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PubMed2002

Comparison of a capillary electrophoresis method with high-performance liquid chromatography for the determination of biogenic amines in various food samples.

A capillary electrophoresis (CE) and a high-performance liquid chromatography (HPLC) method to analyze biogenic amines in food were compared. An automated precolumn derivatization with o-phthaldialdehyde (OPA) allows for the determination of aliphatic amines and amino acids by HPLC. In contrast, for the measurement of histamine and tyramine by CE, no laborious sample pretreatment was necessary. The biogenic amines were separated by CE or HPLC in less than 9 or 20 min, respectively. The calibration curves were linear to at least 100 mg/kg (r=0.999) and 1,000 mg/kg for HPLC and CE, respectively, with detection limits for histamine of 0.5 mg/kg (fluorescence detector) or 1 mg/kg (diode array detector) with HPLC and 2 mg/kg with CE. The detection limits for tyramine were 1.5 mg/kg with HPLC and 6 mg/kg with CE and for further amines (e.g., putrescine, spermidine, cadaverine, agmatine) ranging from 1.0 to 8.5 mg/kg with HPLC. There was a good correlation between CE and HPLC (correlation coefficient for histamine: 0.994).

Biogenic Amines↗
PubMed2003

Heteroduplex mobility assay for the identification of Listeria sp and Listeria monocytogenes strains: application to characterisation of strains from sludge and food samples.

One hundred and ten Listeria sp. isolates from sewage sludge were identified according to phenotypic and genotypic methods. The Listeria sp. strains isolated from five types of sludge from three sewage treatment plants in Angers (France) and the surrounding area included L. monocytogenes (55.5%), L. innocua (29.1%), L. seeligeri (13.6%) and L. welshimeri (1.8%). The majority of L. monocytogenes strains belonged to serotypes 4b, 1/2b and 1/2a. Moreover, a heteroduplex mobility assay based on the 16S rRNA sequences was tested for its ability to identify the six species of the genus Listeria. This study, performed on 283 Listeria sp. strains from human, food and sewage sludge samples, showed that all the species were distinguishable from one another. L. innocua and L. seeligeri showed respectively three and two distinct banding patterns. Within L. monocytogenes, four groups (I-IV) were defined. The majority of food and environmental isolates were clustered in group I and it is noteworthy that group IV clustered epidemiologic isolates and strains belonging to serotypes 4b, 1/2a and 1/2b.

Animals↗
PubMedDate not supplied

Comparison of the compact dry TC method with the standard pour plate method (AOAC official method 966.23) for determining aerobic colony counts in food samples: Performance-tested method.

Compact Dry TC qualifies as a rapid method kit for determining aerobic colony counts in foods. The plates are presterilized and contain culture medium and a cold-soluble gelling agent. The medium is rehydrated by inoculating 1 mL diluted sample into the center of the self-diffusible medium and allowing the solution to diffuse by capillary action. The plates can then be incubated and the colonies counted without any additional steps. The Compact Dry TC method was validated with 5 different raw meats. The performance tests were conducted at 35 degrees and 30 degrees C. In all required performance studies, no apparent differences were observed between the Compact Dry TC method and the Standard Pour Plate method (AOAC Official Method 966.23) for the detection level of aerobic microorganisms. For the accuracy claim (n = 60), a correlation factor of r2(35) = 0.9977 (35 degrees C) and r2(30) = 0.9932 (30 degrees C) could be assigned, as stated in the application for "Performance Tested Method." Quality consistency and storage robustness studies, showed no significant variations in plate count results with different production lots or plates of diverse storage age.

Bacteria, Aerobic↗
PubMedDate not supplied

Determination of allura red in some food samples by adsorptive stripping voltammetry.

