Mestdagh FJ  De Meulenaer B  Van Poucke C  Detavernier C  Cromphout C  Van Peteghem C 《Journal of agricultural and food chemistry》2005,53(15):6170-6174

Acrylamide formation was studied by use of a new heating methodology, based on a closed stainless steel tubular reactor. Different artificial potato powder mixtures were homogenized and subsequently heated in the reactor. This procedure was first tested for its repeatability. By use of this experimental setup, it was possible to study the acrylamide formation mechanism in the different mixtures, eliminating some variable physical and chemical factors during the frying process, such as heat flux and water evaporation from and oil ingress into the food. As a first application of this optimized heating concept, the influence on acrylamide formation of the type of deep-frying oil was investigated. The results obtained from the experiments with the tubular reactor were compared with standardized French fry preparation tests. In both cases, no significant difference in acrylamide formation could be found between the various heating oils applied. Consequently, the origin of the deep-frying vegetable oils did not seem to affect the acrylamide formation in potatoes during frying. Surprisingly however, when artificial mixtures did not contain vegetable oil, significantly lower concentrations of acrylamide were detected, compared to oil-containing mixtures.  相似文献   

    

Boekhold  A. E.  Van Der Zee  S. E. A. T. M.  De Haan  F. A. M. 《Water, air, and soil pollution》1991,(1):479-488

To investigate Cd behavior in a heterogeneous soil, soil samples were taken along a transect in a field. Total Cd content, Cd concentration in solution, and soil properties controlling Cd sorption were measured. The scale and degree of variability of these parameters were assessed using statistical and spectral analysis. No substantial correlation was found between total Cd and Cd in solution. However, with a scaled sorption model that accounts for effects of pH and organic matter content the variability of total Cd was predicted well as a function of measured concentrations and soil properties. Apparently, total Cd contents of this soil are primarily controlled by the organic matter content and pH.  相似文献   

    

L. Van Laer  F. Degryse  K. Leynen  E. Smolders 《European Journal of Soil Science》2010,61(6):1014-1024

Contaminated riparian soils can release metals to surface water. Periodic waterlogging affects metal mobility but the processes and soil factors governing net trends are not well understood. Experiments were combined with geochemical modelling to identify processes explaining the dynamics of zinc (Zn) in contaminated soils following waterlogging. Samples were collected from 12 Spodosols near streams in a metal‐contaminated area and four similar but uncontaminated soils were sampled in a reference area. Air‐dried samples were submerged and incubated under N₂. The soil redox potential decreased from 470 mV initially to approximately 30 mV over 2 months. The pore‐water Zn concentrations surprisingly increased over the same period by, on average, a factor of 18 (range 0.6–80; immobilization in one soil only) despite an increase in pH of 1.8 units, on average. Dissolved organic matter (DOM) in the soil solution increased during waterlogging but the observed increase in Zn solubility could not be explained by increased complexation with DOM, because the estimated Zn²⁺ activity also increased by a factor of 18 on average (range 0.2–82). Speciation modelling suggests that Zn mobilization during waterlogging results from Fe²⁺ displacing sorbed Zn²⁺ from particulate organic matter and from dissolution of Zn‐bearing Fe/Mn oxyhydroxides. This hypothesis is supported by the significant positive correlation (r = 0.87, n = 13) between the factor change in pore‐water Zn concentration and the ratio of dithionite‐extractable Fe to organic carbon content. These results show that Fe dynamics are important for predicting the fate of trace metals in anoxic soils.  相似文献   

    

