Accredited laboratory for detection of irradiated foods in Poland

The history of the development and the role of the Accredited Laboratory for Detection of Irradiated Foods in the national quality food control system are described. The analytical methods for the detection of irradiation in foods adapted and accredited in the Laboratory are enumerated and discussed.     

Suitability of the thermoluminescence method for detection of irradiated foods

Irradiated foods can be detected by thermoluminescence (TL) of contaminating minerals. Altogether about 300 lots of herbs, spices, berries, mushrooms and seafood were studied by the TL method. Irradiated herbs and spices were easily differentiated from unirradiated ones two years after irradiation of a 10 kGy dose. The mineral composition of seafood was variable; and while calcite was suitable for the TL analysis, aragonite and smectite gave unreliable results. Control analyses during two years confirmed the reliability of TL method.     

Evaluation of the novel Soxflo technique for rapid extraction of crude fat in foods and animal feeds

The new Soxflo instrument was evaluated for the determination of crude fat in foods and animal feeds. Samples are packed into small columns and extracted with petroleum ether at room temperature. The Soxflo yielded accurate data from foods, ranging from 0.4 to 73.2% crude fat, compared with Soxhlet extractions and Certified Reference Materials, for which recoveries averaged 99.7 and 100.7%, respectively. Relative standard deviations (1.81%) were approximately half those of Soxhlet extractions (3.68%). Regression analysis of the data suggested that there was no proportional bias. A small but acceptable constant bias was measured. Soxflo extractions are easy to perform and take approximately 1 h to complete. The main difference between the Soxflo and Soxhlet techniques lies in the extraction procedure. Estimated savings during extractions are in time (85% reduction), energy (95%), cooling water (100%), and solvents (50%). Soxflo extractions are, therefore, more environmentally friendly than Soxhlet extractions.     

Review: Authentication and traceability of foods from animal origin by polymerase chain reaction-based capillary electrophoresis

This work presents an overview of the applicability of PCR-based capillary electrophoresis (CE) in food authentication and traceability of foods from animal origin. Analytical approaches for authenticating and tracing meat and meat products and fish and seafood products are discussed. Particular emphasis will be given to the usefulness of genotyping in food tracing by using CE-based genetic analyzers.     

Food irradiation: regulatory aspects in the Asia and Pacific region

Irradiation treatment of food is becoming an increasingly accepted processing option for countries in the Asia Pacific region wishing to meet growing sanitary and phytosanitary requirements in international trade. There remain however, large differences between the regulatory requirements in the countries in this region.

This paper gives an outline on existing food irradiation regulations in the separate countries of the Asia Pacific region. New developments such as the recent decision by the Australia New Zealand Food Authority to start assessing applications for food irradiation treatment are discussed. Australia's intention to regulate the export of food treated by irradiation will also be outlined.

Details of the decision to harmonise food irradiation regulations by 13 countries in the Asia Pacific region based on conformance with Codex requirements is outlined. The likelihood of other Asia Pacific countries enacting similar harmonisation of their regulations will be examined. Future development such as certification of irradiation as a sanitary treatment for food are discussed. The expected result of these initiatives is a likely increase in irradiated foods traded within the Asia Pacific region.     

Effective PCR detection of animal species in highly processed animal byproducts and compound feeds

In this paper we present a polymerase chain reaction (PCR)-based method for detecting meat and bone meal (MBM) in compound feedingstuffs. By choosing adequate DNA targets from an appropriate localisation in the genome, the real-time PCR method developed here proved to be robust to severe heat treatment of the MBM, showing high sensitivity in the detection of MBM. The method developed here permits the specific detection of processed pig and cattle materials treated at 134 °C in various feed matrices down to a limit of detection of about 0.1%. This technique has also been successfully applied to well-characterised MBM samples heated to as high as 141 °C, as well as to various blind feed samples with very low MBM contents. Finally, the method also passed several official European ring trials.     