Square wave (SW) voltammetry was used to explore the adsorption properties of the food additive dye Allura Red on a hanging mercury drop electrode (HMDE). By using the adsorptive stripping voltammetric approach, we developed a sensitive electroanalytical method for the determination of this azo dye. A well-developed voltammetric peak probably related to the cathodic reduction of the azo moiety was obtained in pH 9 Britton-Robinson (B-R) buffer at 613 mV. Cyclic voltammetric studies indicated that the reduction process was irreversible and primarily controlled by adsorption. The adsorptive voltammetric signal was evaluated with respect to various experimental conditions; the optimized values were supporting electrolyte, B-R buffer; pH 11; accumulation time, 180 s; accumulation potential, 0.0 V; scan rate, 900 mV/s; pulse amplitude, 75 mV; and SW frequency, 90 Hz. Adsorptive voltammetric peak current showed a linear response for Allura Red in the concentration range of 2.5 x 10(-8) to 2.0 x 10(-7) mol/L (r = 0.998). The limit of detection was 8.5 x 10(-9) mol/L (4.2 ng/mL), the precision in terms of relative standard deviation was 1.3%, and the mean recovery was 102%. Possible interferences by several substances usually present in food products such as food additive azo dyes (E110, E102), gelatin, natural and artificial sweeteners, preservatives, and antioxidants were also evaluated. The proposed electrochemical procedure was successfully applied to the determination of this food dye in commercially available candy and a soft drink. The results were compared by statistical evaluation with those obtained by a reference spectrophotometric method.

Azo Compounds↗
PubMedDate not supplied

Monitoring of pesticide residues in human milk, soil, water, and food samples collected from Kafr El-Zayat Governorate.

Pesticide residues in human milk and environmental samples from Kafr El-Zayat Governorate in Egypt were analyzed. This governorate is located near one of the biggest pesticide factories in Egypt. Organochlorine and organophosphorus pesticides were monitored, including those that have been prohibited from use in Egypt. Human milk samples (31 samples) from Kafr El-Zayat were compared with 11 samples collected from Cairo. Data were compared with results from studies performed in 1987 and 1990. The present study showed that aldrin and dieldrin, heptachlor and heptachlor epoxide, and endrin residues have been eliminated from human milk. Estimated daily intakes (EDIs) of DDT complex and gamma-HCH by breast-fed infants in Kafr El-Zayat were 85.96 and 3.1% of the respective acceptable daily intakes (ADIs). beta-HCH residues showed an increasing pattern, especially in human milk samples from Cairo. DDT complex and HCH isomers in orange, spinach, lettuce, potatoes, and clover samples ranged from undetectable to very low concentrations. Higher levels of DDT and HCH were detected, but aldrin, dieldrin, endrin, and the heptachlors were not detected in food of animal origin. Residues in fish samples were below maximum residue limits established by some developed countries. Those in animal milk samples approached the extraneous residue limits of the Codex Committee on Pesticide Residues. HCH residues in soil were negligible, but DDT residues in soil were somewhat higher. Among water samples, groundwater samples had the highest residues of HCHs and DDTs, followed by Nile River water and then tap water. However, the organochlorine pesticide residues were found at concentrations below the maximum allowable limits set by the World Health Organization for drinking water. Among 12 organophosphorus pesticides monitored as parent compounds, dimethoate, malathion, methamidophos, and chlorpyrifos residues were detected in low concentrations in soil samples from a pesticide factory. No organophosphorus pesticide residues were found in plant samples, except for very low residues of dimethoate in an orange sample. Water samples were devoid of organophosphorus residues as parent compounds.

Animals↗
PubMed2001

Influence of laboratory homogenization procedures on trace element content of food samples: an ICP-MS study on soft and durum wheat.

Sample contamination as a consequence of abrasion of grinding tools during the homogenization of food materials to be analysed for trace elements was addressed. The possible release of 15 trace elements (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Se, Sn, V, Zn) from six different grinding and milling devices, operating either continuously or discontinuously, was evaluated. All the devices were commercially available and were representative of models usually employed in food and agricultural laboratories. Wheat grains belonging to one soft and one durum cultivar were used as test material. The determination of the analyte concentrations in subsamples submitted to the different preparation treatments was performed by quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS). Accordingly, a suitable digestion method was developed and the ArC+ interference affecting Cr determination was evaluated and corrected. Statistical differences with respect to the control were detected for 10 elements (Al, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb) and in most cases contamination of the samples was traced back to the composition of the grinding equipment. None of the investigated devices was contamination-free with respect to all of the quantified elements. Abrasion of the grinding tools was higher with durum wheat than with soft wheat as a consequence of their different hardiness.

