Incidence of milk leakage after dry-off in European dairy herds, related risk factors, and its role in new intramammary infections.

The incidence of milk leakage (ML) after dry-off (DO) and related risk factors was studied in 1,175 dairy cows from 41 commercial herds in 8 European countries: Belgium, Czech Republic, Denmark, France, Germany, Italy, the Netherlands, and Spain. Milk leakage was assessed twice for 30 s each during 3 visits at 20 to 24 h, 30 to 34 h, and 48 to 52 h after DO. Information related to dry-cow management and udder health was collected at herd and cow level, including individual somatic cell count (ISCC) from test-day controls and occurrence of clinical mastitis cases from DO until 30 d in lactation. Mixed-effect logistic regression analyses were used to identify possible risk factors for ML and to study the association between ML and new intramammary infections. Intramammary infections were defined as clinical mastitis cases during the dry period and in the first 30 d in lactation or a rise in ISCC from before to after the dry period (threshold: 200,000 cells/mL) or both. Milk leakage was observed in 24.5% of the cows between 20 and 52 h after DO, where the herd incidence varied between 0.0 and 77.8%. The reduction in number of milkings in the weeks before DO had statistically significant effect on the ML incidence. When the milking frequency was reduced from 3 times/d to 2 or maintained at twice a day, cows had 11 (95% CI = 3.43-35.46) or 9 (95% CI = 1.85-48.22) times higher odds of leaking milk, respectively, compared with cows where the milking frequency was reduced from twice to once a day. Also, the milk production 24 h before DO was associated with ML incidence. Hence, cows with a milk production between 13 and 21 L or above 21 L had 2.3 (95% CI = 1.48-3.53) and 3.1 (95% CI = 1.79-5.3) times higher odds of leaking milk, respectively, compared with cows with a milk production below 13 L. A higher ML incidence was present in the group of cows with an average ISCC in the last 3 mo before DO ≥200,000 cells/mL (odds ratio = 1.7; 95% CI = 1.13-2.41) compared with cows with an average ISCC <100,000 cells/mL. Quarters with ML tended to have 2.0 times higher odds of developing clinical mastitis compared with quarters not leaking milk. Cows with ML tended to have 1.5 times higher odds of intramammary infections (i.e., an increase of ISCC or clinical mastitis) compared with cows without ML.

Determination of aryloxyphenoxypropanoic acid derivatives in crops treated with herbicidal sprays.

A reproducible and sensitive gas chromatographic method has been developed for the trace analysis of fluazifop-butyl, haloxyfop-ethoxyethyl and quizalofop-ethyl as well as their main metabolites (corresponding acids analysed after conversion to methyl esters) in some fruits and vegetables treated with herbicidal sprays. Comparable detection limits (0.01 mg/kg) were achieved when mass fragmentography and/or the electron capture detector were employed. However, in the latter case, bromination of fluazifop esters had to be carried out prior to GC analysis. By means of the nitrogen-phosphorus detector, determination of residues at a level of 0.05 mg/kg was possible. The residue values found in strawberries, cabbages, cauliflower and carrots were used to discuss the degree of metabolic hydrolysis of parent esters, i.e. active ingredients of herbicides.

Interactions of oxidized lipids with protein. Part XVI. Interactions of oxidized ethyl linoleate with collagen.

The reaction of ethyl linoleate with collagen proceeded at 60 degrees C following the first order kinetics but during the hydroperoxide decomposition the rate constant of the first order decomposition was substantially lower than that of the second order decomposition. Contrary to cellulose, collagen catalyzed the hydroperoxide decomposition. The amount of total oxidation products rose rapidly at the stage of rapid hydroperoxide formation, and slowly afterwards. The browning reaction was fasted in the stage of maximum hydroperoxide content, and both ether-insoluble and ether-soluble pigments were formed, the latter low in nitrogen. The amount of lipid oligomers increased mainly in the reaction stage following the hydroperoxide maximum. Soluble collagen was converted into insoluble forms by the reaction with oxidized lipids. Basic amino acids were blocked by reaction with oxidized lipids but the bonds formed became resistant to acid hydrolysis only in the stage following the hydroperoxide maximum. Changes of sensory profiles could be explained by reactions of flavour-active carbonylic oxidation products with protein.

Gas chromatographic determination of diquat and paraquat in crops.

A sensitive and reproducible gas chromatographic procedure for the determination of diquat and paraquat in potatoes and rapeseed was developed. The volatilization of analytes was carried out via their hydrogenation with sodium borohydride-nickel(II) chloride. After their isolation from the reaction mixture, the derivatives of bipiperidine were separated on a column packed with Apiezon L plus potassium hydroxide. Comparable detection limits (0.005 mg/kg) were achieved with a nitrogen-phosphorus detector and by mass fragmentography, however, the latter method was preferred for analyses of rapeseed extracts owing to its higher selectivity.

