Influence of smoking parameters on the concentration of polycyclic aromatic hydrocarbons (PAHs) in Danish smoked fish

Abstract

A new method for the analysis of 25 polycyclic aromatic hydrocarbon (PAH) compounds in fish was developed, validated, and used for the quantification of PAHs in 180 industrially smoked fish products. The method included pressurized liquid extraction, gel-permeation chromatography (Bio-beads S-X3), solid-phase extraction (silica gel), and gas chromatography-mass spectrometry analysis. The sum concentration of 25 PAHs (∑PAH₂₅) was highest in smoked herring (n = 3) and mackerel fillets (n = 13), with an average concentration of 320 and 235 µg kg⁻¹, respectively. Lowest average ∑PAH₂₅ concentrations were obtained for indirectly smoked trout (26 µg kg⁻¹). Principal component analysis was used to correlate processing parameters to PAH concentrations and to identify the effects of these parameters. The analysis showed that for salmon hot-smoking conditions lead to higher ΣPAH₂₅ than cold smoking, and for other fish species direct smoking leads to higher ΣPAH₂₅ than indirect smoking. Also, the usage of common alder increases the PAH contamination compared with beech. The effects of smoking time, combustion temperatures, and two types of smoke-generating material on the ∑PAH₂₅ were also tested in a pilot plant study with smoked trout as a model fish. In addition to confirming that increased combustion temperatures and usage of common alder in comparison with beech increased ∑PAH₂₅, it was also revealed that the PAH concentration decreased in the order fish skin ≫ outer layer of the fish muscle > inner part of the fish muscle.

Keywords:

• gas chromatography-mass spectrometry (GC-MS)
• accelerated solvent extraction (ASE)
• clean-up
• EPC
• in-house validation
• polycyclic aromatic hydrocarbon (PAH)
• fish and fish products
• smoked food

Acknowledgements

The authors would like to thank the Danish Ministry of Food, Agriculture and Fisheries for financial support. Project participants from the Danish Seafood Association, the Danish Fish Retailers, the Danish Aquaculture Organisation, the Danish Fish and Export organization, and Knud Fischer are thanked for ideas and cooperation within the project. The authors also thank Carsten Østerberg at DTU Seafood Research for smoking the fish in their pilot plant, Trang Vu at DTU Seafood Research, Anni M. Thomsen, Thomas Dyekjær, and Claus Lorentzen at the Regional Veterinary and Food Administration Center, and Vibeke Balswel at DTU Division of Food Chemistry for chemical analysis. Also, thanks to the food inspectors at the Danish Veterinary and Food Administration and the local smoke houses for collection of the samples and information on processing.