Validation of a database on acrylamide for use in epidemiological studies.

BACKGROUND/OBJECTIVES: Acrylamide, a probable human carcinogen, was detected in various heat-treated foods such as French fries and potato crisps. Recently, positive associations have been found between dietary acrylamide intakes, as estimated with a food frequency questionnaire using an acrylamide database, and cancer risk in some epidemiological studies. As acrylamide levels vary considerably within the same type of foods, a validation study was performed to investigate whether use of an acrylamide food database containing calculated mean acrylamide content, based on extensive sampling and chemical analysis of Dutch foods (several samples per food), can classify subjects with respect to true acrylamide intake. SUBJECTS/METHODS: We used the data from a 24-h duplicate diet study. The acrylamide content of 39 Dutch 24-h duplicate diets collected in 2004 was estimated using the mean acrylamide levels of foods available from the database and the menu list, on which the participants of the duplicate diet study had listed the amounts of individual foods and drinks in household units. Next, the acrylamide content of the total duplicate diets was analytically measured and correlated to the estimated acrylamide contents. RESULTS: The Spearman's correlation coefficient between chemically determined acrylamide content and the calculated acrylamide content of the duplicate diets was 0.82 (P<0.001). CONCLUSIONS: This study indicates that it is possible to classify subjects with respect to acrylamide intake if mean instead of actual content of each food is applied. The database can therefore be applied in epidemiological studies on acrylamide intake and cancer risk, such as the Netherlands Cohort Study on Diet and Cancer.

The occurrence of fumonisin B1 in maize-containing foods in The Netherlands.

Seventy-eight maize-containing foods obtained from retail stores in The Netherlands were analysed for fumonisin B1 contamination. Thirty-six per cent of the samples were contaminated with fumonisin B1 in the range of 8 micrograms kg-1 (limit of detection) to 1430 micrograms/kg-1. Forty-six per cent of the minimally treated maize samples (n = 39; maize for bread production, maize for popcorn, maize flour and polenta) were contaminated with fumonisin B1 in the range of 8-380 micrograms kg-1. Twenty-six per cent of the maize-containing processed foods (n = 39; tostada, canned maize, maize starch, maize bread, popped maize, flour mixes, maize chips and cornflakes) were contaminated with fumonisin B1 in the range of 8-1430 micrograms/kg-1. This survey shows that maize-containing foods in The Netherlands frequently can be contaminated with fumonisin B1.

Fumonisin B1 in maize for food production imported in The Netherlands.

Sixty-two samples of maize imported in The Netherlands and intended for human consumption were screened for the presence and concentration of fumonisin B1. Sixty-one of those samples contained fumonisin B1 with concentrations ranging from 30 to 3350 micrograms kg-1, 11 maize samples contained > 1000 micrograms kg-1. The average fumonisin B1 concentration was 640 micrograms kg-1 for the positive samples and 620 micrograms kg-1 for all samples. Medians were 600 micrograms kg-1 and 550 micrograms kg-1 for positive and all samples, respectively. The results obtained were comparable to results from other studies in maize from various countries.

The development of five animal feed reference materials, certified for their aflatoxin B1 content.

The development of three peanut meal and two compound feed reference materials and the certification of their aflatoxin B1 content is described. The materials were prepared and certified within the Measurements and Testing Programme of the Commission of the European Communities as part of a broad activity to improve accuracy and agreement of results of measurements on food and agriculture. RM 262 (peanut meal) was prepared from uncontaminated peanut products. RM 263 and RM 264 (peanut meals) were prepared from naturally contaminated peanuts which were blended with uncontaminated ones, to achieve the desired aflatoxin B1 mass fractions. RM 375 and RM 376 (compound feeds) were made by blending decontaminated dairy feed together with commercial feed ration and contaminated dairy feed with several feed compounds, respectively. Details are given of the preparation and the investigations to verify homogeneity and stability of the materials. The certification exercise was carried out by 17 laboratories using a variety of extraction and clean-up procedures. Most laboratories used liquid chromatography as the determinative step, although operating under a variety of chromatographic conditions. A few laboratories applied thin layer chromatography with densitometric quantification. Peanut meal RM 262 was certified as containing aflatoxin B1 at a mass fraction of < 3 micrograms/kg, RM 263 at 43.3 +/- 2.1 micrograms/kg and RM 264 at 204 +/- 10 micrograms/kg. Compound feed RM 375 was certified as containing aflatoxin B1 at a mass fraction of < 1 micrograms/kg and RM 376 at 9.2 +/- 0.5 micrograms/kg. The materials can be employed either to establish or confirm a calibration curve, or to check the performance of a method.

