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PubMed2005

Inhibition of toxicogenic Bacillus cereus in rice-based foods by enterocin AS-48.

The antimicrobial effect of the broad-spectrum bacteriocin enterocin AS-48 against the toxicogenic psychrotrophic strain Bacillus cereus LWL1 has been investigated in a model food system consisting of boiled rice and in a commercial infant rice-based gruel dissolved in whole milk stored at temperatures of 37 degrees C, 15 degrees C and 6 degrees C. In food samples supplemented with enterocin AS-48 (in a concentration range of 20-35 mug/ml), viable cell counts decreased rapidly over incubation time, depending on the bacteriocin concentration, the temperature of incubation and the food sample. Enterotoxin production at 37 degrees C was also inhibited. Heat sensitivity of endospores increased markedly in food samples supplemented with enterocin AS-48: inactivation of endospores was achieved by heating for 1 min at 90 degrees C in boiled rice or at 95 degrees C in rice-based gruel. Activity of enterocin AS-48 in rice gruel was potentiated by sodium lactate in a concentration-dependent way.

Bacillus cereus↗

PubMed2003

Homogeneity check of agricultural and food industries samples using near infrared spectroscopy.

Samples distributed in proficiency testing schemes (PTS) need to be homogeneous in order to be sure that if a laboratory has a result different from the other laboratories, its error can be attributed to its analysis method and not to its sample. This control must be done according to the ISO 13528 draft standard before sending the samples to the laboratories. It can be done by determining homogeneity targets by sub-contracting to accredited laboratories using reference methods, but this engenders logistic and financial problems. That is why a homogeneity check using Near Infrared Spectroscopy (NIR) has been developed for agricultural and food industries samples prepared for PTS at Bipea (Bureau Interprofessionnel d'Etudes Analytiques). To evaluate the homogeneity among samples, this procedure involves a comparison of NIR spectra, the determination of global homogeneity criteria and the use of control charts. The method of control developed and carried out at Bipea allows the rapid and easy monitoring of the performance of the sample preparation.

Crops, Agricultural↗

PubMed2001

Intake of dioxins and related compounds from food in the U.S. population.

The first U.S. nationwide food sampling with measurement of dioxins, dibenzofurans, and coplanar, mono-ortho and di-ortho polychlorinated biphenyls (PCBs) is reported in this study. Twelve separate analyses were conducted on 110 food samples divided into pooled lots by category. The samples were purchased in 1995 in supermarkets in Atlanta, GA, Binghamton, NY, Chicago, IL, Louisville, KY, and San Diego, CA. Human milk also was collected to estimate nursing infants' consumption. The food category with highest World Health Organization (WHO) dioxin toxic equivalent (TEQ) concentration was farm-grown freshwater fish fillet with 1.7 pg/g, or parts per trillion (ppt), wet, or whole, weight. The category with the lowest TEQ level was a simulated vegandiet, with 0.09 ppt. TEQ concentrations in ocean fish, beef, chicken, pork, sandwich meat, eggs, cheese, and ice cream, as well as human milk, were in the range O.33 to 0.51 ppt, wet weight. In whole dairy milk TEQ was 0.16 ppt, and in butter 1.1 ppt. Mean daily intake of TEQ for U.S. breast-fed infants during the first year of life was estimated at 42 pg/kg body weight. For children aged 1-11 yr the estimated daily TEQ intake was 6.2 pg/kg body weight. For males and females aged 12-19 yr, the estimated TEQ intake was 3.5 and 2.7 pg/kg body weight, respectively. For adult men and women aged 20-79 yr, estimated mean daily TEQ intakes were 2.4 and 2.2 pg/kg body weight, respectively. Estimated mean daily intake of TEQ declined with age to a low of 1.9 pg/kg body weight at age 80 yr and older. For all ages except 80 yr and over, estimates were higher for males than females. For adults, dioxins, dibenzofurans, and PCBs contributed 42%, 30%, and 28% of dietary TEQ intake, respectively. DDE was also analyzed in the pooled food samples.

