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1.
A second generation nucleic acid hybridization assay has been developed and evaluated against the conventional culture method for detection of salmonellae in foods. The assay involves a liquid hybridization with Salmonella-specific oligonucleotide probes, capture of probe:target hybrids onto a solid support (plastic dipstick), and a colorimetric end point detection. The assay can be completed in 2.5 h, following approximately 44 h of culture enrichment. One thousand samples representing 20 food types were analyzed in parallel by both methods. Samples included uninoculated test product, and product inoculated with Salmonella at 2 levels. Eighteen Salmonella serotypes were used as inocula. The data demonstrate that the colorimetric hybridization method and the conventional culture method are equivalent in their ability to detect Salmonella contamination of foods.  相似文献   

2.
A collaborative study was performed in 11 laboratories to validate a colorimetric DNA hybridization (DNAH) method for rapid detection of Salmonella in foods. The method was compared to the standard culture method for detection of Salmonella in nonfat dry milk, milk chocolate, soy isolate, dried whole egg, ground black pepper, and raw ground turkey. Samples inoculated with high (0.4-2 cells/g) and low (0.04-0.2 cells/g) levels of Salmonella and uninoculated control samples were included in each food group analyzed. There was no significant difference in the proportion of samples positive by DNAH and culture procedure for any of the 6 foods. The colorimetric DNA hybridization assay screening method has been adopted official first action as a rapid screening method for detection of Salmonella in all foods.  相似文献   

3.
The efficiency of 2 commercial enzyme-linked immunosorbent assay (ELISA) kits (Listeria-Tek and Tecra) for detecting Listeria in naturally contaminated foods was evaluated and compared with that of the culture method described in the Bacteriological Analytical Manual (BAM). Both ELISAs use modified University of Vermont (UVM-1) medium as a primary enrichment; the BAM method uses Listeria enrichment broth. Secondary enrichments for Listeria-Tek and Tecra, respectively, were Fraser broth and UVM-2, which contains additional acriflavin-HCl. When ELISA test results differed, secondary enrichments were tested against the other ELISA; Fraser broth was used to determine recovery rates because of its superiority over UVM-2. Of the 178 food samples examined, the presence of Listeria was detected and culturally confirmed in 38, 37, and 40 samples by the BAM, Listeria-Tek, and Tecra methods, respectively. Differences in results of the ELISAs compared with those of the BAM method were not statistically significant; however, differences between results of the 2 ELISA methods were significant. It was concluded that as rapid screening methods, the Listeria-Tek and the Tecra kits qualify as alternative methods to the BAM cultural method.  相似文献   

4.
The presence of Salmonella spp in estuarine waters was investigated along the Patras harbor where pipes containing urban sewage terminate. Salmonellae detection was performed by a conventional culture and a DNA probe technique (Gene-Trak Salmonella assay — Gene Trak Systems, Framingham). The Gene Trak colorimetric Salmonella assay uses the ribosomal hybridization format followed by a colorimetric detection system. Salmonellae were detected in 3 out of 102 water samples (2.9%) when the culture technique was used and in 7 out of 102 samples (6.8%) when the DNA probe technique was used . All DNA probe positive samples were confirmed by culture of the pre-enrichment Gram-negative broth and biochemical tests according to the manufacturers instructions. Culture positive samples were confirmed by serological tests in the National Salmonella-Shigella Center (National Institute of Public Health). The data demonstrate that the colorimetric hybridization method and the conventional culture method are equivalent in their ability to detect Salmonellae in estuarine waters (χ2 = 0.33 < 2.43). Both methods have the disadvantage of giving false negative results. However, the Gene Trak assay saves time by lessening the response time in the case of a contamination problem.  相似文献   

5.
A collaborative study was performed in 11 laboratories to validate a DNA hybridization (DNAH) procedure for detection of Salmonella in foods. The DNAH procedure was compared to the standard culture method for detection of Salmonella in 6 foods: ground pepper, soy flour, dry whole egg, milk chocolate, nonfat dry milk, and raw deboned turkey. With the exception of turkey which was naturally contaminated, uninoculated and inoculated samples of each food group were analyzed. Results for the DNAH method were significantly better than for the standard culture method at the 5% probability level for the detection of Salmonella in turkey. There was no significant difference between the methods for the other 5 foods. The method has been adopted official first action.  相似文献   

6.
Direct plating technique for enumeration of Listeria monocytogenes in foods   总被引：2，自引：0，他引：2  
The advantages and disadvantages of various techniques for detecting and enumerating Listeria monocytogenes in foods are reviewed, and results from a study designed to compare 14 direct plating media for their suitability to recover uninjured cells of L. monocytogenes from 4 foods are summarized. McBride Listeria agar (MLA), gum base nalidixic acid tryptone soy agar (GBNTSA), modified Despierres agar (MDA), and modified MLA (MMLA) performed best for recovering all inoculum populations from milk and ice cream mix. For Brie cheese, MLA, MDA, MMLA, and Dominguez Rodriguez isolation agar were superior for recovering L. monocytogenes; GBNTSA, MDA, MMLA, and Donnelly's Listeria enrichment agar were best for recovering the organism from cabbage. Direct plating procedures without prior enrichment can be utilized successfully for recovering L. monocytogenes from foods such as pasteurized milk and ice cream mix, which contain low populations of background microflora. However, recovery of L. monocytogenes from foods such as raw cabbage and Brie cheese, which contain high populations of other microorganisms, was not satisfactory using direct plating procedures.  相似文献   