Gas chromatographic determination of chlorinated phenols in the form of various derivatives.

Derivatization of chlorophenols prior to gas chromatographic analysis resulted in a significant improvement of their chromatographic behaviour. Chlorophenols in the form of anisoles, acetates, and pentafluorobenzyl ethers were separated either on a HP-1 wide-bore capillary column or on a capillary column coated with a film of SE-54. Due to an enhancement of the poor electron-capture detection response of mono- and dichlorophenols, pentafluorobenzylation made it possible to determine trace amounts in spiked water. Moreover, simultaneous analysis of phenoxyalkanoic acids was accomplished under the same conditions.

Gas chromatographic-mass spectrometric investigation of phenoxypropanoic acid derivatives possessing herbicidal activity.

Fluazifop-butyl, haloxyfop-ethoxyethyl and quizalofop-ethyl, active ingredients of new selective herbicidal preparations, as well as their metabolites converted in to corresponding methyl esters were separated on several gas chromatographic columns. Bromination of fluazifop esters increased significantly the response of the electron-capture detector. Electron impact mass spectra of all the compounds investigated were recorded, and characteristic ions suitable for selected ion monitoring are given.

Residues of clopyralide (3,6-dichloropicolinic acid) in strawberries and their changes.

Residues of clopyralide in strawberries treated with herbicide preparation Lontrel 300 were determined using gas chromatographic method. The decrease of clopyralide content during the processing of contaminated fruits was observed. The rate of decomposition of this compound in model solutions (held at 75 degrees C, pH 3.6) followed first-order kinetics. 2,5-dicloropyridine was proved to originate under these conditions from parent compound.

Reactions of oxidized lipids with protein. Part 15. Mechanism of lipoprotein formation from interactions of oxidized ethyl linoleate with egg albumin.

During the reaction of oxidized ethyl linoleate with egg albumin in dry medium at 60 degrees C, hydroperoxides were rapidly decomposed almost completely, while carbonylic anisidine-active and thiobarbituric-acid-active substances were decomposed rapidly in the beginning and only slowly afterwards. Both hydroperoxides and carbonylic oxidation products were substantially more stable in mixtures with cellulose than with albumin. Hydrogen-bonded lipoproteins were rapidly formed, passed through a maximum, and remained nearly constant in the last reaction stage. Covalently bonded lipids in lipoproteins were mainly formed in the stage following the rapid decomposition of hydroperoxides and carbonylic compounds, and immediately following the decrease of hydrogen-bonded lipoproteins. The binding of oxidized lipids into lipoproteins was accompanied by the formation of protein oligomers and by the loss of available lysine.

Use of gas liquid chromatography/mass spectrometry for triazine herbicide residues analysis in forage and milk.

Residual s-triazines were isolated from forage and milk samples by methanol/chloroform extraction followed by column purification. The evaporated extracts were dissolved in acetone and analysed by gas chromatography with NPD detection and mass spectrometry. The detection limits for both methods were found to be about 5 approximately 10 ng of each s-triazine. The selective ions of the 10 s-triazines investigated (simazine, atrazine, propazine, terbuthylazine, cyanazine, desmetryne, ametryne, prometryne, terbutryne and methoprotryne) were chosen on the basis of an electron impact mass spectrometry study of the s-triazine standards and the whole mass spectra are given. Special attention was paid to the fragmentation of cyanazine and the general cleavage pathways of the s-triazines under investigation.

The fate of ethylenebis(dithiocarbamate) fungicides during processing of contaminated apples.

A spectrophotometric method based on the liberation of carbon disulfide is suitable for the determination of ethylenebis(dithiocarbamate) (EBDC) residues on apples. Homogenization of samples before analysis initiates rapid breakdown of EBDC, resulting in low recoveries. Thermal conversion of mancozeb to ethylenethiourea (ETU) in the course of apple processing was investigated. The formation of ETU from EBDC could be reduced by lowering the pH value. The presence of an antioxidant (ascorbic acid or cysteine) significantly diminished the yields of ETU after heating, but they inhibited its subsequent decomposition. The rate of ETU formation did not correspond to a relatively rapid disappearance of the parent compound. The levels of ETU residues in the canned baby food originating from contaminated apples were evaluated after a 9-months storage period: the reduction of ETU amounts varied from 26 to 70%.

Reactions of oxidized lipids with protein. Part 13. Autoxidation of hexanal in presence of nonlipidic components.

