Czech Journal of Food Sciences, 2002 (vol. 20), issue 5
Optical isomers of chloropropanediols: mechanisms of their formation and decomposition in protein hydrolysates
J. Velíšek, M. Doležal, C. Crews, T. Dvořák
Czech J. Food Sci., 2002, 20(5):161-170 | DOI: 10.17221/3527-CJFS 
Protein hydrolysates produced by hydrochloric acid hydrolysis were analysed for 3-chloropropane-1,2-diol and its enantiomers. It was found that (R)-3-chloropropane-1,2-diol and (S)-3-chloropropane-1,2-diol were present in the hydrolysates in equimolar concentrations. Model experiments with glycerol, triolein and soy lecithin heated with hydrochloric acid in solution showed that these materials were precursors of 3-chloropropane-1,2-diol and 2-chloropropane-1,3-diol and, as expected, yielded racemic 3-chloropropane-1,2-diol. Yields of 3-chloropropane-1,2-diols decreased in the order triolein > lecithin > glycerol. The mechanisms...
Comparison of four methods for identification of bifidobacteria to the genus level
E. Vlková, J. Medková, V. Rada
Czech J. Food Sci., 2002, 20(5):171-174 | DOI: 10.17221/3528-CJFS
The identification of bifidobacteria to the genus level is important for the differentiation of these bacteria from other bacteria occurring in the animal and human intestine. The detection of fructose-6-phosphate phosphoketolase (F6PPK-test) is used traditionally for the identification of Bifidobacterium sp. The original procedure is time consuming and therefore it was modified several times recently. The aim of the present work was to compare the following methods for the genus identification of bifidobacteria: F6PPK-test, F6PPK-test modified by the addition of triton X-100, F6PPK-test modified by the addition of cetridium bromide (F6PPK-CTAB-test),...
Histometric evaluation of meat products - determination of size and number of objects
B. Tremlová, P. Štarha
Czech J. Food Sci., 2002, 20(5):175-180 | DOI: 10.17221/3529-CJFS
In the framewort of the quantitative histologic evaluation of poultry products, the size and the number of bone fragments have been determined using the image analysis. Bone fragments were identified by their colour and analysed automatically. The samples contained 135 to 2167 bone particles the length of which varied from 5 to 2088 μm. Comparing products of the same kind, we found differences in the contents of bone fragments; this fact was possibly due to inadequate observance of the technological procedure by some producers.
Antimutagenic effect of ellagic acid and its effect on the immune response in mice
P. Šmerák, H. Šestáková, Z. Polívková, I. Bárta, B. Turek, J. Bártová, M. Langová, M. Anděl
Czech J. Food Sci., 2002, 20(5):181-191 | DOI: 10.17221/3530-CJFS
Using the Ames bacterial mutagenicity test and an in vivo micronucleus test, we investigated the antigenotoxic effect of ellagic acid on the genotoxicity of three mutagens: amino-methylimidazo-quinoline (IQ), aflatoxin B1 (AFB1), and N-nitroso-N-methylurea (MNU). Ellagic acid is a naturally occurring phenolic compound which is found in a variety of soft fruits and vegetables. The effect of this compound on the immunosuppressive activity of mutagens was followed in vivo by the chemiluminescence test. In the Ames assay, ellagic acid at concentrations of 300 and 30 μg/plate demonstrably inhibits the mutagenic activity...
Residence time distribution during egg yolk pasteurisation
A. Landfeld, R. Žitný, M. Houška, K. Kýhos, P. Novotná
Czech J. Food Sci., 2002, 20(5):193-201 | DOI: 10.17221/3531-CJFS
This work describes the determination of the average residence times during egg yolk - and whole liquid eggs pasteurisation in an industrial pasteurisation equipment (plate pasteuriser + tube holder). For the detection of the impulse the conductivity method was used. Conductivity was then monitored using the bridge method. In the system, the total of 3 probes were placed. To mark the particles of the flowing product, salted yolk with the content of salt of 1.3 or 1.8% was used. In addition, rheological properties of pasteurised yolk were determined at the temperatures of 5, 25, 45, and 65°C. Based on the geometry of the channels in the individual sections...
Testing of scanner and colour-meter for observation of changes during storage of two selected foods
P. Novotná, K. Kýhos, A. Landfeld, J. Strohalm, M. Houška
Czech J. Food Sci., 2002, 20(5):203-208 | DOI: 10.17221/3532-CJFS
The test with colour and aroma of Kladno cooked pork loin stored in refrigerator and at the room temperature correspond with its spoilage was done. No change of the L* co-ordinate has been observed during the storage. A strong decrease of a* co-ordinate for red colour after 1-day storage has taken place for samples stored in a room (approx. 25°C). Conversely, an increase of b* coordinate for yellow colour has been observed after 1-day storage. A change of the cooked pork loin aroma has also been noticed after 1-day storage using the sensory observation. Further, the possibility has been tested of using a portable scanner for the determination of banana...