共查询到20条相似文献,搜索用时 0 毫秒
1.
The mycotoxin deoxynivalenol (DON) is one of a group of mycotoxins known as type B trichothecenes and is particularly formed
by the mould speciesFusarium graminearum andFusarium culmorum. The frequency of the occurrence of DON in certain raw materials and the concentrations found make it one of the world’s
most significant mycotoxin contaminants. Positive findings of the toxin especially have been established in cereal-based foods,
as well as in oilseeds.
The main objective of this study was to set up a current situation assessment of the possible occurrence of deoxynivalenol
in cocoa and cocoa products. As there was no analytical method for determining DON in cocoa and cocoa products, a special
method was developed. The applicability and consistency of the method was confirmed by performing recovery assays on various
cocoa products. A special post-column derivatisation procedure was developed to increase selectivity and raise sensitivity
by a factor of 80.
The method was used to test 230 samples for possible DON content, ranging from cocoa beans to cocoa bean shells, nibs, cocoa
liquor and cocoa powders through to finished cocoa-based products. The results suggest that DON may occasionally occur in
cocoa beans in very low concentrations.
Presented at the 29th Mykotoxin-Workshop, Fellbach, Germany, May 14–16, 2007 相似文献
2.
3.
4.
A new simple and sensitive spectrophotometric method is suggested for determining the catecholase activity of diphenoloxidase. The method is based on the enzymatic oxidation of pyrocatechol to 1,2-benzoquinone (BQ) in the presence of the excess of ethylenediamine sulphate (EDA). The condensation product (products) of BQ and EDA (P365) is stable in the solution and possesses strong absorption in the range of 365 nm. The molar absorption factor, E365 (under condition that the molar reaction ratio of catechol to P365 is 1:1) is 15500 M-1 cm-1 on the average. Optimal reaction conditions (pH 7.0, T=25-30 degrees C, [EDA]o = 5 mg/ml) are determined. The advantages and restrictions of the suggested technique in comparison with the methods described earlier are discussed. 相似文献
5.
6.
Peroxidases are very important enzymes, e.g., as preventive antioxidants by removing noxious peroxides from the blood. For this reason we evaluated a colorimetric method which detects the activity of endogenous peroxidases by their reaction with hydrogen peroxide, using tetramethylbenzidine as the chromogenic substrate. This assay design can be easily reversed by change of the variable compound to measure also total peroxides in plasma or serum. An increased total antioxidant status was reported previously by the addition of iodide to human serum. In this study iodide activated the endogenous peroxidases significantly in comparison to control sera and isomolar NaCl as well as horseradish peroxidase. Corresponding to the increased peroxidase activity a concomitant decrease of total peroxides occurred in the same samples. This exchangeable assay design is a beneficial opportunity to screen total peroxide levels as well as peroxidase activity in human sera without time-consuming preparations. The method proved to be simple and is favorable due to its specificity, reproducibility, and low costs. Moreover, we were able to find an explanation for the increased total antioxidant status in the presence of iodide, which is presumably an indirect protective effect via an enhanced activity of enzymatic antioxidants, thereby reducing endogenous peroxides. 相似文献
7.
G Martino M Testa P Vicinanza E Habetswallner 《Bollettino della Società italiana di biologia sperimentale》1978,54(24):2577-2582
Authors describe a new method to determine Mg2+ and Na+K+ATPase activity on extremely small samples of tissue homogenates. They use specific inhibitors to discern between the two activities and a sensitive colorimetric method to dose Pi released from ATP, Lower limit of sensitivity is about 0,0100 micromoles of Pi/mg proteins/hour. 相似文献
8.
9.
10.
11.
Evtugyn GA Eremin SA Shaljamova RP Ismagilova AR Budnikov HC 《Biosensors & bioelectronics》2006,22(1):56-62
Novel immunosensor for nonylphenol (NP) determination has been developed by immobilization of specific antibodies together with horseradish peroxidase on the surface of carbon screen-printed electrode. The signal of the immunosensor is generated by the involvement of NP accumulated in the peroxidase oxidation of mediator (Methylene Blue, hydroquinone or iodide). This results in the increase of the signal recorded by linear-sweep voltammetry. The sensitivity of the detection depends on the nature of mediator, its concentration and incubation period. Cross-selectivity of the response toward readily oxidized phenolic compounds has been determined. The immunosensor developed makes it possible to detect from 20 microgL(-1) to 44 mgL(-1) of NP with detection limit 10 microgL(-1) of NP. 相似文献
12.
13.
The existing method of determining the activity of manganese peroxidase (MnP), produced by Phanerochaete chrysosporium, was improved. 2,6-Dimethoxyphenol at 80 mM was used as a substrate and, after the decolorization of the reaction mixture, H2O2 was added and the initial reaction rate was used to determine MnP activity. 相似文献
14.
15.
16.
Summary The effects of various parameters on Phanerochaete chrysosporium lignin peroxidase activity as obtained in ligninase assay based on the oxidation of veratryl alcohol were investigated. Marked differences in the ligninase activity were observed when the temperature and pH were varied within the ranges of 23 to 37°C and 2.5 to 4.0, respectively, reported to have been used by various research groups. Further, both veratryl alcohol, and hydrogen peroxide concentration had a significant effect on ligninase activity. 相似文献
17.
18.
19.
A sensitive spectrophotometric method for the determination of superoxide dismutase activity in tissue extracts 总被引:12,自引:0,他引:12
Superoxide dismutase (EC 1.15.1.1) has been assayed by a spectrophotometric method based on the inhibition of a superoxide-driven NADH oxidation. The assay consists of a purely chemical reaction sequence which involves EDTA, Mn(II), mercaptoethanol, and molecular oxygen, requiring neither auxiliary enzymes nor sophisticated equipment. The method is very flexible and rapid and is applicable with high sensitivity to the determination of both pure and crude superoxide dismutase preparations. The decrease of the rate of NADH oxidation is a function of enzyme concentration, and saturation levels are attainable. Fifty percent inhibition, corresponding to one unit of the enzyme, is produced by approximately 15 ng of pure superoxide dismutase. Experiments on rat liver cytosol have shown the specificity of the method for superoxide dismutase. Moreover, common cellular components do not interfere with the measurement, except for hemoglobin when present at relatively high concentrations. The assay is performed at physiological pH and is unaffected by catalase. 相似文献
20.
A sensitive fluorimetric method with guaiacol as the hydrogen donor for peroxidase activity is described. The gist of this method is measurement of the fluorescence (excitation, 300 nm; emission, 340 nm) in cyclohexane of mainly a guaiacol dimer which forms in the early phase of the color formation. Optimum conditions of the reaction were compared for horseradish peroxidase and rat thyroid peroxidase preparations. The fluorescence intensity obtained by this method using an enzyme preparation from of a rat thyroid gland correlated well with the color development by the guaiacol method using the same preparation from whole glands of a rat. 相似文献