Analysis of Variance↗
PubMed2004

The evaluation of dioxin and dioxin-like contaminants in selected food samples obtained from the Belgian market: comparison of TEQ measurements obtained through the CALUX bioassay with congener specific chemical analyses.

A limited number of different foods were analysed for dioxin-like compounds by the CALUX bioassay which is an in vitro luciferase reporter gene assay measuring chemical activation of the aryl hydrocarbon receptor. Sixty-two milk samples were obtained from a surveillance campaign, 34 meat samples and 34 fishery products were purchased from the Belgian market. Bio-analytical and chemo-analytical dioxin toxicity equivalents (TEQ) values of the same milk samples were compared. Spearman's Rank correlation coefficients of 0.72, 0.67, 0.73 were obtained respectively between CALUX-TEQ and PCDD/F-TEQ, DL-PCB-TEQ and PCDD/F+DL-PCB-TEQ. The bioassay limit of detection was 0.1 pg TEQ from 1 g animal lipid, the limit of quantification was 0.4 pg TEQ. The repeatability of the CALUX bioassay (variability of butter fat samples analysed in the same run) showed a coefficient of variation (CV) of 10%, intra laboratory reproducibility based on independent runs of the same butter fat samples showed more variation (CV of 26% for samples above 2 pg TEQ/g lipid). All milk samples with a chemical TEQ value above the current limit value in Belgium showed an elevated CALUX-TEQ concentration, above 6 pg TEQ/g lipid. No false negative results were obtained. Based on the good correlation between CALUX-TEQ and chemically measured TEQ levels, the CALUX bioassay can be recommended as a screening tool for routine measurement of potentially toxic PHAHs in milk samples. Chemical analyses could then largely be restricted to positive samples, in order to identify the nature and to quantify the concentration of the chemicals that give the positive signal. Meat samples showed lower CALUX-TEQ values per gram lipid compared to fish samples. The fish samples showed a wider range of CALUX-TEQ values than the meat samples.

Belgium↗
PubMed1999

An effective, rapid and simple method for isolation of Shiga toxin-producing Escherichia coli O26, O111 and O157 from faeces and food samples.

An effective, rapid and simple method was developed for isolating Shiga toxin-producing Escherichia coli (STEC) O26:H11, O111:H- and O157:H7 from faeces and food in less than 24 h. The procedure involves enrichment of these samples in Trypticase soy broth (TSB) at 42 degrees C for 6 h. The enrichment culture is exposed to 1/8N HCl +0.5% NaCl solution (1 + 1) for 30 sec, then plated onto MacConkey agar containing sorbitol, tellurite and cefixime (CT-SMAC) following culture at 37 degrees C for 18 h. The findings were compared with conventional enrichment methods for efficiency in recovering STEC from bovine faeces. The new method increased the sensitivity for isolation of < 10(2) STEC O26:H11, O111:HUT and O157:H7 CFU/g of bovine faeces and decreased the growth of other gram-negative microorganisms. This procedure is readily implemented for use in laboratories doing routine microbiological testing.

Animals↗
PubMed2005

Detection of pathogenic bacteria in food samples using highly-dispersed carbon particles.

There is an unmet need for detection methods that can rapidly and sensitively detect food borne pathogens. A flow through immunoassay system utilizing highly dispersed carbon particles and an amperometric technique has been developed and optimized. A sandwich immunoassay format was utilized in which pathogenic cells were captured by antibodies immobilized onto activated carbon particles, and labeled with horseradish peroxidase (HRP) conjugated antibodies. Flow of the peroxidase substrates resulted in an amperometric signal that is proportional to the number of captured cells. Factors influencing the analytical performance of the system, such as the quantity of carbon particles and concentrations of capture antibody, enzyme labeled antibody, and enzyme substrates, were investigated and optimized. Detection and quantification of Escherichia coli, Listeria monocytogenes and Campylobacter jejuni were demonstrated with low detection limits of 50, 10, and 50 cells/ml, respectively, and an overall assay time of 30 min. Milk and chicken extract samples were spiked with various concentrations of these pathogens and were used to challenge the system. The system design is flexible enough to allow its application to the detection of viruses and proteins.

