Gas chromatographic determination of organochlorine pesticides in cow milk

A gas chromatographic method of use in determining the following organochlorine pesticides in cow milk has been adapted and validated: alpha-hexachlorocyclohexane (alpha-HCH), beta-HCH, lindane, delta-HCH, hexachlorobenzene, aldrin, heptachlor, heptachlor epoxide, mirex, 2,4-dichlorodiphenyltrichloroethane (2,4-DDT), 4,4-DDT, 2,4-dichlorodiphenyldichloroethane (2,4-DDD), 4,4-DDD, 2,4-dichlorodiphenylethane (2,4-DDE) and 4,4-DDE. The method studied consists of three steps: the extraction of fat by centrifugation, mixing with anhydrous sodium sulfate, and transfer to a glass column and elution with hexane; purification of the extract via concentrated sulfuric acid treatment; and determination of the organochlorine pesticides by gas chromatography equipped with an electron capture detector. The analytical parameters determined to estimate the quality of the method yielded the following results: correlation coefficients (r) of the calibration curves were greater than 0.996, the variation coefficients of the response factors were less than 4.90%--with the exception of aldrin (5.53%) and lindane (5.75%)--the relative standard deviation of the slope (Sm rel) being < or =1.52%. Zero was included in the confidence limits of the independent term range. The method repeatability and reproducibility values were < or =4.73% and < or =5.79%, respectively. The recovery values of the pesticides analyzed were in the range of 81.92% (alpha-HCH) to 105.49% (4,4-DDT), except in the case of aldrin and heptachlor epoxide, which yielded recovery values of under 40%. The quantification limits of the method were < or =1 ng/g, with the exception of mirex (5 ng/g).

Degradation of polychlorinated biphenyls (PCBs) by Staphylococcus xylosus in liquid media and meat mixture

We investigated the growth of the meat starter Staphylococcus xylosus (10(4) cells mL(-1)) in liquid media containing 0.01 ppm of each polychlorinated biphenyls (PCBs 10, 28, 52, 138, 153, and 180) and its ability to degrade PCBs during 168 h of incubation in liquid media (10(4) cells mL(-1), 0.01 ppm of each PCB congener) and cured meat mixture (0.1% of meat starter, 1 microg g(-1) fat of each PCB congener). PCBs did not affect the growth of the starter microorganism in nutritive (brain heart infusion, BHI) or mineral salts medium (MSM) when compared to control (no PCB). S. xylosus degraded some of the PCB congeners tested. PCBs 138 and 153 were degraded both in BHI (78% and 68%, respectively; p<0.05) and in MSM (71% and 66%, respectively; p<0.05), with maximum degradation being observed within 24 h. Highly significant negative exponential relationships was observed between incubation time and concentrations of PCB 28 and 180 in BHI, as well as for PCBs 52 and 180 in MSM. In the cured meat mixture highly significant negative exponential relationship was observed between incubation time and the concentration of PCB 10. These results indicate that although S. xylosus reduced residues of various PCB congeners in liquid media, it was less effective in cured meat.

Degradation of organochlorine pesticides by meat starter in liquid media and fermented sausage

The effect of meat starter on the degradation of DDT and lindane was investigated. The insignificant role of Lactobacillus plantarum in degrading p,p'-DDT and lindane presented in tryptone soya broth (TSB) and mineral salt medium (MSM) with or without 120 ppm nitrite was observed.The degradation of DDT and lindane by Micrococcus varians in TSB and MSM with or without nitrite were studied. The results indicated that DDT or lindane were degraded during the incubation period. The reduction in DDT at the end of the incubation period (15 days) was about 24.1 and 32.5% in TSB and MSM without nitrite, respectively. Corresponding values in the same media with nitrite were 37.5 and 46.4%. Regarding the reduction in lindane, it was recorded as 27.9 and 40.0% in TSB and MSM without nitrite, respectively and 38.4 and 48.4% in the same media with nitrite. The results indicated that culture media M. varians metabolized DDT mainly to DDD and lindane mainly to 2,4-, 2,5-, 2,6- and 3,4-dichlorophenol; 2,3,4- and 2,3,5-trichlorophenol; hexachlorobenzene; and pentachlorophenol. The effect of pesticides on the growth rate of meat starter was also investigated. The addition of DDT or lindane resulted in a slight decrease in counts of the strains during the initial incubation in TSB or MSM. Then the microorganisms recovered and began to grow logarithmically, but not as well as in a normal situation. The effect of fermentation stage by meat starter on DDT and lindane in fermented sausage was recorded. The results indicated that during the 72 h of fermentation, the reduction was 10 and 18% of DDT and lindane, respectively. These results confirmed that the fermentation process in meat products reduced pesticide residues and these reductions were due to the activity of meat starter.

The effect of commercial processing on incurred residues of DDE in meat products

The influence of processing on the degradation of DDE in meat products was investigated. First, the current level of contamination in six different types of Spanish meat products was determined. Analysis were carried out by capillary gas chromatography with electron capture detector. Of the three residues analysed (both o,p' and p,p' isomers of DDT, DDD, and DDE), only p,p'-DDE was found above the detection limit of 4 micrograms/kg fat. The frequency of p,p'-DDE detection for the various products investigated varied between 78 and 100% of the 129 samples analysed, although mean levels were very low, in the range within 6-16 micrograms/kg. No sample contained DDE residues above the EC maximum residue limit of 1 mg/kg for DDT and metabolites on meat products. Mean concentrations of DDE in Spanish meat products have declined since 1980 by more than 10-fold as compared with previously reported data. Meat products following three commercial processes were analysed to compare the levels of DDE in the finished products with those obtained in the starting material. The average levels of DDE remained unchanged after 30 days of curing in 26 samples of pork sausage. Similarly, mean DDE concentrations were essentially constant throughout the ripening process to which 30 hams were subjected. Finally, cooking in an oven (80-82 degrees C for 100 min) of 20 pork bologna samples produced an apparent increase of 12.5% in mean p,p'-DDE levels that was not statistically significant (p > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)