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PubMed2004

Survey of persistent organochlorine contaminants (PCBs, PCDD/Fs, and PAHs), heavy metals (Cu, Cd, Zn, Pb, and Hg), and arsenic in food samples from Huelva (Spain): levels and health implications.

Concentrations of PCBs, PCDDs, and PCDFs, heavy metals (Cu, Cd, Zn, Pb, and Hg), and arsenic have been determined in a great variety of food samples purchased in different markets across the city of Huelva, located in southwestern Spain and under strong industrial activity. All samples analyzed presented concentrations below the maximum allowed by the European Community regarding PCDD/Fs, with the exception of samples within the meat group. An estimation of the daily intake resulted in 1.15 pg of WHO(PCDD/Fs)-TEQ/kg of body weight/day for a 70 kg person and 2.63 pg of WHO-TEQ/kg of body weight/day when PCBs were included, therefore accounting for a similar or even higher percentage than PCDD/Fs and showing the importance of their inclusion in monitoring studies. Meat and meat products, together with vegetable oils and dairy products, were the major food groups contributing to the estimated daily intake. For heavy metals and arsenic, the concentrations found were under the value proposed by European regulations, and estimated daily intakes were well below those proposed by the WHO for all metals investigated. PAHs have been analyzed in food samples from marine origin, values ranging from 8.22 to 71.4 ng/g of fresh weight. Pyrene was the most abundant compound, accounting for >80% in the samples investigated. The most carcinogenic PAHs, such as benzo[a]pyrene and dibenz[a,h]anthracene, were in all cases below the limits of detection. Therefore, the samples analyzed in this survey can be considered as safe with regard to the levels obtained and the in-force legislation.

Arsenic↗

PubMed1999

PCDDs and PCDFs in food samples from Catalonia, Spain. An assessment of dietary intake.

Food samples from local markets and supermarkets of Tarragona (Catalonia, Spain) were analyzed for PCDD/F concentrations. On lipid basis, PCDD/F levels in meat, fish, eggs, and fats and oils were similar or lower than those found in other countries. By contrast, in general terms PCDD/F levels in milk, vegetables, and cereals showed higher levels than those previously reported. The total dietary PCDD/F intake by the population of Tarragona was estimated to be 210 pg I-TEQ/day. This value is higher than the dietary intake of PCDD/Fs found in a number of surveys from other countries. However, when total dietary intake of PCDD/Fs was calculated including only fish and seafood, meat, milk and dairy products, eggs, and fats and oils, a dietary intake of PCDD/Fs of 117 pg I-TEQ/day was obtained. This intake is in the same range than that reported for different regions and countries. The results of the present study show that food groups such as vegetables, fruits, and cereals should not be excluded to estimate the total dietary intake of PCDD/Fs by general populations, especially in those countries and/or regions in which their consumptions are notable.

Adult↗

PubMed2001

Combination of immunomagnetic separation and polymerase chain reaction for the simultaneous detection of Listeria monocytogenes and Salmonella spp. in food samples.

A method that combined the immunomagnetic separation (IMS) technique and the multiplex polymerase chain reaction (PCR) method (i.e., the IMS-mPCR method) was developed for simultaneous detection of Listreria monocytogenes and Salmonella spp. in food samples. When only the multiplex PCR method was used, it was found that if cell numbers of each of the two target organisms (L. monocytogenes and Salmonella spp.) were above the detection limit, but differed by more than 2 logs-e.g., n x 10(7) to n x 10(4) or n x 10(6) to n x 10(3)--the organism presenting the lower numbers might go undetected. Following the enrichment step with universal preenrichment (UP) broth, if an IMS method using equal quantities of anti-Listeria and anti-Salmonella immunomagnetic beads was performed prior to PCR, both pathogens could be detected unambiguously. Such results could be obtained for target organisms in food samples, such as milk, dairy, and meat products, if similar enrichment and IMS steps were performed prior to PCR.

Colony Count, Microbial↗

PubMed1999

Detection of Salmonella contamination in food samples by dot-ELISA, DNA amplification and bacterial culture.