Bacteria↗
PubMedDate not supplied

Phage types of Salmonella enteritidis isolated from clinical and food samples, and from broiler carcasses in southern Brazil.

272 isolates of Salmonella Enteritidis (111 isolated from frozen broiler chicken carcasses, 126 from human food and other biological materials involved in food poisoning outbreaks and 35 from different poultry materials) were selected for phage typing. From these, 111 were phage typed, 57.65% being classified as phage type 4, 32.43% as phage type 4a, 3.60% as phage type 6a and 0.90% as phage type 7, whereas 5.40% samples were not phage typeable. The predominance of phage type 4 is in agreement with the results published worldwide, and reinforces the need for studies related to the epidemiological meaning of these findings.

Animals↗
PubMed1990

Supercritical fluid extraction and chromatography of cholesterol in food samples.

A method based on supercritical fluid chromatography is presented which can be used for the determination of cholesterol in certain foods. The method involves the extraction with supercritical carbon dioxide and analysis of the extracts using a capillary column with supercritical carbon dioxide as mobile phase and flame ionization detection. Quantification is achieved using cholesteryl chloroacetate as an internal standard.

Carbon Dioxide↗
PubMed2002

Cross contamination of lead and cadmium during dry ashing of food samples.

Common white sugar was ashed in a muffle furnace under controlled heating at 450 degrees C. Together with these samples, sugar with added amounts of Pb and Cd (20, 50 micro g) was mineralized in the same furnace. Depending on the absolute amount of Pb and Cd present in the furnace, an increase in the 'blank' values of the unspiked sugar samples was found. The same effect was observed when reference material containing natural amounts of Pb and Cd (TORT-1, Lobster) was present in the furnace. Although the results strongly depend on the blank levels of the muffle furnace, cross contamination effects could be demonstrated for both elements. The investigations demonstrate, that at a temperature of 450 degrees C, both Cd and Pb are lost during ashing of samples. The type of matrix in a sample with high contents of Pb and Cd has no significant effect on the volatility of these elements. The vapor lost from a sample containing high amounts of Pb and Cd will falsify the concentration in low level samples present in the furnace.

Calcium↗
PubMed2001

Enterotoxin production and DNA fingerprinting in Staphylococcus aureus isolated from human and food samples. Relations between genetic types and enterotoxins.

A total of 224 Staphylococcus aureus strains from human carriers (110 strains) and manually handled foods (114 strains) collected in the Principality of Asturias, Spain over 1995-1999 were analysed for the production of enterotoxins (SEs) A, B, C, and D by a reversed passive latex agglutination test and by amplification of ent genes (A, B, C, D, E, and J) using PCR. Sixty-two strains were enterotoxigenic and a good relation between detection of SEs and their ent genes was found. No strain carried entE and all strains producing SED carried entD and entJ genes. Among the enterotoxigenic strains the percentages registered were 29, 8, 35, 18, 2, 2, and 6 for SEA, SEB, SEC, SEDJ, SEAC, SEADJ and SECDJ, respectively. DNA fingerprinting of 77 strains (the SE prototypes, 62 enterotoxigenic and 10 non-enterotoxigenic [NE]) was carried out by randomly amplified polymorphic DNA using two selected primers independently. Combining results from both primers, 10 genetic types were defined, which showed a different degree of relationship (similarity coefficient: 0.9-0.36) and were clustered into three lineages. One lineage clustered five genetic types and a wide diversity of strains, mainly SEA, SEB, SEDJ, and NE. Another lineage clustered only SEC, SECDJ and NE strains. These two lineages showed a low genetic relationship and appeared as endemic in healthy humans living in the Principality of Asturias. The third lineage included only the prototype strains for SEA and SEE.

Bacteriological Techniques↗