Search Results

You are looking at 171 - 180 of 497 items for :

  • "concentration" x
  • Materials and Applied Sciences x
  • Architecture and Architectonics x
  • All content x
Clear All

The influence of three milling techniques (MT1: industrial roller-grinder, MT2: grain hammer crasher, and MT3: traditional millstone) and two baking methods (BM1: industrial oven, BM2: traditional ceramic stove heated by wood (log fire oven)) on mycotoxin deoxynivalenol (DON) and nivalenol (NIV) levels in bread were investigated. The DON and NIV concentrations in wheat grain, flour, and bread were analysed using high performance liquid chromatography with UV-detection methods. The 2 500 kg lot of wheat grain containing 1 400–1 900 μg kg −1 deoxynivalenol and 130–200 μg kg −1 nivalenol was divided into sub-lots which were processed to get three types of flour (F1: industrial bread flour, F2: industrial wholegrain flour and F3: traditional wholegrain flour). The concentrations of DON and NIV measured after milling the grain according to MT1 (yielding F1) amounted to 310–370 \g kg −1 and <50–70 μg kg t1 , respectively. After applying MT2 to the grain (yielding F2), the DON and NIV levels were measured to be 1 060–1 400 μg kg −1 and 60–87 μg kg −1 , respectively. Applying MT3 (yielding F3) produced a DON level of 1 100–1 770 μg kg 1 and a NIV level of 80–95 μg kg −1 . Six types of bread were baked from the three types of flour according to BM1 or BM2, and the mycotoxin levels were analysed. The average reduction in DON concentration after baking (70 min at 195–235 °C) was 47.2% for bread baked in the industrial oven and 48.7% for bread baked in the log fire oven. Concentrations of DON in bread prepared by the industrial MT1 were under the permitted limit of 500 μg kg −1 stated in EC (2006) regulation, despite the fact that the bread was baked from grains highly contaminated with mycotoxins. In the bread baked from traditional wholegrain flour, mycotoxin concentrations were higher (850–950 μg kg −1 ).

Restricted access

characteristics, dissolved oxygen concentration, biomass amount). It has a long tradition to use Activated Sludge Models (ASM) model family [ 10 ], therefore a lot of experience is gained in model calibration and validation procedure. These models focus on

Open access

Competition between a bacteriocinogenic and a non-bacteriocinogenic Lactococcus lactis strain, respectively, and a Listeria monocytogenes strain was studied in two semi-synthetic liquid media at various temperatures. The media used for the study were ST I and modified ST I broth (ST I broth + 1 g l-1 Tween 80). In both media, at 30 °C, a significant cell count reduction (5 log) of L. monocytogenes occurred only when the cell concentration of the bacteriocinogenic competitor reached the level of at least 107 CFU ml-1 required for the production of sufficient concentration of nisin-like bacteriocin. The same phenomenon was also observed when the initial level of the lactic acid bacteria (LAB) was one log higher or lower than that of the Listeria, however, the reduction of Listeria cell count occurred earlier with the higher initial concentration of the LAB. Incubation of the mixed cultures at 20 °C gave similar results but the bacteriocinogenic activity resulted in only a three log decline of the cell count of L. monocytogenes. At 10 °C Lactococcus lactis produced much less bacteriocin than at 30 °C, therefore, a drastic decrease of the Listeria cell count was not observed. Suppression of the Listeria growth was expressed in its decreased maximum population level (i.e. in an earlier appearance of the stationary phase). When the non-bacteriocinogenic Lac. lactis and Listeria were present at the same initial level (approx. 105 CFU ml-1), the Lactococcus did not affect the growth of L. monocytogenes at 30 °C in modified ST I broth.

Restricted access

The abandoned Smolnik mine is regarded as an environmental loading in the Central Europe region, where acid mine drainage (AMD) is generated and discharged from abandoned mine and contaminates the Smolnik creek catchments. The whole mine complex produces large amounts of AMD with the pH 3–4 that contain high metal concentrations, fluctuating depending on rainfall intensity.The main aim of this work is to compare and to interpret the method of adsorption for the heavy metals (Cu, Fe, Al, Mn and Zn) removal from AMD out-flowing from the shaft Pech of the deposit Smolnik (Slovak Republic).

Restricted access

The paper presents the results of leachability testing of selected heavy metals from the concrete composites of various compositions in order to assess the degree of a contamination risk of the environment. Tested concrete samples contained various amounts of special ingredients based on the blast furnace slag (65%, 75%, 85% and 95% of Portland cement replacement). Leaching tests have been performed by using distilled water. The concentrations of chromium and barium ions in the leachates were measured after period of 30 and 240 days. Changes in pH and conductivity values in leachates have been also observed.

Restricted access

Unsuitable feed water quality causes fouling and serious decrease in membrane permeability during the operation of reverse osmosis filters, which leads to costly operation and low contaminant removal efficiency. The purpose of the experiment was to create a detailed, yet simple calculation scheme, suitable for higher education and everyday pilot experiments. The obtained formulas were calibrated against measured results, while investigating the fouling of the membranes at different iron concentrations. Pressure losses on a reverse osmosis equipment with a permeate capacity of 100 L/h were investigated for almost a year. Changes in permeability and cleaning methods were investigated with different feed water qualities.

Restricted access

Lactic acid bacteria were isolated from tungrymbai, a traditional fermented soybean product of Meghalaya, India and assessed for their probiotic properties. Survival under simulated gastric conditions was tested and five acid tolerant strains were selected. By using 16S rDNA sequencing, these isolates were confirmed to be Enterococcus species. The strains exhibited good survivability in high concentrations of bile salts. The strains were susceptible to antibiotics and they were also found to inhibit growth of Staphylococcus aureus and Escherichia coli. The strains were gelatinase negative and non-haemolytic. The strains also assimilated cholesterol up to a certain level. The study confirmed that all identified five strains have in vitro probiotic properties.

Restricted access

Even if plants can contain high levels of nitrate and nitrite, milk and dairy products are not described as sources of these anions. The purpose of this paper was to measure the concentrations of nitrate and nitrite in forage, cow blood, and milk.The results show that the nitrate ratio of milk to plasma is very low, suggesting that milk contamination with nitrate is unlikely to occur. This finding also proves the lack of an active transport mechanism to transfer nitrate from blood to milk. The nitrite anion almost disappears from milk through an enzymatic conversion; usually levels of μg l−1 were measured.

Restricted access

Pollution of the natural environment by heavy metals is a universal problem because these metals are indestructible and most of them have toxic effects on living organisms, when permissible concentration levels are exceeded. The degree of contamination in the sediments of the Smolnik creek, for the metals Ca, Mg, Fe, Mn, Al, Cu, Zn, As, Cd and Pb, has been evaluated using Enrichment factor (EF), Pollution load index (PLI) and Geo-accumulation index (Igeo). The sediments have been found to be contaminated with Pb, Cu and As which has been attributed mainly acid mine drainage from abandoned shaft Pech (the mine Smolnik) since no major industrial establishments are present in the area.

Restricted access

For open channels significant pollution sources during the intensive precipitations are outflows from storm-water overflows on the sewer network. When combined with low discharges in rivers, the water released from overflows can cause high concentration of pollution in receiving open channels. In this paper, the results of computer modeling of the impact of storm-water overflows on the stream water quality in three municipalities in Czech Republic are shown. The local river networks are the main receivers in the cities where storm-water overflows are led in. The results serve as a base for the proposals on the measures, improvements and structural modifications.

Restricted access