A simple method is described for the determination of cholesterol in milk and milk products. Samples (0.2 g) are saponified in capped tubes with 0.5 M methanolic KOH solution by heating for 15 min at 80 degrees C. Water is added to the mixtures, and the unsaponifiable fractions are extracted with hexane to be further analyzed by capillary gas chromatography. Because of the rapid sample preparation and gas chromatographic procedures, a single sample can be analyzed in 30 min. Overall recovery was 98.6%, and the linearity was excellent for the fortification range examined. Precision data that were based on the variation within and between days suggested an overall relative standard deviation value of 1.4%. The method has been successfully applied to quantitate cholesterol in a variety of milk products.

The effect of the level and form of dietary flaxseed on the fatty acid composition and cholesterol content of hen egg has been investigated. Dietary flaxseed notably altered yolk fatty acid composition by increasing total polyunsaturated fatty acids while decreasing monounsaturated fatty acids. α-Linolenic acid was linearly increased in response to levels of ground flaxseed, but whole flaxseed resulted in reduced α-linolenic acid availability for yolk deposition. Similar deposition profiles were exhibited by docosapentaenoic and docosahexaenoic acids. These alterations in yolk composition resulted in n−6 to n−3 fatty acid ratio values as low as 2.92 and 1.94 for 5 and 10% ground flaxseed and 2.49 for 10% whole flaxseed feeding, respectively. Dietary flaxseed had no effect on the cholesterol level of eggs, which showed a mean value of 188 mg/egg or 1247 mg/100 g of yolk. Keywords: Flaxseed; cholesterol; n−3 fatty acids; yolk; egg

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A simple and rapid methodology for the analysis of fenbendazole residues in cows' milk, at levels down to 3 ng ml-1, has been developed. Samples are extracted with acetonitrile and centrifuged. The supernatant is de-fatted with isooctane, and mixed with dichloromethane. The separated aqueous layer is discarded, while the bottom organic layer is washed with a phosphate buffer (pH 10) and evaporated to dryness. The residue is dissolved in the mobile phase and analysed by ion-pair reversed-phase liquid chromatography, using octanesulfonate as the ion-pair reagent. Over-all recovery was found to be 99.0%, linearity was excellent and precision data based on within- and between-day variation suggested an over-all variation of 2.0%.

The level and nature of the albendazole residues in milk of treated cows were determined as a function of the time of milking (12-h intervals), and the fate of those residues during cheesemaking, ripening, and storage was examined when the obtained milk was used for making Teleme cheese. Ion-pair liquid chromatographic analysis with fluorescence detection showed that the albendazole sulfoxide metabolite reached its maximum (523 +/- 199 micrograms/kg) at the 1st milking and declined below the detection limit by the 4th milking. The sulfone metabolite attained its highest level (812 +/- 99 micrograms/kg) more slowly (at the 2nd milking) and declined below detection limit by the 13th milking. The 2-aminosulfone metabolite, which was present in the milk obtained at the 1st milking, reached its maximum (128 +/- 36 micrograms/kg) at the 3rd milking, and slowly declined to a level below detection limit by the 15th milking. Whey and cheese analysis revealed that about 70% of each major metabolite initially present in milk could be distributed in the whey. The remaining 30% occurred in the cheese at residue levels higher than those initially present in the milk of the 1st or 2nd milking (688 versus 445 or 450 versus 230 micrograms/kg for albendazole sulfoxide; 890 versus 608 or 1502 versus 783 micrograms/kg for albendazole sulfone; 19 versus 15 or 161 versus 105 micrograms/kg for albendazole 2-aminosulfone). Ripening and storage of the cheeses made from milks from the 1st or 2nd milkings results in a decrease of the sulfoxide metabolite (to 225 or 206 micrograms/kg), an increase of the sulfone metabolite (to 1,181 or 1,893 micrograms/kg), and no effect on the 2-aminosulfone metabolite.