A dot-blot enzyme-linked immunosorbent assay (dot-ELISA) employing a genus Salmonella specific monoclonal antibody (MAb) was used for detection of the bacteria in food samples in comparison with the conventional culture method and the DNA amplification. Among the 200 chicken and pork samples (100 each) tested, 9% and 33%, 7% and 20% and 7 and 23% were positive for salmonellae by the dot-ELISA, the culture method and the DNA amplification, respectively. Statistical analyses revealed that the sensitivity, specificity, efficacy, and positive and negative predictive values of the detection of Salmonella in the food samples by dot-ELISA compared with the culture method were 93.33%, 91.76%, 92%, 66.66% and 98.73%, respectively. Comparison of the DNA amplification and the culture method revealed the sensitivity, specificity, efficacy, and positive and negative predictive values of 100%, 91.58%, 92%, 65.21% and 100%, respectively. The dot-ELISA and the DNA amplification results were in a better agreement when the two assays were compared. The sensitivity, specificity, efficacy, positive and negative predictive values of the dot-ELISA compared to the DNA amplification were 91.3%, 100%, 98%, 100% and 97.5%, respectively. From this study, the dot-ELISA is rapid, simple, sensitive, specific at low cost with limited amount of infectious waste to be disposed and offers another advantage in that it detects only the smooth LPS of Salmonella which implies the possible presence of the virulent organisms.

Animals↗

PubMed1995

PCR and gene probe identification of botulinum neurotoxin A-, B-, E-, F-, and G-producing Clostridium spp. and evaluation in food samples.

A degenerate primer pair was selected to amplify specifically a 260-bp DNA fragment from Clostridium botulinum types A, B, E, F, and G, and five individual probes allowed identification of each toxinotype by hybridization of the PCR products. The 72 strains of different Clostridium species tested and 11 other bacterial species commonly found in food samples gave an amplification product. This assay was able to detect 1 C. botulinum type A or B and 10 C. botulinum type E strains per reaction. With 184 artificially contaminated food samples, after an 18-h enrichment step, the sensitivity was 10 bacteria per g of sample and the correlation with the mouse bioassay reached 95.6%.

Bacterial Typing Techniques↗

PubMed2000

Rapid combined assay for Salmonella detection in food samples.

A rapid method was developed to detect salmonellae in food samples. The method gave a possibility to obtain results after 28 h 30 min. The preenrichment in buffered peptone water lasted for 6 h, the enrichment in Rappaport-Vassiliadis medium was applied for 18 h followed by PCR with INVA1-INVA2 primer pair, adapting Chiu and Ou's method. This procedure was suitable to demonstrate salmonella contamination at min. 10 cfu/25 g sample. Out of 18 samples there was a good agreement between the results of the conventional and rapid methods in case of 17 samples. PCR with SPVC1-SPVC2 primer pair informing about the presence of virulence plasmid was performed in separate tubes, because decreased sensitivity was observed in case of multiplex PCR.

Culture Media↗

PubMedDate not supplied

Use of specific oligonucleotides for direct enumeration of Listeria monocytogenes in food samples by colony hybridization and rapid detection by PCR.

Two 18-mer oligonucleotides derived from the sequence of hly, the gene coding for listeriolysin O, were shown to be specific for Listeria monocytogenes in the genus Listeria in colony hybridization tests. The oligonucleotides did not hybridize with any of the bacterial species found in food and co-isolated with Listeria on selective media. They were used in colony hybridization tests for enumeration of L. monocytogenes present in food samples after direct plating on selective media plates. In addition, two 24-mer oligonucleotides, each including the sequence of one of the 18-mers, were successfully used for the PCR-based detection of L. monocytogenes bacilli present in food samples after 48-h enrichment period. Using this technique, as little as 10(2) bacteria per ml of enrichment broth can be detected.

DNA, Bacterial↗

PubMed1977

Confirming heptachlor and heptachlor epoxide in food samples by gas-liquid chromatography of their photoderivates.

The food sample extract is cleaned up on a Florisil column and the 6% ethyl ether in petroleum ether cluate is subjected to repeated concentrations, using a micro-Snyder column, to expel volatile materials that absorb ultraviolet (UV) light. The sample and standard solutions of heptachlor and heptachlor epoxide are placed in quartz cells and exposed to UV radiation in the dark. Characteristic photoderivatives of the respective pesticides which form in the sample extract are identified and measured by comparison with those formed in the irradiated standard solutions, using electron capture gas-liquid chromatography. Recoveries of the 2 pesticides from 13 products, fortified at levels from 0.01 to 0.3 ppm and determined after derivatization, ranged from 67 to 110%.