Adolescent↗

PubMed2002

Effects of soy sauce and sugar on the formation of heterocyclic amines in marinated foods.

The effects of soy sauce and sugar on the formation of heterocyclic amines (HAs) in marinated pork, eggs, and bean cakes were studied. Food samples were immersed in water in the presence of various levels of soy sauce and sugar, and the mixtures were subjected to simmering at 98+/-2 degrees C for 1 h in a closed saucepan. The various HAs in marinated food samples were analyzed by HPLC with photodiode-array detection. Results showed that seven HAs: 2-amino-3-methylimidazo[4,5-f]quinoline (IQ); 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx); 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ); 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx); 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1); 2-amino-1-methyl-6-phenylimidazo[4,5-f]pyridine (PhIP); and 2-amino-9H-pyrido[2,3,-b]indole (AalphaC) were detected in marinated pork, while five HAs: IQ, MeIQx; 4,8-DiMeIQx; PhIP; and AalphaC in bean cakes, as well as four HAs, MeIQx, 4,8-DiMeIQx, Trp-P-1 and PhIP in eggs. In most samples PhIP was formed in largest amount, followed by MeIQx, 4,8-DiMeIQx, IQ, AalphaC, Trp-P-1 and MeIQ. The amounts of HAs produced in marinated food samples followed an increased order for each increasing level of soy sauce or sugar. Marinated juice was found to contain a higher content of HAs than marinated foods.

Amines↗

PubMed2004

An analytical device for on-site immunoassay. Demonstration of its applicability in semiquantitative detection of aflatoxin B1 in a batch of samples with ultrahigh sensitivity.

A simple analytical device has been developed for performing noninstrumental immunofiltration-based assay on a batch of samples. The device consists of membrane strips, with antibody-immobilized zones, attached to a polyethylene card. A moist filter paper placed between the membrane and the polyethylene card acts as the absorbent body. The device was used to estimate very low concentrations of aflatoxin B1 (AFB1) present in food samples by using an improved catalyzed reporter deposition (Super-CARD) method of signal amplification involving biotinylated tyramine (B-T) and avidin-horseradish peroxidase conjugate. 4-chloro-1-naphthol was used as the substrate for visualization. Semiquantitative results are obtained by visual comparison of the color intensity (inversely related to the analyte concentration) of a sample spot with those of reference standards. Quantitative estimation is possible by densitometric analysis (detection limit 0.25 pg/spot, 0.01 ng mL(-1)). Dilute samples can be assayed by in situ concentration with improved dose-response characteristics. A batch of 12 extracted samples can be analyzed in a single test card within 12 min. Spiked and contaminated samples of groundnut, corn, wheat, cheese, and chilli were analyzed without sample cleanup. The matrix interferences were eliminated by using appropriate dilution of the aqueous methanol extracts. Mean recoveries from different food samples were between 91 and 104%. The values obtained for infected corn and groundnut samples correlated well (R2=0.99) with the estimates by HPLC. The method is well-suited for visual screening of agricultural and food samples for AFB1 under field conditions.

Aflatoxin B1↗

PubMed1989

Biotin assessment in foods and body fluids by a protein binding assay (PBA).

The biotin content of plant and animal food samples as well as of human plasma and urine specimens was assessed by a modified protein binding assay (PBA). Protein bound biotin in samples was released by digestion with papain, food samples were in addition treated previously with liquid nitrogen. Comparing analyses by use of the conventional microbiological test with L. plantarum resulted in slightly enhanced biotin values, in case of plasma by 9.2% and in case of urine by 10.3%, but the results obtained by both methods correlated well (r = 0.926 for plasma and 0.934 for urine). Regarding food analysis the additional comparison of different disintegration procedures led to best reproducible results by using the PBA with preceding papain digestion.

Adult↗

PubMedDate not supplied

Evaluation of a dry, rehydratable film method for rapid enumeration of Staphylococcus aureus.