S. J. Symons  G. Venora  L. Van Schepdael  M. A. Shahin 《Cereal Chemistry》2009,86(2):164-169

An objective imaging method was developed to count dark specks in spaghetti. The method simultaneously measured individual speck size and color and the overall color of the spaghetti. Spaghetti samples were prepared from durum wheat samples collected from the Prairie Registration Recommending Committee for Grains (PRRCG) durum wheat cooperative trials during four consecutive crop years from 2002 inclusive to 2005. Differences in speck counts were found between samples within each year. From year to year, the baseline for speck counts varied with the highest numbers in 2005 and the lowest numbers in 2004. For comparison, three technicians also counted the number of specks in each sample. These visual counts were not consistent between technicians or technician to the imaging method, supporting the need for this objective approach. Spaghetti speck counts did not relate to the speck counts of the semolina subsequently used to prepare the product. Speck sizes were consistent across samples and between years, indicating a consistent milling method for all the samples. Differences in speck count numbers could not be attributed to differences in speck color or pasta color. The imaging method gave very consistent speck counts and color measurements over the four years.  相似文献   

    

Van der Plancken I  Van Loey A  Hendrickx M 《Journal of agricultural and food chemistry》2007,55(1):127-135

This article addresses the effect of moisture content (0.8-9.9%) during dry-heating (80 degrees C) on selected physicochemical (solubility, turbidity, residual denaturation enthalpy, aggregation, surface hydrophobicity, and sulfhydryl content) and functional (foaming ability, foam density, and stability) properties of freeze-dried egg white (FDEW). Moisture content during dry-heating proved to be a parameter determining the functionality of the resulting egg white powder. The degree of conformational changes induced in the egg white proteins by dry-heating was strongly dependent on the amount of water present. Preferentially, dry-heating at 80 degrees C should be performed on egg white powder with a moisture content below 6.8%, as the loss of protein solubility above this value is extensive. In addition to insoluble aggregates, soluble, strongly stabilized aggregates were also formed, especially at higher moisture contents. The decrease in denaturation enthalpy, increase in surface hydrophobicity, and exposure of SH groups previously hidden in the protein core and their subsequent oxidation were more pronounced at prolonged dry-heating times and at higher moisture contents. These conformational changes resulted in improved foaming ability and foams with lower density. No effect of dry-heating on the foam stability was observed.  相似文献   

    

J. A. Delcour  I. P. Van Haesendonck  G. Cleemput  D. E. Rogers  R. C. Hoseney 《Cereal Chemistry》1998,75(4):403-407

Rye water-soluble extracts contain a protein fraction that, when added at low concentrations to a straight-dough breadmaking recipe, significantly increased bread volume. Enrichment of the active component is possible by anion-exchange fractionation with diethylaminoethyl-cellulose (DEAE), by ammonium sulfate precipitation, or by using rye bran or shorts milling fractions as the starting material. The active material was not bound to DEAE-cellulose. With ammonium sulfate precipitation, the fractions obtained at 30, 40, and 50% saturation were active in straightdough baking experiments. Iso-electric focusing revealed that fractions active in breadmaking invariably contained alkaline protein fractions (pI > 7.5). Inactivation of enzyme material by boiling the water-soluble extract from rye destroyed all breadmaking activity. The activity of the bread improver was additive to that of potassium bromate but not to that of ascorbic acid. It was not counteracted by catalase, showing that it does not work by a mechanism involving the production of hydrogen peroxide. The extract was not able to overcome the detrimental effect on bread quality resulting from mixing dough in a nitrogen atmosphere.  相似文献   

    

Pablo Inchausti  Henri Weimerskirch 《Biological conservation》2001,100(3):377-386

The Amsterdam albatross (Diomedea amsterdamensis) is one of the rarest bird species of world avifauna, consisting of a single population in the upland plateau of Amsterdam Island (SE Indian Ocean). All breeding birds of the population are today banded and a monitoring program involving mark-recapture procedures has been carried out continuously over the past 16 years. We present the first estimate of risk of decline for the Amsterdam albatross using a stochastic matrix population model, and evaluate the extent to which the measurement errors in demographic estimates may affect the baseline conservation assessment. We also estimate the potential effect that resumption of long-line fisheries in the vicinity of Amsterdam Island (one the alleged causes for its low numbers in the recent past) may have on the persistence of this population. Our results indicate that, in the absence of any impact of long-line fisheries, the Amsterdam albatross is unlikely to experience a decline larger than 20% of the current population abundance over the next 50 years. Our results point out the difficulty to assess with certainty the extinction risk of small populations despite the availability of long term data on their demography. They suggest that a very cautious approach should be taken for the preservation of small populations of long-lived species that cannot sustain any level of incidental by-catch. Any new long-line fishery resuming in the foraging range of the Amsterdam albatross, but especially close to Amsterdam Island, may rapidly put this species at risk of extinction.  相似文献   