Chromatography, Gas↗

PubMed2006

Evaluation of a gas chromatography/mass spectrometry method for the quantification of carboxymethyllysine in food samples.

An accurate method for the quantification of carboxymethyllysine (CML) in food samples is evaluated. CML, a stable advanced Maillard compound, is considered as an useful marker of protein damage in severely heated foods. The proposed GC-MS method stipulates double derivatisation of amino acids and quantification by selected ion monitoring. Relative error of repeatability was further improved from 5 to 1% by replacing internal standard by isotope dilution. Comparison with enzyme linked immunosorbent assay (ELISA) was performed on infant formulas, with satisfactory results in powdered but not in liquid formulas. Quantification of CML in several food matrices allowed evidencing CML formation in food products containing reducing sugar only.

Enzyme-Linked Immunosorbent Assay↗

PubMed1983

Automated gas chromatographic analysis of pesticide residues in food samples by means of fused-silica capillary columns and data processing.

A conventional gas chromatograph with one system for split and splitless injection and one on-column injection system for fused-silica capillary columns and the two selective nitrogen-phosphorus and electron-capture detectors is applied to pesticide residue analysis in food samples. The gas chromatograph is equipped with a two-channel data processor that can be programmed with BASIC. Additionally an autosampler is used with the splitless injector. This automated injection system is connected to a 25-m methylsilicone fused-silica column which is coupled via an effluent splitter parallel to both detectors and used for screening in routine analysis. Calibration is performed on this column by means of three calibration test mixtures which include three internal standards. All compounds are calibrated on both detectors in parallel and the response calculated as an additional identification parameter. After the analysis of a of food samples together with the calibration mixture a report is plotted, containing all pesticide residues which may be present in the samples and their tentative quantities. The final confirmation is achieved on the second column, coated with methylphenyl-silicone phase, connected to the on-column injector.

Autoanalysis↗

PubMedDate not supplied

The occurrence of phthalate ester and di-2-ethylhexyl adipate plasticizers in Canadian packaging and food sampled in 1985-1989: a survey.

Selected foods (260 samples) packaged in materials with the potential to contribute plasticizers to the food, and available food composites (98 samples) obtained from the Canadian Health Protection Branch Total Diet Program, were analysed for phthalate plasticizers and di-2-ethylhexyl adipate (DEHA). The available contacting packaging was also analysed for plasticizers. The results show DEHA in food-contacting film and as a migrant in store-wrapped meat, poultry, fish, cheese and ready-to-eat foods at levels as high as 310 micrograms/g (cheese). DEHA levels in unheated film-wrapped ready-to-eat foods were increased by heating. The di-2-ethylhexyl, dibutyl, butylbenzyl and diethyl phthalate esters (DEHP, DBP, BBP and DEP, respectively) were also found in both the packaging and the contacted foods. Low levels of DEHP (0.065 micrograms/g, average in beverages and 0.29 micrograms/g, average in foods) associated with the use of DEHP-plasticized cap or lid seals, were found in a variety of glass-packaged foods; DBP, BBP and DEHP were found, as previously described, in butter and margarine as migrants from the aluminium foil-paper laminates; and DEP in pies at 1.8 micrograms/g (average) as a migrant from the pie carton windows. In most cases, plasticizers detected in the food were also found in the associated packaging. When possible, 'core' or non-contacting food portions were analysed to verify the migration phenomena.

Adipates↗

PubMed1998

Investigation of photochemical behavior of pesticides in a photolysis reactor coupled on-line with a liquid chromatography-electrospray ionization tandem mass spectrometry system. Application to trace and confirmatory analyses in food samples.