Results with the new 3M Petrifilm Rapid S. aureus Count (RSA) Plate method were compared with those of the classical Baird-Parker agar (BPA) method for detection and enumeration of Staphylococcus aureus. Studies on 219 bacterial strains demonstrated that the Petrifilm RSA plate is more sensitive than and as specific as the classical BPA method for confirmed identification of S. aureus. Counts of colonies from 71 pure cultures, 61 naturally contaminated food samples, and more than 750 artificially inoculated food samples showed that the Petrifilm RSA method was as effective as the classical BPA method for identification and enumeration of S. aureus. The Petrifilm RSA method gave results in one-third the time required for the classical method.

Algorithms↗

PubMed1987

Changes in enterococcal population during storage of reconstituted infant food.

A six-fold increase in the enterococcal population was observed in reconstituted infant food samples after storage for 2 h at 37 degrees C. The increase in enterococcal counts at 40 degrees C and 45 degrees C was approximately five-fold during the same period. However, the corresponding total viable counts increased by twelve fold at these temperatures after 2 h. After 12 h, the enterococcal and total viable counts increased to 39 x 10(4) and 36 X 10(7) colony forming units per ml, at 37 degrees C respectively. A similar pattern in enterococcal and total bacterial count was observed at 40 degrees and 45 degrees C. TNase was detected in reconstituted infant food samples held at 37 degrees, 40 degrees and 45 degrees C, after 12 h, while pH values declined to 5.0, 5.1 and 5.2, respectively at the above temperatures. From TNase positive samples, an isolate S. faecium IF-100 capable to produce TNase was recovered. Storage of reconstituted infant food samples in the refrigerator (5 degrees C) resulted in a gradual increase in enterococcal population which reached 39 X 10(3) c.f.u. per ml after 12 days. However, TNase was not detected in any of these samples.

Food Handling↗

PubMed2001

Comparative evaluation of different chromogenic/fluorogenic media for detecting Escherichia coli O157:H7 in food.

Escherichia coli O157:H7 is a serious and common human pathogen that can cause diarrhoea, haemorrhagic colitis, and haemolytic uraemic syndrome (HUS). This study evaluated the enrichment, detection and confirmation procedures for the isolation of E. coli O157:H7 from raw ground beef and raw drinking milk. The purpose of this investigation was to compare Rainbow Agar O157 (RB; Biolog, Hayward, USA), Biosynth Culture Medium O157:H7 (BCM O157:H7; Biosynth, Staad, Switzerland) and Fluorocult HC (HC; Merck, Darmstadt, Germany) with the conventional Sorbitol MacConkey Agar (SMAC, Merck) using mEC + n (raw ground beef) and mTSB + n (raw milk) enrichment media. Single-path GLISA test (Gold Labeled Immuno Sorbent Assay; Merck) was used as the confirmation test. Growth of 466 strains of gram-negative rods isolated from food samples and 46 known E. coli strains from type culture and other collections (34 E. coli O157:H7 strains and 12 serotypes other than E. coli O157:H7) was examined on the agar media. The E. coli O157:H7 strains could readily be isolated and recognized uniquely by their typical black/grey colonies on RB and blue/black colonies on BCM O157:H7. Examination of the 46 known strains of E. coli reference strains showed false negative results on BCM O157:H7 (3.0%), RB (8.8%), HC (5.9%) and SMAC (5.9%) agars. On BCM O157:H7 no false negative results were found with the typical E. coli O157:H7 (beta-D-glucuronidase and sorbitol negative strains). One of two atypical E. coli O157:H7 strains (beta-D-glucuronidase positive) showed similar colouration to the typical strains and was mis-identified by each of the three media (RB, BCM O157:H7, and SMAC agar media). None of the 60 food samples tested yielded E. coli O157:H7. Examination of the food samples, showed that RB gave the lowest number of false positives. The percentages were RB (2.1%), BCM O157:H7 (3.3%), HC (6.2%), and SMAC (57.3%).

