• Analytical Science and Technology
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• v.16 no.4
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• pp.325-332
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• 2003

To analyze co-planar PCBs in food, the isotopic dilution method by high resolution gas chromatography/high resolution mass spectrometry was applied. Among 209 PCB congeners, 12 congeners (#77, #81, #126, #169, #105, #114, #118, #123, #156, #157, #167 and #189) were chosen as target compounds that were toxic congeners re-assessed by WHO in 1998. Milk and milk products including cheese and butter were collected as food samples. Samples were homogenized, spiked with the known amount of the standard mixture and extracted. After extraction, extracts were cleaned up by sulfuric acid impregnated silica gel, purified on silica gel and alumina column chromatography and then analyzed by HRGC/HRMS. As results, the overall recoveries were ranged from 83% to 106% and the limit of detection was about 0.1 pg/g at signal/noise>3. Levels of targets in the selected food samples were 0.001~0.107 pgWHO-TEQ/g.

• Journal of Korean Society on Water Environment
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• v.32 no.6
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• pp.628-648
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• 2016

Increased attention has been paid to the presence of veterinary antibiotics in various environmental matrices due to their toxicological behavior in the ecosystem and development of antibiotic-resistant strains of pathogenic bacteria. In the this review, 37 target antimicrobials were selected based on annual sales of antibiotics for livestock in South Korea 2014. Also, extraction and clean-up methods for the determination of the antibiotic residues in liquid samples including water, milk, and honey were comprehensively reviewed in the literature. Solid-phase extraction (SPE) was commonly used as a pre-treatment method for the samples. Most of the analytes were extracted in acidic conditions (2.5~4.0) except for aminoglycosides, which were extracted in neutral conditions (7.0~8.0). ${\beta}-Lactams$ showed the highest recoveries in neutral pH due to their degradation characteristics in acidic media. Starta-X, Oasis HLB, and Oasis MCX were frequently applied as an SPE cartridge and Oasis HLB showed the highest recoveries for the majority of antibiotic classes. The homogenized honey and milk were extracted by mixing with acids for deproteinization. Solids and other interfering substances in the extract were eliminated by centrifugation followed by membrane filtration or SPE before injection into HPLC.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.2
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• pp.267-276
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• 2005

This study was carried out to investigate the effect of phytosterol ester addition on lowering blood cholesterol in cholesterol-reduced Cheddar cheese. For cholesterol removal, separated cream was treated with 10% ${\beta}$-cyclodextrin at 800 rpm, then blended with remaining skim milk and homogenized with 1,000 psi at $70^{\circ}C$. Experimental cheeses were manufactured by five different levels of phytosterol addition. After the cholesterol reduction process by ;${\beta}$-cyclodextrin, the cholesterol removal rate was in the range of 91.0 to 92.1%. Amount of short-chain free fatty acid and free amino acids increased with an increase of phytosterol ester, and those were significantly different from that of control in all ripening periods. All rheological properties also increased with an increase of phytosterol ester during ripening period. In sensory analysis, the scores of rancid, bitterness Cheddar flavor and off-flavor intensities increased significantly, while texture was decreased during ripening in phytosterol ester-added groups. Total blood cholesterol was reduced by 18% when rats were fed Cheddar cheese treated with 8% phytosterol. The present study indicated that phytosterol ester addition resulted in a profound lowering effect of blood with cholesterol-reduced Cheddar cheese.