The photochemical behavior of pesticides in a photolysis reactor coupled on-line with a liquid chromatography-electrospray ionization mass spectrometer (LC-hv-MS) was investigated. This paper describes the application of LC-hv-MS, in combination with tandem mass spectrometry (MS-MS), to identification of phototransformation products and to the establishment of possible photolytic pathways of pesticides. In addition, the applicability of LC-hv-MS as an alternative to LC-MS-MS, for trace and confirmatory multiresidue analysis in food samples was investigated. To demonstrate the potential of this technique, a series of N-heterocyclic compounds, phenylureas and carbamates, was studied. Several parameters, such as irradiation time and nature of photosensitizers, were investigated, and their impact on the photolytic transformation is presented here. The technique's versatility is also exhibited by using it for identification of triazine isomers, and for detection of pesticide residues in food sample extracts. Illustrative applications for analysis in lettuce and blueberry extracts are described.

Food Contamination↗

PubMed2004

An improved PCR primer pair based on 16S rDNA for the specific detection of Salmonella serovars in food samples.

Salmonella serovars are some of the major bacterial pathogens that can cause sporadic cases and outbreaks of foodborne illness. Based on the sequence data in the V3 region of the 16S rRNA gene, two PCR primer pairs have been designed for the detection of all serovars of Salmonella. However, none of these primers were specific for Salmonella because complete sequence homology with certain non-Salmonella strains has been found within each of them. Thus, the specificities of these two primer pairs could not rely on only one of the two primers. In this study, we modified our previous 16SFI primer by extending one base at the 5' end and three bases at the 3' end. The modified primer, 16S-Sal, was designed with one or more mismatched bases near the 3' end of the primer annealing to the corresponding sequences of non-Salmonella strains. Such modification eliminates interference from Citrobacter freundii and Enterobacter cloacae as occurs with the 16SFI primer. When 16S-Sal and a degenerate primer, 16S-CCR, were used as a primer pair, detection specificity of Salmonella serovars was achieved. Because this primer pair was used for PCR detection of the salmonellae in food samples, such as whole milk and chicken meat, as low as 1 to 9 CFU/g (ml) of the food sample could be detected when a 8-h preculture step was performed prior to the PCR. For chicken meat, the endogenous microflora did not interfere with the PCR results.

Animals↗

PubMed2000

Application of gel permeation chromatography and HPLC method with fluorescence detector to determination of benzo(a)pyrene in food samples.

During the last three decades contamination of food by traces of toxic substances has been the object of intensive research in modern food toxicology. Various classes of compounds of different origin were detected in food and beverages. In particular nitrosamines and polynuclear aromatic hydrocarbons attracted attention, due to their mutagenic and cancerogenic potential (1, 2). Traces of PAHs have been detected in many foods, including vegetables, vegetable oils, fruits, grains, sea food, grilled and roasted meat, smoked fish, coffee and tea. PAHs in food are only a part of the general problem of PAH pollution in the environment. The numerous types of PAHs--some 100 have been isolated and identified in food and in the environment--are a challenge to modern analytical technique. Various chromatographic procedures, including column, paper and thin layer chromatography have been applied to isolate these substances from contaminated samples. Some of these methods give satisfactory results, especially in the determination of single PAHs including benzo(a)pyrene (3). Gas chromatography and HPLC are the techniques most widely used to meet these analytical demands. Very important are pretreatment of food samples and clean-up procedures. In Slovakia limits for B)a)P in food are: 0.001 mg/kg in smoked meat and fish products; 0.003 mg/kg in paprika, pepper, sausages. Other PAHs (from US EPA 16 PAH) have no limits. This paper describes determination of benzo(a)pyrene in different food samples by gel permeation chromatography and the HPLC method with a fluorescence detector. State Veterinary Institute (SVU) in Dolný Kubín (Slovakia) is authorized for determination of benzo(a)pyrene in all samples, which are imported to Slovakia. Many samples with excessive of benzo(a)pyrene were from Baltic Sea (especially smoked sprats).

Benzo(a)pyrene↗

PubMed2006

Novel voltammetric biosensor for determining acrylamide in food samples.

