Methods of analysis for 2-dodecylcyclobutanone and studies to support its role as a unique marker of food irradiation.

Methods of analysis for 2-dodecylcyclobutanone (2-DCB) using gas chromatography with mass spectrometric detection (GC-MS), liquid chromatography with time-of-flight mass spectrometric detection (LC-TOF-MS) and LC with tandem MS (MS/MS) detection have been developed and optimised for maximum sensitivity to allow very low irradiation doses to be detected. The LC-MS/MS method, following derivatisation with 2,4-dinitrophenylhydrazine, was found to be the most sensitive technique and was used to determine the amount of 2-DCB formed from the model compounds palmitic acid, glyceryl tripalmitate and 1,3-dipalmitoyl-2-oleoylglycerol irradiated over a range of doses by two different irradiation sources (gamma and electron beam). The model compounds were also treated with a number of non-irradiation based processing techniques including heating in the presence and absence of oxygen, light, and redox active metal salts, in a conventional oven, microwave oven and pressure cooker. No 2-DCB was detected in any of the processed non-irradiated model compounds, reaffirming the hypothesis that 2-DCB is a unique radiolytic product that can be used as a marker of irradiation in foodstuffs.

Dietary intake estimate for perfluorooctanesulphonic acid (PFOS) and other perfluorocompounds (PFCs) in UK retail foods following determination using standard addition LC-MS/MS.

The analysis of 252 food samples (UK-produced and imported) purchased from a variety of retail outlets in the UK was undertaken for the presence of perfluorooctanesulphonic acid (PFOS), perfluorooctanoic acid (PFOA) and nine other perfluorocompounds (PFCs). A limit of quantification (LOQ) of 1 microg/kg was achieved for all target analytes, in all samples. Standard addition was used for quantification of PFC levels. All 11 of the targeted PFCs were detected in 75 individual food items. In 70% of the samples, including all meat other than offal, none of the analytes were present above the LOD. The highest levels found were 59 microg/kg perfluorooctanesulphonic acid (PFOS) and 63 microg/kg total PFCs (SigmaPFCs) in an eel sample, and 40 microg/kg PFOS (62 microg/kg SigmaPFCs) in a whitebait sample. The highest level in an offal sample was 10 microg/kg, in a wild roe deer liver. There were six samples with SigmaPFCs >15 microg/kg (fish, shellfish, crustaceans), a further seven samples with SigmaPFCs ranging 11-15 microg/kg (including a liver), nine with SigmaPFCs ranging 6-10 microg/kg (fish and livers), 31 with SigmaPFCs in the range 2-5 microg/kg (including kidneys, popcorn and processed peas) and a further 22 with SigmaPFCs close to the LOD of 1 microg/kg (including eggs and potatoes). These concentrations indicate that UK consumers are being exposed to a low level of PFC contamination from food. The estimated upper bound dietary intake of 10 ng/kg bodyweight (bw)/day of PFOS for average adult consumers is well below the 0.15 microg (150 ng)/kg bw tolerable daily intake (TDI) set by the European Food Safety Authority. The lower bound adult dietary intake estimate of 1 ng/kg bw/day is similar to estimates undertaken and reported in countries such as Canada, Germany and Spain.

Determination of phytoestrogens in dietary supplements by LC-MS/MS.

Labelling data quantifying the exact content of individual phytoestrogen analytes in dietary supplements are generally poor. As these products are commonly used in the management of menopause symptoms, any clinical benefits would be dependent on the exact dosage of isoflavones received. Well-established extraction procedures and updated isotope dilution mass spectrometry liquid chromatography coupled with tandem mass spectrometry detection (LC-MS/MS) have been used to accurately quantify the concentrations of ten common isoflavones in 35 dietary supplement samples on sale in the UK, Canada and Italy. Concentration-specific ionization suppression is described for biochanin A and formononetin. All supplements contained phytoestrogens. The soya isoflavones (genistein, daidzein, glycitein) were present in all products and the majority also contained the red clover isoflavones (biochanin A, formononetin) and some the Kudzu isoflavones (daidzein, puerarin). The content of total isoflavones per dose ranged from <1 to 53 mg. Trace amounts of coumestrol were found in six products. Other less common analytes, the prenylnaringenins (6-prenylnaringenin, 8-prenylnaringenin, 6,8-diprenylnaringenin) were not found in any of the products. Only 14 of 35 supplements were found to deliver more than or equal to 40 mg day(-1) of aglycone isoflavones, a consensus dose value recognized as delivering therapeutic benefit. Eleven did not match label claims. Six delivered less than 10 mg day (-1) of isoflavones. There has been little improvement in the overall quality of industry labelling in the five years since this was last investigated. Consequently, the public, retailers and healthcare professionals should consider using standardized isoflavone supplements, which are supported by analytical measurements.

