-Name: Institute of Chemical Technology - Department of Food Chemistry and Analysis, Prague, Czech Republic Author-Name: K. Cejpek Author-Workplace-Name: Institute of Chemical Technology - Department of Food Chemistry and Analysis, Prague, Czech Republic Author-Name: J. Rössner Author-Workplace-Name: Institute of Chemical Technology - Department of Food Chemistry and Analysis, Prague, Czech Republic Author-Name: J. Velíšek Author-Workplace-Name: Institute of Chemical Technology - Department of Food Chemistry and Analysis, Prague, Czech Republic Title: Novel Strecker degradation products of tyrosine and dihydroxyphenylalanine Abstract: 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), its lower homologue 3,4-dihydroxybenzaldehyde, 3,4-dihydroxybenzoic, 3,4-dihydroxyphenylacetic, and caffeic acid. An identification of these oxidation products of tyrosine and 3,4-dihydroxyphenylalanine assumes homolytic cleavage of the Strecker aldehydes and a recombination of free radicals formed by this cleavage. As minor products, six O- and N-heterocyclic compounds arose in systems containing glyoxal (pyrazine, methyl- and ethylpyrazine, 3-furancarbaldehyde, 5-methyl-2-furancarbaldehyde, 2-pyrrolcarbaldehyde). Keywords: Strecker degradation, amino acids, glyoxal, sodium peroxodisulphate, radicals, tyrosine, 3, 4-dihydroxyphenyl-alanine (DOPA), 4-hydroxyphenylacetaldehyde, 4-dihydroxyphenylacetaldehyde Journal: Czech Journal of Food Sciences Pages: 13-18 Volume: 19 Issue: 1 Year: 2001 DOI: 10.17221/6568-CJFS File-URL: http://cjfs.agriculturejournals.cz/doi/10.17221/6568-CJFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/cjf-200101-0003.txt Handle: RePEc:caa:jnlcjf:v:19:y:2001:i:1:id:6568-CJFS Template-Type: ReDIF-Article 1.0 Author-Name: L. Trojáková Author-Workplace-Name: Institute of Chemical Technology - Department of Food Chemistry and Analysis, Prague, Czech Republic Author-Name: Z. Réblová Author-Workplace-Name: Institute of Chemical Technology - Department of Food Chemistry and Analysis, Prague, Czech Republic Author-Name: Z. Pokorný Author-Workplace-Name: Institute of Chemical Technology - Department of Food Chemistry and Analysis, Prague, Czech Republic Title: Determination of oxidative stability in mixtures of edible oil with nonlipidic substances Abstract: 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 with increasing oxygen pressure, while the effect of sample weight was nearly negligible. The induction period length was a semilogarithmic function of reaction temperature. Variation coefficients and differences between the duplicates showed good reproducibility; they were lower in mixtures with albumin than in mixtures with cellulose, but both were of the same order as the respective values in bulk oils. At 120°C and 0.5 MPa oxygen, the induction periods could be usually measured within a working day. Keywords: albumin, autoxidation, cellulose, edible oils, Oxipres apparatus, stability against oxidation Journal: Czech Journal of Food Sciences Pages: 19-23 Volume: 19 Issue: 1 Year: 2001 DOI: 10.17221/6569-CJFS File-URL: http://cjfs.agriculturejournals.cz/doi/10.17221/6569-CJFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/cjf-200101-0004.txt Handle: RePEc:caa:jnlcjf:v:19:y:2001:i:1:id:6569-CJFS Template-Type: ReDIF-Article 1.0 Author-Name: A. Farouk Mansour Author-Workplace-Name: Institute of Chemical Technology - Department of Food Chemistry and Analysis, Prague, Czech Republic Author-Name: F. Pudil Author-Workplace-Name: Institute of Chemical Technology - Department of Food Chemistry and Analysis, Prague, Czech Republic Author-Name: V. Janda Author-Workplace-Name: Institute of Chemical Technology - Department of Food Chemistry and Analysis, Prague, Czech Republic Author-Name: J. Pokorný Author-Workplace-Name: Institute of Chemical Technology - Department of Food Chemistry and Analysis, Prague, Czech Republic Title: Changes during the extrusion of semolina in mixture with sugars Abstract: 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 in the sensory profile. Extrusion of semolina with sugars produced more sensory active volatiles (52-69 identified compounds) than in extruded semolina (41 compounds). Pyrazines, furans and pyrans were the most important sensory active compounds. Their amounts increased by the addition of sugars to semolina; the mixture of semolina with glucose was particularly rich in active compounds. The formation of pyrazines was more enhanced by the addition of fructose than of other sugars. Maltol, butyrolactone and acetic acid were present in large amounts. Even if sensory characteristics were improved by addition of sugars to semolina, the difference was not very pronounced. Keywords: browning, extrusion, furans, fructose, glucose, pyrazines, semolina, sensory value, sucrose, wheat Journal: Czech Journal of Food Sciences Pages: 24-30 Volume: 19 Issue: 1 Year: 2001 DOI: 10.17221/6570-CJFS File-URL: http://cjfs.agriculturejournals.cz/doi/10.17221/6570-CJFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/cjf-200101-0005.txt Handle: RePEc:caa:jnlcjf:v:19:y:2001:i:1:id:6570-CJFS Template-Type: ReDIF-Article 1.0 Author-Name: J. Sedláková Author-Workplace-Name: Mendel University of Agriculture and Forestry in Brno - Department of Chemistry and Biochemistry Author-Name: B. Kocourková Author-Workplace-Name: Mendel University of Agriculture and Forestry in Brno - Department of Chemistry and Biochemistry Author-Name: V. Kubáň Author-Workplace-Name: Mendel University of Agriculture and Forestry in Brno - Department of Chemistry and Biochemistry Title: Determination of essential oils content and composition in caraway (Carum carvi L.) Abstract: 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. Keywords: carvone, limonene, Carum carvi L., steam distillation, supercritical fluid extraction (SFE), gas chromatography Journal: Czech Journal of Food Sciences Pages: 31-36 Volume: 19 Issue: 1 Year: 2001 DOI: 10.17221/6571-CJFS File-URL: http://cjfs.agriculturejournals.cz/doi/10.17221/6571-CJFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/cjf-200101-0006.txt Handle: RePEc:caa:jnlcjf:v:19:y:2001:i:1:id:6571-CJFS Template-Type: ReDIF-Article 1.0 Author-Name: L. Kokoška Author-Workplace-Name: 2 LADISLAV KOKOŠKA and VOJTÌCH RADA Author-Name: V. Rada Author-Workplace-Name: 2 LADISLAV KOKOŠKA and VOJTÌCH RADA Title: Antibacterial activity of houttuynin sodium bisulphate (HSB) Abstract: 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 treatment of disorders caused by S. aureus or by E. coli were MICs of HSB relatively high and general antibacterial activity very weak. Keywords: houttuynin sodium bisulphate, Houttuynia cordata, antibacterial activity, Escherichia coli, Staphylococcus aureus Journal: Czech Journal of Food Sciences Pages: 37-40 Volume: 19 Issue: 1 Year: 2001 DOI: 10.17221/6572-CJFS File-URL: http://cjfs.agriculturejournals.cz/doi/10.17221/6572-CJFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/cjf-200101-0007.txt Handle: RePEc:caa:jnlcjf:v:19:y:2001:i:1:id:6572-CJFS