Recent findings showing that acrylamide is formed in heat-treated foods rich in asparagine and reducing sugars such as glucose, have accelerated the needs for the development of new analytical methods to determine this potential human carcinogen. Acrylamide forms adduct with hemoglobin (Hb) as a result of the reaction with the alpha-NH2 group of N-terminal valine of Hb. This interaction is the basis of a new voltammetric biosensor to detect acrylamide. The biosensor was constructed using a carbon-paste electrode modified with hemoglobin (Hb), which contains four prosthetic groups of heme--Fe(III). Such an electrode displays a reversible reduction/oxidation process of Hb-Fe(III)/Hb-Fe(II). Interaction between Hb and acrylamide was observed through decreasing of the peak current of Hb-Fe(III) reduction. The electrodes presented a very low detection limit (1.2 x 10(-10)M). The validation made in the matrix obtained by water extraction of potato chips showed that the electrodes presented are suitable for the direct determination of acrylamide in food samples.

Acrylamide↗

PubMed1997

Detection of Salmonella from raw food samples using Dynabeads anti-Salmonella and a conventional reference method.

A Dynal core method has been established using Dynabeads anti-Salmonella to detect Salmonella from all categories of food samples. The protocol consists of the standard pre-enrichment of samples in buffered peptone water followed by immunomagnetic separation and subsequent selective enrichment of the bead-bacteria complexes in Rappaport-Vassiliadis Soya Peptone broth before plating onto Salmonella selective media. This modified IMS cultural method is intended to replace or augment traditional cultural methods used for Salmonella detection due to its specificity and increased sensitivity. The optional direct plating of bead-bacteria complexes onto solid media using a swab-streak technique is suitable for processed foods or samples known to have a history of very low resident flora. In an evaluation using 100 naturally contaminated samples, this IMS core method detected 39 of the 44 positive samples detected by all the methods combined, compared to 31 detected by the conventional ISO 6579 reference method. Furthermore, in ten different food matrices inoculated with low levels (1-5 cells/25 g) of twenty Salmonella serovariants, frozen for one month before being examined, the IMS core method, showed a 90% concordance with the ISO method and isolated two more Salmonella positive samples than the conventional ISO method.

Food Microbiology↗

PubMed1994

Simultaneous multielemental analysis of daily food samples by inductively coupled plasma mass spectrometry.

Several toxic elements in total composite food samples of hospital diets were determined simultaneously by inductively coupled plasma mass spectrometry (ICP-MS). Trace element concentrations of Be, Cr, As, Cd, Sn, Sb, Ce, Hg and Pb changed widely ranging from a few ng.g-1 to less than 3 micrograms.g-1 in all 24 samples collected through a year. Be, Sn, and Hg were not detected in rice sample alone, and other trace elements, with the exception of Cr and As, were less than approximately 50% levels, as compared with mixed diet samples. The daily intakes of these toxic elements were in the ranges of a few to several hundreds of micrograms.

Food Analysis↗

PubMed1989

A two-year study of the distribution of 'thermophilic' campylobacters in human, environmental and food samples from the Reading area with particular reference to toxin production and heat-stable serotype.

The incidence of 'thermophilic' campylobacters in foods and environmental samples has been studied over a two-year period. Of 781 environmental samples, 529 (67%) were found to contain campylobacters, and campylobacters were isolated from 835 (39%) of 2116 food samples. Sewage was almost always contaminated with campylobacters (96.6% of samples) and of the food samples both poultry (55.5%) and offal (47.0%) were commonly contaminated. Determination of the heat-stable serotypes of all strains isolated from these sources and of 921 strains isolated from human faeces showed that there was a wide distribution of serotypes in most types of sample. Serotype Pen 2 was the commonest type found in human faeces (18.9%) and it was also commonest in offal (21.3%), beef (40.0%), sewage (17.7%) and was the third commonest type in poultry. A comparison of culture media and conditions for optimal production of both cytotoxic and cytotonic enterotoxins showed that Brucella Broth incubated under microaerobic conditions for 24 h at 42 degrees C was suitable for both toxins. Detection of cytotoxic activity was most sensitive using HeLa cells. The sensitivities of two ELISA systems and a Chinese Hamster Ovary tissue culture assay for detection of cytotonic enterotoxin were comparable. Not all strains isolated from cases of enteritis in human beings produced toxin; 23.1% produced cytotonic enterotoxin and 17.5% produced cytotoxin. There was no correlation between serotype and toxin production. The wide distribution of campylobacters, indistinguishable from those isolated from cases of enteritis in human beings, leads us to conclude that simplistic statements suggesting that one particular type of food is primarily responsible for cases of human disease should not be made.

Animals↗