Animals↗

PubMed1998

Screening of gluten avenins in foods by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

The first procedure capable of analysing gluten avenins in gluten-free food samples aimed at the diet control of coeliac patients is described. The method is based on the direct observation of the characteristic avenin mass pattern, around 20-30 kDa, as revealed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI/TOF-MS). The mass range where avenin signals appear is free from mass peaks arising from wheat gliadin, barley hordein and rye secalin protein components, which are also toxic to coeliac patients. Therefore, avenins can easily be screened in complex formula food samples elaborated with mixtures of wheat, barley, rye and oats. In addition, a procedure to quantify avenins in food samples is described on the basis of avenin mass area measurement with a detection limit of 0.4 mg of avenins per 100 g of food.

Avena↗

PubMedDate not supplied

[Food poisoning outbreak due to the consumption of spaghetti a la carbonara caused by Salmonella enteritidis].

INTRODUCTION: This paper reports a clinico-epidemiological and microbiological investigation conducted into an outbreak of gastrointestinal infection due to Salmonella enteritidis, where the most likely food vehicle was spaghetti a la carbonara. METHODS: An historic cohort study was conducted out among persons exposed to menus at a school canteen. Data were gathered on age, sex, foods consumed and clinical symptoms. School premises and menus were inspected, food samples obtained (spaghetti and meat balls), and stool samples taken from 30 affected subjects and 8 food handlers. Isolated strains were studied using pulsed-field electrophoresis. Attack rates were computed, and the odds ratio adjusted for the remaining foodstuffs (ORa) used to calculate the independent contribution made by the respective foods to risk of infection. RESULTS: Study coverage was 75.7% (140/185). The overall attack rate was 72.1% (101/140), with 12.9% of those affected requiring hospitalisation. The multivariate analysis showed that, while the spaghetti maintained its association (ORa = 8.4; 95% CI 1.4-51.8), the meat balls registered a reduction in risk (ORa = 1.8; 95% CI 0.4-7.5). S. enteritidis was isolated in stool cultures from 28 affected subjects, and in 2 blood and 6 stool cultures from food handlers (5 of whom were classed as cases). Moreover, S. enteritidis was also isolated in the food samples. On pulsed-field electrophoresis, the strains registered the same electrophoresis pattern. CONCLUSIONS: This outbreak serves to underscore the gravity of Salmonella spp. food poisoning, the danger of using inadequately cooked eggs, and the importance of interviewing food handlers to ensure proper classification (i.e., as patients or carriers). Existing recommendations as to the use of pasteurised egg products ought to be extended in scope.

Adult↗

PubMed2005

Mechanistic study of membrane concentration and recovery of Listeria monocytogenes.

Detection of the foodborne pathogen Listeria monocytogenes requires that food samples be processed to remove proteins and lipids, concentrate microorganisms to a detectable concentration, and recover the concentrated cells in a small volume compatible with micron-scale biochips. Mechanistic considerations addressed in this research include the roles of membrane structure, pore size, and detergents in maximizing recovery of cells from a complex biological fluid. The fluid in this case was a food sample (hotdog extract) inoculated with L. monocytogenes. This study showed how membrane filtration using a syringe filter is able to concentrate L. monocytogenes by 95x with up to 95% recovery of living microorganisms by concentrating 50 mL of food sample into a volume of 500 microL. Tween 20 was added to the sample to prevent irreversible adsorption of the microorganism to the membrane and thereby help to ensure high recovery. Comparison of polycarbonate, mixed cellulose, nylon, and PVDF membranes with 0.2 to 0.45 microm pores showed the 0.2 microm polycarbonate membrane with straight through, mono-radial pores gives the highest recovery of living microorganisms. The mixed cellulose, nylon, and PVDF membranes have a fibrous structure whose characteristic openings are much larger than their effective pore size cut-offs of 0.22 or 0.45 microm. We define conditions for rapid membrane-based cell concentration and recovery that has the potential to supplant enrichment steps that require a day or more. This approach has the added benefit of facilitating examination of a large amount of fluid volume by reducing its volume to a range that is compatible with the microliter scales of biochip or other biosensor detection systems.

