Shawky M. Dagher

Solubility of Cod Muscle Myofibrillar Proteins at Alkaline pH

Abstract The solubility characteristics of proteins are of interest because of their relation to many functional properties. The solubility of the proteins of washed cod muscle mince increased dramatically between pH 8.9 and 9.2 at an ionic strength of 10 mM, whereas a high but constant solubility was observed at 430 mM sodium chloride over the pH range from 7 to 9.5. At pH 9.2, the proteins of the washed cod muscle were greater than 60% soluble at a sodium chloride concentration of 6.6 mM but were salted out at slightly higher concentrations. Above about 100 mM to about 900 mM salt, the proteins were salted in, and greater than 90% solubility was achieved. Maximal extractability was observed with a ratio of 36 volumes of extracting solution to 1 weight of minced muscle at pH 9.2. At pH 8.5, the extractability of the protein increased from 11% to 24% over a range in extraction volumes of 12:1 to 144:1 of volume of extracting solution to muscle tissue weight.

DDT residues in Lebanese soils.

Abstract The present study was conducted to evaluate the levels of residual DDT in Lebanese soils. A total of 113 surface soil samples were collected for analysis from three major agricultural regions in the country: Mount Lebanon, Beqa’a valley and the coastal plain. The values of residual DDT in soils ranged between 0 and 1190 ng g−1. The majority of the analyzed soil samples were free or contained very low concentrations of DDE. Only two surface soil samples, which were collected from urban areas with high human activities, contained relatively high concentrations of residual DDT. The levels of residual DDT in all of the analyzed soil samples were within the permissible limits for agricultural soils.

Fate of DDT and parathion in grapes processed into arak, an alcoholic beverage.

Arak, the national alcoholic drink in Lebanon, was prepared from grapes to which either DDT or parathion had been added. Samples of the nine fractions produced from the fermentation and distillation steps were analyzed for DDT and parathion and their respective metabolites. DDT degraded to DDD during the fermentation step resulting in a sharp decrease in DDT level. The two distillation steps contributed to a further decrease in the DDT level so that the final product contained less than 2% of the amount found in the fresh grape juice. Although the concentration of DDD increased sharply during fermentation, it also decreased to a negligible level during the subsequent distillation procedure. Parathion was more stable than DDT during the fermentation and first distillation steps. However, the second distillation process caused a sharp decline in its level and the Arak contained only about 6% of the residues present in the fresh juice, paranithophenol being the only metabolite detected.

Comparison of gas chromatography and immunoassay methods in quantifying fenitrothion residues in grape juice processed into alcoholic drinks

Wine and Arak, the national alcoholic drink in Lebanon, were prepared from grape juice fortified with fenitrothion to a concentration of 20ppm. Samples of the 11 fractions produced by the fermentation and distillation steps were analyzed for fenitrothion residues using gas chromatography (GC) and enzyme-linked immunosorbent assay (ELISA). Results of residue analyses showed that the two techniques were highly correlated (r = 0.978) and indicated that fenitrothion was stable during the fermentation steps but not during distillation. The clarified wine 35 days later contained about 85% (15.3 ppm) of the fenitrothion concentration found in the juice as determined by GC analysis. Arak was prepared by a two-steps distillation of the clarified wine. The alcohol distillate and undistilled fraction from the first distillation contained 2.5 ppm and 5.8 ppm of fenitrothion, respectively. No fenitrothion residues were detected by both techniques in the four fractions collected from the second distillation step.

Comparison of Gas Chromatography and Immunoassay Methods for Analysis of Total DDT in Calcareous Soils

Three different calcareous soil samples from Lebanon were analyzed for total DDT pesticide residue using GC and ELISA methods. Two experiments were conducted on three different calcareous soil samples. In each experiment, triplicates of 5 gm soil samples were each fortified with standard solutions of DDE to reach concentrations of 0, 5, 25, 50, 100 and 200 ng g− 1 and allowed to equilibrate at room temperature for 6 hours. Each sample was then extracted with 25 mL of 90% methanol by shaking in glass bottles on a mechanical shaker for 16 hours. The bottles were allowed to stand for 30 minutes and aliquots were taken from the clear supernatant for analyses without further cleanup. The total DDT in the extract was measured in triplicate by GC and ELISA. The results indicated that the two methods were highly correlated (R = 0.955–0.994). Differences in soil properties did not affect the accuracy of the detection limits of ELISA. Immunoassay technique can be used for rapid and accurate measurement of total DDT residues in mineral calcareous soils in Lebanon.

Comparison of gas chromatography and immunoassay methods in measuring the distribution of dieldrin in rainbow trout tissues

Studies have been conducted to determine the distribution of dieldrin in various tissues of rainbow trout when exposed to several dieldrin concentrations. Medium sized fish with an average weight and length of 195.4 ± 30.5 g and 25.7 ± 1.4 cm, respectively, were placed in groups of 6 in 300 L tanks containing purified and aerated water and maintained at 10°C. Following an acclimatization period of 10 days, each group of fish was exposed to one of four dieldrin concentrations ranging from 50 to 80 ppb. After 24 hours, the fish were taken out of the tanks and sacrificed. The brain, gills, liver, muscles and skin were collected from each fish. Dieldrin was extracted from each tissue using SPE techniques and analyzed by both gas chromatography (GC) and enzyme linked immunosorbent assay (ELISA). Results of analyses by the two techniques were highly correlated. The results also showed that liver and skin tissues had the highest level of dieldrin residues. In comparing the means of the six fish samples, it was found that liver or skin contained about 1.5-fold the level in brain, about 4.0 fold the level in muscles and about 6.5 fold the level in gills. Immunoassay proved to be as reliable an analytical tool as gas chromatography in this case.