Hexanal is rapidly autoxidized in mixture with nonlipidic substrates even at 25 degrees C. The formation of peroxides follows the kinetics of a first order reaction with respect to hexanal (k1 about 10(-5) min-1), and is higher in mixture with casein or lysine-impregnated cellulose than with cellulose. In mixtures containing pure hexanal, peroxides are decomposed more rapidly after second-order reaction with respect to peroxides (k2 about 10(-3) mmol X kg-1 X min-1) while only slowly by the first-order reaction (k3 about 10(-5) min-1). In presence of small amounts of hexanoic acid the rate of second-order peroxide decomposition remained unaffected while the rate of the first-order peroxide decomposition increased by 4 orders (k3 about 10(-1) min-1). The presence of peroxides was percepted in the odour by sensory analysis contrary to nonvolatile lipid hydroperoxides.

Modified determination of 2-thiobarbituric acid value in fats and oils.

Several methods for the determination of TBA-value were compared with a new direct modification (omitting the previous distillation), using 1-butanol as the sole solvent. The absorbance is measured at 530 nm after heating to 95 degrees C for 120 min, and cooling. The effect of variables was tested by the Youdens ruggedness test (reaction time, temperature, cooling, concentration of sample, thiobarbituric acid, water, heavy metals, antioxidants, chelating agents, bubbling with oxygen or nitrogen). The Lambert-Beers law is valid in the absorbance range between 0.05 and 0.8. The repeatability is better than that of the Dzikowskis procedure and comparable with those of more complicated distillation methods. The standard deviation is in a linear relation with the absorbance (range 0.1-1.0). The method was found satisfactory for evaluating lard, cooking fat, soybean, sunflower, and rapeseed oils in the stage of beginning rancidity.

Mutagenicity of glycerol chlorohydrines and of their esters with higher fatty acids present in protein hydrolysates.

3-chloro-1,2-propanediol and 1,3-dichloro-2-propanol caused base substitutions in Salmonella typhimurium TA1535 both with and without metabolic activation. Metabolic activation seemed to act mainly by decreasing the toxicity of these compounds. A difference in the growth of the wild-type and repair-deficient strains of Escherichia coli was observed only for 1,3-dichloro-2-propanol with S9 mix. Esters of both chlorohydrines with fatty acids has smaller mutagenic effects than unesterified compounds.

The stability of dichlofluanid and vinclozolin and their influence on the quality of strawberries.

The content of dichlofluanid and vinclozolin found on strawberries treated with Euoparen and/or Ronilan, respectively, did not exceed the residue tolerance. Further decrease of the amount of these fungicides occurred during heatsterilisation of the fruit and storage of the products. The rate of decomposition of dichlofluanid and/or vincolozolin in model solutions (pH 3.0-6.0) followed pseudo-first-order kinetics. The taste and flavour of untreated fruit was preferred to those of strawberries treated with fungicides. There were differences in the content of reducing sugars, volatile fatty acids and titrable acidity in individual samples. Gas-chromatographic profiles of volatile substances isolated from treated and untreated berries also differed.

Persistence of fungicide Euparen on strawberry and/or in some canned products of strawberry.

There was studied the persistence of Euparen(dichlofluanid) on strawberry and in some canned products of strawberry, respectively. The rate of decrease of dichlofluanid residues on the leaves of strawberry is proceeding according to the first-order reaction kinetics in the initial 21 days. The content of dichlofluanid residues on strawberry treated twice with fungicide varies from 0.5 to 1.0 ppm, for strawberry sprayed three times from 1.0 to 2.0 ppm, respectively. The significant decay of dichlofluanid residues occurs during the technological procedures applied. The sensoric analysis of strawberry has proved the negative influence of the third spray of fungicide in the initial days. No significance differences between strawberry treated with fungicide and control has been found in flavor and taste of the canned products investigated.

Chlorohydrins in protein hydrolysates.

Four samples of neutral fractions of protein hydrolysates were separated by gas chromatography and the individual components were identified from the mass spectra obtained. Some of the identified compounds were not previously reported as volatile components of foodstuffs. Three of these compounds namely 3-chloropropan-1-ol, 2,3-dichloropropan-1-ol, and 1,3-dichloropropan-2-ol, were toxic chlorohydrins. 1,3-Dichloropropan-2-ol was present in samples in concentrations 0.17 to 0.94 mg/kg. To check the possibilities of the formation of these chlorohydrins and to find their precursor, glycerol, and hydrochloric acid mixtures were heated under conditions of producing protein hydrolysates. All three chlorohydrins, formerly found in protein hydrolysates have been identified.