Standard reference materials for foods and dietary supplements

Well-characterized certified reference materials are needed by laboratories in the food testing, dietary supplement, and nutrition communities to facilitate compliance with labeling laws and improve the accuracy of information provided on product labels, so that consumers can make good choices. As a result of the enactment of the Nutrition Labeling and Education Act of 1990 and the Infant Formula Act of 1980, the National Institute of Standards and Technology (NIST) worked to develop a series of food-matrix standard reference materials (SRMs) characterized for nutrient concentrations. These include SRM 1544 Fatty Acids and Cholesterol in a Frozen Diet Composite, SRM 1546 Meat Homogenate, SRM 1548a Typical Diet, SRM 1566b Oyster Tissue, SRM 1846 Infant Formula, SRM 1946 Lake Superior Fish Tissue, SRM 1947 Lake Michigan Fish Tissue, SRM 2383 Baby Food Composite, SRM 2384 Baking Chocolate, SRM 2385 Slurried Spinach, and SRM 2387 Peanut Butter. With the enactment of the Dietary Supplement Health and Education Act of 1994, NIST has been working to develop suites of dietary supplement SRMs characterized for active and marker compounds and for toxic elements and pesticides, where appropriate. An updated SRM 1588b Organics in Cod Liver Oil, a suite of ephedra-containing materials (SRMs 3240–3245), a carrot extract in oil (SRM 3276), and a suite of ginkgo-containing materials (SRMs 3246–3248) are available. Several other materials are currently in preparation. Dietary supplements are sometimes provided in forms that are food-like; for these, values may also be assigned for nutrients, for example SRM 3244 Ephedra-Containing Protein Powder. Both the food-matrix and dietary supplement reference materials are intended primarily for validation of analytical methods. They may also be used as “primary control materials” in assignment of values to in-house (secondary) control materials to confirm accuracy and to establish measurement traceability to NIST.     

Analysis of the fusariotoxins zearalenone and vomitoxin (deoxynivalenol) in human foods and animal feeds by high-performance liquid chromatography (HPLC)

Summary HPLC procedures for analyses of the fusariotoxins zearalenone and vomitoxin in individual food- and feedstuffs as well as in mixed feed are described. Zearalenone is separated on a column with polar stationary phase (25 cm × 4.6 mm i.d., particle size 7 m), eluted with a chloroform-isooctane (75/25, v/v)+1.5% methanol mixture and detected fluorometrically. The quantitative determination was possible in all analyzed samples with a detection limit of 2g/kg with 70–80% recovery. Vomitoxin is fractionated by HPLC (C ₁₈ ¹ column, 25 cm×4 mm i.d., 5 m particle size) with water-methanol (60/40, v/v) mobile phase and determined by combining GLC or TLC with UV detection. The detection limit in mixed feed with interfering substances was 25 g/kg (recovery 25–35%). The separation by HPLC makes preparation of pure vomitoxin possible. The described methods are fast, simple and low cost and are suitable for routine analyses.     

Broad specificity indirect competitive immunoassay for determination of nitrofurans in animal feeds

A generic hapten of nitrofurans was synthesized by derivatization of 5-nitrofurfural with diamine, and the hapten was coupled to carrier protein to prepare different immunogens and coating antigens by using diazotization method and glutaraldehyde method. The obtained novel polyclonal antibodies from immunized rabbits showed broad cross reactivity among seven nitrofurans. After assessment of four coating antigen/antibody combinations, an indirect competitive immunoassay was developed to simultaneously detect the seven nitrofurans in animal feeds. The limits of detection for these analytes were in the range of 5-16 μg kg⁻¹ depending on the compound. Recoveries from nitrofurans fortified blank feeds at levels of 30 and 100 ng g ⁻¹ were in a range of 82.6-108.4% with coefficients of variation lower than 11.4%. The immunoassay was further validated by a HPLC method and the two methods showed good correlation (r = 0.9924). Therefore, the proposed immunoassay could be used as a practical method to monitor the illicit use of nitrofurans in animal feeds.     

Guidelines for in-house validation of analytical methods for pesticide residues in food and animal feeds

Criteria are presented by which analytical methods may be judged to have been validated for the determination of pesticide residues. All stages of analysis are addressed, from initial preparation of samples to the production of results, but with a focus on simplicity and cost-effectiveness of the requirements. Criteria are provided for both quantitative and qualitative (screening) methods and they may be applied to single- or multi-residue methods.     