Two-dimensional chromatographic method for determination of aflatoxins in liver; occurrence of aflatoxins in animal liver.

A thin-layer chromatographic method is described for the analysis of aflatoxins in animal liver. Liver samples are extracted with chloroform and phosphoric acid. After filtration, an aliquot is evaporated and defatted by liquid-liquid partitioning. The extract is submitted to silica gel minicolumn cleanup and the final extract is concentrated and submitted to two-dimensional thin-layer chromatography (TLC). The identity of aflatoxins B1 and M1 is confirmed with trifluoroacetic acid (TFA) carried out on the thin-layer plate used for quantitation of these aflatoxins. The method permits the detection and confirmation of aflatoxins in liver in concentrations as low as 0.05 micrograms/kg. Average recoveries for aflatoxin M1 and aflatoxin B1 at spiking levels of 0.2 micrograms/kg were found to be 65% and 85%, respectively. With this method, 73 samples of bovine liver, 70 samples of porcine liver, and 56 samples of chicken liver taken from different slaughterhouses were investigated. In one sample of bovine liver, aflatoxins B1, B2, and M1 could be detected in concentrations of 0.10, 0.03, and 0.08 micrograms/kg, respectively.

Liquid chromatographic determination of aflatoxins in feedstuffs containing citrus pulp.

A liquid chromatographic (LC) method was developed for the determination of aflatoxins in feedstuffs containing citrus pulp. The feed-stuff sample is extracted with chloroform, followed by Sep-Pak Florisil cartridge cleanup and Sep-Pak C18 cartridge cleanup. The final eluate (water-acetone, 85 + 15, v/v) is submitted to reverse-phase liquid chromatography with water-methanol-acetonitrile (130 + 70 + 40, v/v/v) as mobile phase and postcolumn derivatization with iodine. Citrus components are removed from the extract efficiently. The limit of detection for aflatoxin B1 is less than 1 microgram/kg. Other aflatoxins can also be detected and measured. Recoveries of aflatoxins B1, B2, G1, and G2 for dairy rations spiked at 13, 5, 10, and 4 micrograms/kg were 87, 86, 81, and 82%, respectively. Corresponding coefficients of variation were 3.1, 3.6, 5.2, and 3.8%, respectively.

Comparison of six methods of analysis for the determination of aflatoxin B1 in feeding stuffs containing citrus pulp.

Six published methods of analysis for the determination of aflatoxin B1 have been compared for their suitability to determine aflatoxin B1 in feeding stuffs containing citrus pulp. These methods are the official European Community (EC) procedure, four procedures proposed in the European Community to replace this method and a new procedure developed by the authors of this article. In all procedures chloroform is used for initial extraction. Various clean-up systems are then applied. For the ultimate separation and detection, use is made of high performance liquid chromatography (HPLC) in three procedures and two-dimensional thin layer chromatography (TLC) in two procedures. One method allows either HPLC or TLC. All experiments were carried out with samples of a batch of feeding stuff containing citrus pulp, artificially contaminated with aflatoxins B1, B2, G1 and G2 at levels of ca 13, 5, 10 and 4 micrograms/kg respectively. Three methods were found to be suitable: a procedure in which gel permeation clean-up and two-dimensional TLC are used; a procedure in which TLC clean-up and reverse phase HPLC with postcolumn derivatization are used: a procedure in which cartridge clean-up and either HPLC or TLC are used. The latter method is preferred because its efficient clean-up yields a very clean extract, allowing the application of various systems of HPLC or TLC. Published recovery data of these three methods for aflatoxin B1 vary from 85-90% at a level of ca 10 micrograms/kg feeding stuff.