Filtration↗

PubMed2001

An analytical method for the rapid screening of organophosphate pesticides in human biological samples and foodstuffs.

Gas chromatography with nitrogen/phosphorus sensitive detection (GC/PND) and electron impact mass spectrometry (GC/MS) with selected ion monitoring provides a simple, rapid and sensitive method for the determination of organophosphate pesticides (OPs). A selective single-step extraction of 23 different OPs in urine, blood, serum and food samples (baby food, soft drinks and instant soups suspected of contamination from a blackmailing scare) is described. The OPs were extracted with 1ml toluene (with and without addition of mevinphos as internal standard), using a 0.7ml aliquot of urine, blood or serum sample. Food samples (0.2g) were homogenised with water (0.5ml) before extraction. An amount of 1microl of the toluene phase (extraction supernatant) was analysed directly by GC/PND and GC/MS.The method was validated using spiked human serum. The OPs were mixed with serum containing 10mg/ml disodium ethane diamine tetraacetic acid disodium salt (EDTA disodium salt) and stored up to 10 days at 4 and -20 degrees C, respectively. The recovery rates of OPs in freshly spiked human plasma ranged between 50% (dimethoate) and 133% (dialifos). OPs in plasma proved to be stable at -20 degrees C. Their levels decreased only slightly after storage at 4 degrees C.

Animals↗

PubMed2000

[Detection of Escherichia coli strains harboring pathogenicity island of Yersinia enterolitica in diarrheal patients and animals in China].

OBJECTIVE: To investigate the prevalence of Escherichia coil strains harboring high pathogenicity island of Yersinia enterocolitica in diarrhea patients, animals, food samples and resulted clinical symptoms. METHODS: Colony hybridization, DNA dot hybridization and polymerase chain reaction (PCR) were used. RESULTS: HPI - harboring E. coli were found in the strains isolated in various provinces of China. The isolation rates were 27.05% (436/1,612) in the strains isolated from diarrhea patients, 10.23% (9/88) in the strains isolated from food samples and 5.71% (16/280) in the strains isolated from feces of cattle and pigs. Typical clinical symptoms of diarrhea caused by HPI - harboring E, coli were inappetency, abdominal pain, shiver and vapidity. Patient's temperature was usually normal or low. Over six episodes of diarrhea was frequently observed, of which most were unformed stools with mucous. CONCLUSION: E. coli strains harboring high - pathogenicity - island of Yersinia species were frequently isolated from diarrhea patients, animals and food samples as well, which might be one of the major causes of diarrhea in China.

Animals↗

PubMed1985

Rapid detection of salmonellae by immunoassays with titanous hydroxide as the solid phase.

Radioimmunometric and enzyme-immunometric assays were developed for the detection of salmonellae in pure and mixed cultures as well as in 59 food samples. The performances of titanous hydroxide suspension and microtiter plates as the solid phase for the immobilization of microorganisms were compared in these immunoassays. Detection of populations of salmonella cells in pure culture, diluted with saline, was 4- to 10-fold more sensitive with the microtiter plates. However, with mixed culture of salmonella and other enterobacterial species, the detection sensitivity with titanous hydroxide was 100- to 160-fold more sensitive than with microtiter plates. Good correlation existed between results of a standard cultural method for the detection of salmonellae in foods and those obtained from radioimmunometric and enzyme-immunometric assays utilizing titanous hydroxide. However, a high incidence of false-positive and false-negative results with food samples occurred with the enzyme-immunometric assay utilizing microtiter plates. The results provided strong evidence for the merits of substituting titanous hydroxide for microtiter plates as the solid phase for the immobilization of salmonellae for their detection by immunoassays. The immunoassays were rapid and enabled the analysis of a large number of selective enrichment cultures of food samples for salmonellae within 8 h.

False Negative Reactions↗

PubMed1997

High-performance liquid chromatography-electrospray ionisation-tandem mass spectrometry for the analysis of 1,2,3,4-tetrahydro-beta-carboline derivatives.