    

M. A. A. Paalman  C. H. Van Der Weijden  J. P. G. Loch 《Water, air, and soil pollution》1994,73(1):49-60

Sorption of Cd at low concentrations onto river Rhine suspended matter was examined in terms of sorption rate, reversibility and factors such as competition and complexation with major inorganic sea-water ions. More than 90% of the final amount of Cd is sorbed within the first few hours. Desorption experiments show that the process is virtually reversible. In experiments with diluted sea water the sorption of Cd strongly decreases even at low salinity. Sorption isotherms show that the sorption of Cd in NaNO₃ solutions is regulated by the free Cd²⁺ activity. In a Ca(NO₃)₂ environment the Cd sorption decreases with increasing Ca²⁺ concentrations, which implies competition between Ca²⁺ and Cd²⁺ for the different sorption sites. In different electrolyte solutions of similar ionic strength the sorption of Cd decreases in the solution order NaNO₃ > NaCl > NaCl+MgCl₂+CaCl₂ > diluted sea water. Although inorganic speciation calculations show that even at low salinities dissolved Cd is dominated by Cd-chloro complexes, chloride accounts for only about one third of the increased mobility of Cd. As a result of addition of Ca²⁺ and Mg²⁺ the sorption capacity of suspended matter for Cd is further reduced by a factor three.  相似文献   

  总被引：1，自引：0，他引：1  

S. Van Buggenhout  A. Van Brecht  S. Eren zcan  E. Vranken  W. Van Malcot  D. Berckmans 《Biosystems Engineering》2009,104(2):216-223

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  总被引：1，自引：1，他引：0  

S. De Gryze  H. Bossuyt    J. Six    M. Van Meirvenne  G. Govers  & R. Merckx 《European Journal of Soil Science》2007,58(5):1017-1026

Wind and water erosion induce breakdown of soil aggregates and loss of soil organic matter. Whereas most of the relations between aggregation and its driving factors have been established on a plot scale, these relations might be very different within an undulating landscape where both erosion (by wind or water) and deposition occur. The aim of this study was to investigate to what degree spatial patterns in soil variables influence spatial patterns in aggregation under different tillage intensities. We studied an agricultural field of about 3 ha in the silty region of Belgium. The site was split into a conventional tillage (CT) and a minimum tillage (MT) system. Within the field, 396 geo‐referenced surface soil samples (0–5 cm) were taken and analyzed for organic matter content, quantity of aggregates and a number of other soil properties. Under CT, 28.5% of the total sample variation was explained by the occurrence of depositional areas, 20.8% by the amount of soil organic matter, and 13.8% by the presence of a clay‐rich B horizon which surfaced due to progressive water and tillage erosion. Regression analysis revealed that 27% of the variation in the quantity of macroaggregates (>0.25 mm) was accounted for by these three factors. Under MT, 27.1% of the total sample variation was related to the surface cover of Tertiary sand, 22.6% to the amount of soil organic matter, and 13% to erodibility. These three factors explained 53% of the variation in the quantity of macroaggregates. In the CT system, the correlation between grass‐ or maize‐ carbon and the quantity of macroaggregates was strongly linked to erodibility, while this was not the case in the MT system. We concluded that at this site, macroaggregation is dominated by landscape‐scale processes (such as water or tillage erosion) rather than determined by the commonly considered local variables (such as small variations in texture or organic matter content).  相似文献