Non-lactic acid, contaminating microbial flora in ready-to-eat foods: a potential food-quality index

The bacteriological profile of 87 samples of commercially available ready-to-eat (RTE) dairy and meat-products, packaged sandwiches and salads was obtained by testing for aerobic colony count, for lactic acid bacterial (LAB) count, for the presence and the extent of non-LAB microflora (contaminating microflora), and by testing for certain food-borne pathogens. The pathogens Listeria monocytogenes, Salmonella spp. and sulfite-reducing clostridia were not detected in any of the analysed samples. Whereas only three samples (3.4%) were deemed unacceptable for consumption for exceeding the established pathogen tolerance levels (for Staphylococcus aureus and Escherichia coli), several samples were found to contain non-lactic acid contaminating microflora of considerable magnitude. The log10 cfu g(-1) counts for contaminating microflora in the food categories examined were as follows: hard cheeses 4.85 (SD 1.17); semi-hard cheeses 5.39 (SD 1.37); soft cheeses 5.13 (SD 1.03); whey cheeses 6.55 (1.24); fermented meat-products 4.18 (SD 1.48); heat-treated meat-products 3.47 (SD 1.99); salads 3.37 (SD 1.56) and sandwiches 5.04 (SD 0.96). Approximately 1 in every 30 to 80 bacterial cells found on different types of cheeses and salads was a non-LAB microorganism; the respective ratios for fermented meat-products, heat-treated meat-products and sandwiches were 1 in 6, 2.5 and 15. The assessment of the contaminating microflora magnitude at various steps during the manufacture and distribution of RTE foods can serve as an index for monitoring the microbiological quality of the starting materials, the sanitation efficacy during processing and possible temperature abuse during processing, transportation or storage.     

Implicit modeling using subdivision curves

C ¹ continuity everywhere. Moreover, they can be used to generate representations at different levels of detail, enabling the interactive display of at least a coarse version of the objects, whatever the performance of the workstation. We also present a practical solution to the unwanted-blending problem, used to avoid blending between parts of the surface that do not correspond to neighboring skeletal elements. Published online: 22 May 2003     

Kinetics of Listeria monocytogenes cell reduction in processed cheese during storage

The present work utilized data from a series of challenge tests conducted on a processed cheese product (pH = 5.1, a_w = 0.93) aiming at elucidating whether the processed cheese can support or not the growth of Listeria monocytogenes when stored at 4, 12 or 22 °C (Angelidis, Boutsiouki, & Papageorgiou, 2010). In these challenge tests three L. monocytogenes strains (Scott A, CA and IS951) were used for inoculating samples of processed cheese at three different inoculation levels. Although the results of this previous work have shown that the product did not support the growth of L. monocytogenes at either storage temperature, there were noticeable differences in the inactivation rates of the different L. monocytogenes strains at the different storage temperatures. Therefore, in the present study, the data from the early experiments were used to describe the kinetics of L. monocytogenes cell reduction in processed cheese during storage. A Weibull-type model was initially employed to describe the reduction of L. monocytogenes viable cells as a function of storage time, while the Arrhenius relationship was used to express the effect of temperature on the rate of cell reduction. For each strain, cell reduction data at all temperatures and all inoculum levels were treated as a single data set for the simultaneous determination, through non-linear fitting, of the cell reduction kinetic parameters and their temperature dependence. The proposed approach gave satisfactory results, in terms of agreement between measured and predicted cell reduction, as far as the effect of initial inoculum level and storage time and temperature is concerned. Strain variability was noticeable at the lower temperatures tested, with Scott A being the most resistant among the L. monocytogenes strains examined.     

Mitochondrial Control Region Variability in Mytilus galloprovincialis Populations from the Central-Eastern Mediterranean Sea

The variable domain 1 (VD1) domain of the control region and a small segment of the rrnaL gene of the F mtDNA type were sequenced and analyzed in 174 specimens of Mytilus galloprovincialis. Samples were collected from eight locations in four Central-Eastern (CE) Mediterranean countries (Italy, Croatia, Greece and Turkey). A new primer, specific for the F mtDNA type, was designed for the sequencing procedure. In total 40 different haplotypes were recorded, 24 of which were unique. Aside from the two populations situated in Thermaikos gulf (Northern Aegean, Greece), relatively high levels of haplotype and nucleotide diversity were estimated for both Central and Eastern Mediterranean populations. Eight out of the 40 haplotypes were shared by at least three populations while two of them were found in all populations. Φ_ST and cluster analysis revealed lack of structuring among CE Mediterranean populations with the exception of those located at the Sea of Marmara and Croatian coast which were highly differentiated. Apart from the species’ inherit dispersal ability, anthropogenic activities, such as the repeated translocations of mussel spat, seem to have played an important role in shaping the current genetic population structure of CE M. galloprovincialis mussels.     