Enzyme-linked immunosorbent assay and colloidal gold immunoassay for sulphamethazine residues in edible animal foods: investigation of the effects of the analytical conditions and the sample matrix on assay performance

To determine sulphamethazine (SMZ) residues in edible animal foods (pig muscle, chicken muscle, egg, fish, milk and liver), a competitive direct enzyme-linked immunosorbent assay (ELISA) and a colloidal gold immunoassay were established. The limits of detection of the ELISA and the colloidal gold immunoassay were 0.02 and 0.5 μg kg⁻¹, respectively. The specificity of the ELISA developed to the SMZ was high according to the results of cross-reactivity testing with 14 kinds of sulphonamides. To obtain a more sensitive immunoassay, buffer solution (30 mmol L⁻¹ phosphate-buffered saline with 0.05% Tween 20, pH 8.5) was optimized through the whole test procedure. A simple and efficient extraction method for the rapid detection of SMZ residues in foods was developed, with recoveries between 74 and 117.5%. Matrix effects can be avoided by 1:10 dilution of pig muscle, chicken muscle, egg, fish, milk and liver with optimal buffer. The detection limit of SMZ was 5 μg kg⁻¹ in liver and 2 μg kg⁻¹ in the other five samples. For the validation of the ELISA tests, sample extracts were analysed by ELISA and high-performance liquid chromatography. The results obtained by these two methods showed a good correlation (r ²) which was greater than 0.9. The colloidal gold immunoassay presented in this assay was successfully applied to determine SMZ in pig muscle, milk and fish below or equal to the maximum residue level (20 μg kg⁻¹).     

The modular analytical procedure and validation approach and the units of measurement for genetically modified materials in foods and feeds

Food and feed analysts are confronted with a number of common problems, irrespective of the analytical target. The analytical procedure can be described as a series of successive steps: sampling, sample processing, analyte extraction, and ending, finally, in interpretation of an analytical result produced with, e.g., real-time polymerase chain reaction. The final analytical result is dependent on proper method selection and execution and is only valid if valid methods (modules) are used throughout the analytical procedure. The final step is easy to validate-the measurement uncertainty added from this step is relatively limited and can be estimated with a high degree of precision. In contrast, the front-end sampling and processing steps have not evolved much, and the corresponding methods are rarely or never experimentally validated according to internationally harmonized protocols. In this paper, we outlined a strategy for modular validation of the entire analytical procedure, using an upstream validation approach, illustrated with methods for genetically modified materials that may partially apply also to other areas of food and feed analyses. We have also discussed some implications and consequences of this approach in relation to reference materials, measurement units, and thresholds for labelling and enforcement, and for application of the validated methods (modules) in routine food and feed analysis.     

Spectrophotometric enzymatic cycling method using -glutamate dehydrogenase and -phenylglycine aminotransferase for determination of -glutamate in foods

This report describes a new spectrophotometric method capable of determining low levels of -glutamate. The assay is based on substrate cycling between -glutamate dehydrogenase (GlDH) and the novel enzyme -phenylglycine aminotransferase ( -PhgAT). In this system, GlDH converts -glutamate to 2-oxoglutarate with concomitant reduction of NAD⁺ to NADH. The 2-oxoglutarate is recycled to -glutamate in a transamination reaction catalyzed by -PhgAT using -4-hydroxyphenylglycine as an amino donor, which is converted to 4-hydroxybenzoylformate. Both NADH and 4-hydroxybenzoylformate strongly absorb UV light at 340 nm (_340nm=6.22×10³ and 8.90×10³ l mol⁻¹ cm⁻¹, respectively). The signal amplification effect of the cycling reactions is thus further enhanced by the combined absorption of the two accumulating reaction products. The standard calibration curve for -glutamate was linear from 0.2 to 20 μM, with a detection limit of 0.14 μM. Food samples can be significantly diluted before subjected to the assay, thus reducing the effects of interfering substances. Because of the unique substrate specificity of -PhgAT, -glutamate could be selectively determined in the presence of other common amino acids at relatively high concentrations. The assay was satisfactorily applied to measure -glutamate in various kinds of food products. The procedure is simple, rapid, accurate, and should be easily automated.     

Analytical methods applied to the determination of pesticide residues in foods of animal origin. A review of the past two decades

Pesticides are widely used in agriculture and can be transferred to animals in a number of ways. Consequently, reliable analytical methods are required to determine pesticide residues in foods of animal origin. The present review covers published methods and research articles (1990-2010) in which pesticide residues have been extracted from meat and meat products, milk and dairy products, fish and seafood, and eggs, then cleaned up, and isolated by chromatographic techniques to be identified and quantified by various detection methods. Recovery rates, quantification limits, the matrix effect and related parameters have all been considered. Lastly, future developments in this field are outlined.     