A rapid and sensitive method is described for the detection of 1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid, 1-methyl-1,2,3,4- tetrahydro-beta-carboline-3-carboxylic acid and 1-methyl-1,2,3,4-tetrahydro-beta-carboline by electrospray ionization tandem mass spectrometry coupled to liquid chromatography. In combination with selected reaction monitoring (SRM) detection limits of 3 ng ml-1 (ca. 75 fmol on column) were established by the use of model solutions. Due to the excellent selectivity and sensitivity of SRM no sample preparation step was required prior to analysis of food samples. In addition, any artifactual formation of tetrahydro-beta-carbolines could be excluded. Application of the method revealed that all food samples analyzed contained both tetrahydro-beta-carboline-carboxylic acids at ng ml-1 to microgram ml-1 concentrations, whereas 1-methyl-1,2,3,4-tetrahydro- beta-carboline was identified in most samples as a minor constituent.

Alkaloids↗

PubMed1996

Tyramine content of previously restricted foods in monoamine oxidase inhibitor diets.

Traditional monoamine oxidase inhibitors (MAOIs) remain an important class of drugs for a variety of psychiatric conditions, including depressive illnesses, anxiety, and eating disorders. It was the objective of this study to refine the MAOI diet by determining the tyramine content of a variety of untested and "controversial" foods that continue to appear on MAOI diet-restricted food lists. A secondary objective of the study was to evaluate the effect of freshness on the tyramine content of some foods. Fifty-one food samples were evaluated for tyramine content by liquid chromatography. Food samples included a selection of sausages, beverages, sliced meat products, including chicken liver, and some fruits, including raspberries, bananas, and banana peels. Foods that were found to have dangerously high concentrations of tyramine (> or = 6 mg/serving) included chicken liver aged 9 days (63.84 mg/30 g), air-dried sausage (7.56 g/30 g), soy sauce (0.941 mg/ml), and sauerkraut (7.75 mg/250 g). Of the foods analyzed in this study, only those with high tyramine content per serving should continue to be absolutely restricted. All other foods are either safe for consumption or safe in moderation. The data provided should be combined with the data from other similar analytical studies to develop a list of foods that should be absolutely restricted. A more accurate list of restricted foods may enhance patient dietary compliance.

Diet Therapy↗

PubMed1997

Preparation of PCR samples from food by a rapid and simple centrifugation technique evaluated by detection of Escherichia coli O157:H7.

A sample treatment method based on buoyant density centrifugation which separates bacteria from food, concentrates bacteria and removes PCR inhibitors is described. The method involves a one minute centrifugation of food homogenate layered over a gradient medium (Percoll or BacXtractorTM) in Eppendorf tubes, followed by a single wash step. The small scale of this treatment makes it possible to process many samples in a short time. To evaluate the method beef and minced beef samples, spiked with strains of Escherichia coli O157:H7, were treated and then analysed by PCR aimed at verocytotoxin- (VT1 and VT2) and eae-genes. The detection limits in 1:10 (w/v) beef and minced beef homogenates were 125-250 cfu ml-1 (1250-2500 cfu g-1) and 1000 cfu ml-1 (1 x 10(4) cfu g-1), respectively. The enrichment of spiked samples in buffered peptone water at 37 degrees C for 6 hours before buoyant density centrifugation and PCR, allowed 0.5 cfu g-1 beef and 5 cfu g-1 minced beef to be detected. This combination of enrichment and buoyant density centrifugation was also used for analysis of 43 beef samples from a consignment in which E. coli O157:H7 had been detected, and detected VT-genes in all 43 samples. E. coli O157:H7 was also separated and detected in spiked samples of milk, lettuce, shrimps, and blue cheese at arbitrary concentrations of 3000 cfu ml-1. The present sample preparation method has the potential to be applicable to many other combinations of bacteria and food, and in connection with other detection methods than PCR as well.

Centrifugation, Density Gradient↗