Frequency response computation via trigonometric continued fraction

An efficient algorithm for computing the frequency response of discrete-time systems described by rational transfer functions is presented. The algorithm is simple, fast, recursive, and can be used for equally or unequally spaced frequencies. Based on an initial expansion of the system transfer function to a novel Jacobi-type trigonometric continued fraction, the algorithm proposed permits all operations to be performed by real arithmetic, guarantees real results, saves a number of operations, and produces accurate results. The algorithm is easily programmable and needs only 2nN real multiplications/divisions for evaluating the frequency response of an nth-order system at N different frequencies     

Direct phase-domain calculation of transmission line transientsusing two-sided recursions

This paper presents a new method for the simulation of electromagnetic transients on transmission lines. Instead of using convolutions of the input variables only, we perform short convolutions with both input and output variables. The result is a method of two-sided recursions (TSR), which is comparable in efficiency with the existing recursive convolutions or with their equivalent state variable formulations. It is, however, conceptually simpler and can be applied, in addition to fast modal-domain solutions, to the direct phase-domain calculation of transmission line transients with very accurate results     

Management of Upstream Dams and Flood Protection of the Transboundary River Evros/Maritza

The flood frequency and the dikes overtopping at the downstream part of transboundary (Bulgaria–Greece–Turkey) river Evros/Maritza has increased dramatically in the last 13 years. It is not clear if the increase of flood frequency is due to climatic changes or to inappropriate management of Bulgarian dams. This fact raises the question of modeling the flood routing through the many dams in the Bulgarian territory (upstream), which receive the runoff of the 38% of the area of the Evros watershed in Bulgaria, in a way to protect the downstream countries from flooding. The basic objective of this paper is the development of a new management tool (software) for the simulation of the rainfall–runoff and routing process taking into account the existence of many dams and mainly their operation not only from a hydrologic viewpoint, but also from the administrative, with emphasis on the “energy–economic” exploitation of the reservoirs. The developed software (named Evrofloods) models the rainfall–runoff, the routing of runoff through the various Evros river tributaries taking in account various scenarios of the runoff through the artificial reservoirs with the aim of optimal management of the water released from the dams spillways and turbines. The “optimal management” is related with the finding for a given rainfall distribution, the appropriate combination of actions at many reservoirs (“reservoirs management”) in order to prevent or mitigate the floods downstream, aiming at the same time to minimize hydroelectric energy loss. Although Evrofloods software is basically dedicated to the large Evros basin, it can be easily used to determine the management of large transboundary rivers with many artificial reservoirs to avoid floods downstream. Recent European legislation on floods encourages the good cooperation of neighbor countries, to avoid floods.     

Evaluation of the Delvo-X-Press assay for detecting antibiotic residues in milk samples from individual cows.

Performance of the Delvo-X-Press beta-lactam antibiotic assay was examined using bulk-tank milk samples and milk samples from individual cows. Bulk-tank milk samples fortified with bovine lactoferrin at a concentration of 1 mg/ml or more consistently tested positive. False-positive results were also obtained from bulk-tank milk samples fortified with bovine plasma at concentrations of 20 and 40%. The assay yielded positive results for milk with antibiotic concentrations as low as 2 ppb. Individual milk samples were collected from 144 healthy lactating cows and from 34 cows with chronic Staphylococcus aureus mastitis. Specificity estimates for samples from healthy and mastitic cows were 0.88 (95% confidence interval [CI], 0.82, 0.93) and 0.94 (95% CI, 0.86, 1.00), respectively. Individual milk samples were collected from three cows with experimentally induced mastitis for 21 consecutive days. False-positive results occurred as late as 12 days postchallenge. A moderate but significant (P < 0.01) positive linear correlation (r = 0.61) was observed between test result and somatic cell count (SCC) values in milk samples with SCCs of >10(6)/ml.