Description and validation of an analytical method for the determination of paromomycin sulfate in medicated animal feeds

A procedure for the extraction of paromomycin from different animal feed matrices (rabbit, chicken, pig feeds) and its subsequent determination via a reversed-phase ion-pair HPLC separation coupled with pulsed amperometric detection is described. The procedure optimised in terms of the extracting solvent and the solid phase extraction stationary phase allows the total recovery of the aminoglycoside antibiotic. The criteria used for the validation of the analytical method applied to the cited matrices are the linear dynamic range of the response, the detection limit, the repeatability, the intermediate repeatability and the accuracy. A comparison with a method described in the literature for the bulk analysis of this antibiotic is made.     

One-way and two-way pulsed electromembrane extraction for trace analysis of amino acids in foods and biological samples

In the present work, pulsed electromembrane extraction (PEME) was performed for the first time, as a new concept of electrically enhanced microextraction method, for extraction and quantification of histidine, phenylalanine and tryptophan in different matrices. PEME offers an alternative to conventional electromembrane extraction (EME), which faces problems such as serious instabilities in the analysis of real samples with high concentration levels of ions. In these samples, increasing of the ion transportation across the liquid membrane results in Joule heating during the extraction process which may follow by punctuation of the organic membrane, increasing of the current level and bubble formation due to electrolysis reactions. A mixture of 2-nitrophenyl octyl ether (NPOE), di-(2-ethylhexyl) phosphate (DEHP) and tris-(2-ethylhexyl) phosphate (TEHP) was immobilized in the pores of hollow fiber as the organic liquid membrane. Other effective parameters such as extraction time, ion balance and pulse frequency were optimized using the experimental design. Extraction recoveries in the range of 7.1–21.6% and satisfactory repeatability (2.1 < CV% < 4.5) were obtained. Limits of detection were 5, 10 and 30 ng mL⁻¹ for tryptophan, phenylalanine and histidine, respectively. The method offers acceptable linearity with correlation coefficients higher than 0.9979. Furthermore, the figures of merit of PEME are compared with the results from conventional electromembrane extraction (EME), which proves the advantages of the proposed technique. The method was applied to the determination and quantification of amino acids in foods and biological samples. Also, two-way PEME was employed as a novel approach for highly selective extraction of tryptophan as a model analyte to introduce an interesting ability of the proposed technique.     

Microwave-assisted on-line derivatization for sensitive flow injection fluorometric determination of formaldehyde in some foods

A rapid and sensitive flow injection fluorometry has been developed for the determination of formaldehyde based on the microwave on-line accelerating its Hantzsch reaction with cyclohexane-1,3-dione. Under the optimized conditions, the fluorescent intensity is proportional to formaldehyde content in the range from 0.05 ng/mL to 2.000 μg/mL. The detection limit (S/N = 3) is 0.02 ng/mL and the analytical frequency is 28 injections per hour. The relative standard deviations are 2.2% and 3.1% for eleven injections of 0.100 and 0.001 μg/mL of formaldehyde, respectively. With the assistance of microwave irradiation, a best sensitive fluorometry was established for the determination of formaldehyde at a high analytical frequency. This method was successfully applied to food analysis without requiring any sample pretreatment, and the determination results were correlated well with those obtained by the standard method with a sample pretreatment of steam distillation.     

Determination of inorganic elements in animal feeds by NIRS technology and a fibre-optic probe

In the present work we study the use of near infra-red spectroscopy (NIRS) technology together with a remote reflectance fibre-optic probe for the analysis of the mineral composition of animal feeds. The method allows immediate control of the feeds without prior sample treatment or destruction through direct application of the fibre-optic probe on the sample.The regression method employed was modified partial least squares (MPLS). The calibration results obtained using forty samples of animal feeds allowed the determination of Fe, Mn, Ca, Na, K, P, Zn and Cu, with a standard error of prediction (SEP(C)) and a correlation coefficient (RSQ) of 0.129 and 0.859 for Fe; 0.175 and 0.816 for Mn; 5.470 and 0.927 for Ca; 2.717 and 0.862 for Na; 4.397 and 0.891 for K; 2.226 and 0.881 for P; 0.153 and 0.764 for Zn, and 0.095 and 0.918 for Cu, respectively.The robustness of the method was checked by applying it to 10 animal feeds samples of unknown mineral composition in the external validation.