Dietary exposure estimates of isoflavones from the 1998 UK Total Diet Study.

The phyto-oestrogen contents of the 1998 UK Total Diet Study (TDS) food group composites were determined. Each TDS set consisted of composite samples, one for each of the 20 designated food groups. These composites then represented the average consumption of all the individual food elements in each group, processed into the form in which they were consumed. In the TDS, individual composites of the bread, processed meat and fish food groups contained >5 mg kg(-1) of the individual isoflavones (daidzein, genistein and glycitein). Individual composites from the groups, miscellaneous cereals, other vegetables, fruit products and nuts contained >1 mg kg(-1). After weighting for average consumption of food from each TDS food group, an estimated daily intake of 3 mg day(-1) of combined isoflavone aglycones was obtained from the TDS sample collection model for the average (adult) consumer. The UK dietary intake of phyto-oestrogens is higher than previously estimated due in part to the use of soya in processed foods.

Determination of unusual soya and non-soya phytoestrogen sources in beer, fish products and other foods.

Fish and fish products (14 samples), Indian foods and meals (10 samples), spices (30 samples) and beers (10 samples) were analysed for their phytoestrogen content, and a number of significant non-soya sources of dietary phytoestrogens were identified. No isoflavones were detected in unprocessed, farmed or ocean fish, but some samples of processed fish products contained soya isoflavones, which are assumed to come from coatings or protein addition. Additionally, some processed fish products contained, genistein glycocongugates not derived from soya. Genistein was detected in Indian meals such that, for example, a single portion of a vindalooo curry contained 11 mg genistein. The origin was most likely from the spices used, since the analysis of curry powders, chilli powder, crushed red chillies, garam masala and tandoori powder revealed that some contained genistein at more than 100 mg kg(-1). Cumin was the most likely source material, although not all individual samples of cumin tested contained high levels of genistein. Prenylnaringenin phytoestrogens were determined in UK hop-based beers at mean concentrations of 0.21 mg(-1) 6-prenylnaringenin and 0.06mg(-1) 8-prenylnaringenin. The beers also contained traces of daidzein, genistein and biochanin A. The significance of 'hidden soya' in processed foods and these non-soya sources of phytoestrogens is that UK dietary intake of phytoestrogens must be assumed to be higher than estimated previously and that some sources of phytoestrogens remain poorly characterized.

Verification of the findings of acrylamide in heated foods.

We report here the first confirmation of the recent Swedish findings of acrylamide in heated foods. The verification exercise used an LC-MS/MS method developed for the purpose as well as an established GCMS method for acrylamide analysis. LC-MS/MS was suitable for the direct determination of acrylamide in aqueous extracts of foods by isotope dilution mass spectrometry (IDMS) using triply deuterated acrylamide. Some food matrices were not suited to the new method and mixed-mode solid-phase extraction (SPE) was used to clean these extracts. The foods tested included UK versions of some of the key food groups analysed in Sweden. Also tested were some foods heated under home-cooking conditions. There was good agreement between the LC-MS/MS results and the GC-MS results and the levels of acrylamide found here were similar to those reported for the corresponding foods analysed in the Swedish study. The analyses confirmed that acrylamide is absent from the raw or boiled foods but present at significant levels in fried, grilled, baked and toasted foods. The highest result was 12000 microg kg(-1) acrylamide in overcooked oil-fried chips.