Czech Journal of Food Sciences, 2000 (vol. 18), issue 3
Non-linear relationship between food resource exploitation and population density of stored-product pestsOriginal Paper
V. Stejskal
Czech J. Food Sci., 2000, 18(3):81-85 | DOI: 10.17221/8315-CJFS 
The main current strategies (IPM, HACCP) to control pests in stored food products are based on critical thresholds derived from pest population density. These thresholds usually do not consider cumulative effects of earlier pest infestation although injuries caused by biotic pest organisms to stored food commodities are irreversible. We present conceptual and illustrative models showing that population size indices, in contrast to cumulative (population history) indices, could (i) underestimate critical thresholds if pest population can grow exponentially and (ii) provide incorrect information about the level of stored food damage if pest population...
Moisture sorption isotherms of millet seedsOriginal Paper
N.D. Menkov, D.I. Gelyazkov
Czech J. Food Sci., 2000, 18(3):86-90 | DOI: 10.17221/8316-CJFS
The equilibrium moisture contents were determined for millet seeds of two cultivars using the gravimetric static method at 10, 25 and 40°C over a range of relative humidities from 0.112 to 0.868. The sorption capacity of the seeds decreased with an increase in temperature at constant relative humidity. The hysteresis effect is not distinctly expressed but statistically significant. The differences between equilibrium moisture contents of the cultivars are small. Four models were applied for analyzing the experimental data using the following equations: modified Chung-Pfost, modified Halsey, modified Oswin, and modified Henderson. The modified Chung-Pfost...
Phenotypic features and enzymatic profile of a Lactococcus lactis strain isolated from wara, an indigenous cheese product from NigeriaOriginal Paper
N.A. Olasupo
Czech J. Food Sci., 2000, 18(3):91-94 | DOI: 10.17221/8317-CJFS
A lactic strain coded NA 1300, isolated from wara, a Nigerian cheese product, was identified as Lactoccus lactis, on the basis of sugar fermentation pattern, and other physiological and biochemical characteristics and by DNA-DNA hybridization. The enzytmatic profile of strain NA 1300 indicated the presence of a wide spectrum of enzymes. The organism exhibited relatively weak esterase and lipase activities as compared with peptidases. The strain showed no proteinase activity. The results are discussed in relation to the role of enzymes in starter selection for cheese production.
Molecular detection of Brucella in milk using polymerase chain reactionOriginal Paper
A. Mohsen
Czech J. Food Sci., 2000, 18(3):95-97 | DOI: 10.17221/8318-CJFS
Brucellosis is a highly contagious disease affecting a wide variety of farm animals. It is also an important zoonosis, and man is often infected following contact with infected animals or the consumption of contaminated milk and milk products. At present, mainly bacteriological and serological detection methods are used. A bacteriological method takes days to weeks to grow the organism besides its health hazard. Serological tests are faster but antigen-antibody interactions can be faulted by non-specific interactions. A method for direct detection of Brucella melitensis in 1 ml of milk was developed on the basis of enzymatic treatment of milk...
Benzoic acid in some milk products from the market in the Czech RepublicOriginal Paper
A. Hejtmánková, J. Dolejšková, V. Horák, H. Dragounová, F. Louda
Czech J. Food Sci., 2000, 18(3):99-102 | DOI: 10.17221/8320-CJFS
Benzoic acid is a natural component of fermented milk products. The level of benzoic acid depends on the level of hippuric acid in used milk and on the process of dairy product manufacture, especially on the technologically used microorganisms. A hygienic limit 30 mg/kg of benzoic acid in milk products was laid down in the Czech Republic in 1997. In our study we determined the levels of benzoic acid in model yoghurts and in some milk products from Czech market. The benzoic acid content was determined by HPLC, by the use of our modification of the provisional IDF standard 139(1987). All samples of model yoghurts and all samples of milk products from...
A new method for rapid detection of Listeria monocytogenes in foodOriginal Paper
K. Zdeňková, K. Demnerová, G. Jeníková, J. Pazlarová
Czech J. Food Sci., 2000, 18(3):103-109 | DOI: 10.17221/8319-CJFS
Listeria monocytogenes represents serious danger for human health. Thus detection of this pathogen in food, which represents its main means of entry into the organism, is a topic of special importance. The original classic methods for the determination of Listeria monocytogenes are in general laborious and time-consuming procedures. In order to address this issue we developed a new rapid method for specific detection of Listeria monocytogenes in food samples. The method consists of three steps: i) enrichment of food microflora (16 h), ii) selective isolation of Listeria sp. exploiting immunomagnetic separation (2-3...
Influence of the specific growth rate on formation of sterols in yeast Saccharomyces cerevisiae during fed-batch cultivationOriginal Paper
J. Čermák, M. Rychtera, P. Nechvíle, J. Náhlík, K. Melzoch, J. Šindelář, J. Vovsík, J. Votruba
Czech J. Food Sci., 2000, 18(3):110-114 | DOI: 10.17221/8321-CJFS
Ergosterol is a major sterol in yeast cells. Intermediates of ergosterol biosynthesis or products of ergosterol biotransformation occur in cells too. Sterols mainly form components of cell membranes. Fluidity of membranes is affected by sterols. The amount of sterols in cells can be influenced above all by cultivation conditions and by the yeast genotype. Specific growth rate is an important factor which affects the amount of sterols present in yeast cells. We carried out a series of 24-hour cultivations to find out the impact of specific growth rate on sterol biosynthesis. Inflow of synthetic medium to the bioreactor was controlled by means of a profile...
Composition and nutritinal value of quinoa (Chenopodium quinoa) - a reviewReview
P. Kalač, J. Moudrý
Czech J. Food Sci., 2000, 18(3):115-119 | DOI: 10.17221/8322-CJFS
Literature data on proteins, lipids, starch, minerals, vitamins and saponins contents and composition and their distribution within whole quinoa seeds, hulls, bran and flour are reviewed. An information on effects of quinoa processing on nutritional value and food applications is also given.