Abstract
A method developed previously for the simultaneous analysis of polychlorinated biphenyls (PCBs), polychlorinated dibenzo- p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in powdered full fat milk is now examined for their determination in yoghurt. The results of this study are consistent with those found for PCBs and PCDD/Fs in powdered full fat milk. The methodology is based on the matrix solid-phase dispersion of the freeze dried yoghurt enabling the extraction of the neutral and apolar lipids of the matrix. Mean recoveries were above 94% for the studied coplanar PCB congeners spiked at the typical reported levels for dairy products and above 92% for the spiked 13 C 12 -PCDD/Fs. The validated methodology was applied to the PCB and PCDD/F analysis in full fat and low fat yoghurts form different brands commercialised in Spain. In all cases, levels detected in the low fat yoghurts analysed were several times higher than those found in the full fat yoghurts when reported on a fat basis (between 3.3 and 11 times for PCBs and between 3.3 and 45 times for PCDD and PCDF homologue groups). In general, this discrepancy applied also for the toxic 2,3,7,8-TCDD equivalents (TEQs) calculated in each case. The calculated TEQs (on a fat weight basis) from PCBs and PCDFs in the low fat yoghurts were higher than those reported previously for different Spanish dairy products, including liquid and powdered milk and butter. Nevertheless, the estimated daily intake (DI) for low fat yoghurts was lower than those calculated for the rest of the dairy products investigated. This apparent contradiction showed that the regulation of PCB and PCDD/F contents should be based on DIs rather than on TEQs reported on a fat-adjusted basis. Finally, the feasibility of differentiation among different dairy products, i.e. liquid and powdered milk, butter and yoghurt, on the basis of their respective PCB and PCDD/F patterns by using multivariate methods, has been shown.
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