7.
Both lipophilic and hydrophilic antioxidant capacities were determined using the oxygen radical absorbance capacity (ORAC(FL)) assay with fluorescein as the fluorescent probe and 2,2'-azobis(2-amidinopropane) dihydrochloride as a peroxyl radical generator on over 100 different kinds of foods, including fruits, vegetables, nuts, dried fruits, spices, cereals, infant, and other foods. Most of the foods were collected from four different regions and during two different seasons in U.S. markets. Total phenolics of each sample were also measured using the Folin-Ciocalteu reagent. Hydrophilic ORAC(FL) values (H-ORAC(FL)) ranged from 0.87 to 2641 micromol of Trolox equivalents (TE)/g among all of the foods, whereas lipophilic ORAC(FL) values (L-ORAC(FL)) ranged from 0.07 to 1611 micromol of TE/g. Generally, L-ORAC(FL) values were <10% of the H-ORAC(FL) values except for a very few samples. Total antioxidant capacity was calculated by combining L-ORAC(FL) and H-ORAC(FL). Differences of ORAC(FL) values in fruits and vegetables from different seasons and regions were relatively large for some foods but could not be analyzed in detail because of the sampling scheme. Two different processing methods, cooking and peeling, were used on selected foods to evaluate the impact of processing on ORAC(FL). The data demonstrated that processing can have significant effects on ORAC(FL). Considering all of the foods analyzed, the relationship between TP and H-ORAC(FL) showed a very weak correlation. Total hydrophilic and lipophilic antioxidant capacity intakes were calculated to be 5558 and 166 micromol of TE/day, respectively, on the basis of data from the USDA Continuing Survey of Food Intakes by Individuals (1994-1996).  相似文献   

8.
An accurate, reproducible method for less than or equal to 1 ppm iodine in foods is required for nutritional labeling. In order to ascertain the current status of iodine analysis in foods, 7 samples, representing different food classes, were analyzed by 8 laboratories. Six laboratories used their modifications of the Ce-As-I catalytic method preceded by alkaline dry ashing. Two laboratories used neutron activation analysis (NAA), with differing radiochemical separations. The study showed wide discrepancy in analytical results. Mean relative standard deviation for all laboratories was 77.9% between laboratories; 19.1% within-laboratories. Laboratories using NAA had only slightly better precision than did laboratories using the chemical method. The lowest level reported on the entire group of samples ranged among laboratories from 0.0089 to 0.65 ppm. Figures reported by a laboratory are, in general, consistently high or consistently low. The only differences in methodology which may possibly correlate with level of iodine obtained are the use of NAA technique and use of manual, rather than automated, colorimetry.  相似文献   

9.
Furan and acrylamide are two possible carcinogens commonly found in many thermally processed foods. The possibility of using ionizing radiation to reduce the levels of thermally induced furan and acrylamide in water and selected foods was investigated. Aqueous furan solutions, and foods (frankfurters, sausages, infant sweet potatoes) that contained furan were irradiated to various doses of gamma-rays. Water and oil spiked with acrylamide and potato chips (a known acrylamide-containing food) were also irradiated. In addition, possible irradiation-induced formation of acrylamide in glucose and asparagine solutions was analyzed. Results showed that irradiation at 1.0 kGy destroyed almost all furan in water. In frankfurters, sausages, and infant sweet potatoes, the rate of irradiation-induced destruction of furan was much lower than the rate in water, although significant reductions in furan levels were observed in all foods. Irradiation at 2.5-3.5 kGy, doses that can inactivate 5-log of most common pathogens, reduced furan levels in the food samples by 25-40%. Similarly to furan, acrylamide in water was also sensitive to irradiation. After 1.5 kGy of irradiation, most of the acrylamide was degraded. Irradiation, however, had a very limited effect on acrylamide levels in oil and in potato chips, even at a dose of 10 kGy. No detectable acrylamide was formed in the mixture of asparagine and glucose upon irradiation. These results suggest that a low dose of irradiation easily destroys furan and acrylamide in water. In real foods, however, the reduction of furan was less effective than in water, whereas the reduction in acrylamide was minimal.  相似文献   

10.
Several countries have introduced mandatory labeling requirements on foods derived from genetically modified organisms. Real-time quantitative Polymerase Chain Reaction (PCR) has quickly become the method of choice in support of these regulations and requires the development of separate PCR assays targeting the transgenic sequence as well as a specific endogenous gene sequence. To develop a Brassica napus-specific PCR assay, partial sequences of the acetyl-CoA carboxylase BnACCg8 gene from B. napus and the closely related Brassica rapa were determined and compared, and a region of unique nucleotide sequence was identified. Universal amplification primers were designed to either side of this region, and a locked nucleic acid TaqMan probe was designed to the B. napus-specific sequence. Evaluation of this primer/probe combination indicated a high level of specificity to B. napus: no amplification signal was observed with any other species tested, including five closely related Brassica species. The method was assayed with 14 different B. napus cultivars, and comparable amplification curves were consistently obtained for all. The assay was highly sensitive, with a limit of detection between 1 and 10 haploid copies. Practically, the method was demonstrated to be effective for the detection of processed food samples and for the quantification of Roundup Ready canola content in mixed samples.  相似文献   

11.
Lupine flour, protein, and fiber have become common ingredients in food products. The association of lupine-related allergic incidents with peanut allergy is a cause for concern as the latter may bring about severe reactions. In this study, a hybridization probe-based real-time PCR assay for the detection of lupine DNA in foods was developed. Particular attention was paid to the specificity of the method, which was verified by analysis of DNA extracts from more than 50 potential food ingredients such as legumes, cereals, seeds, nuts, spices, fruits, and meat. The limit of detection of the method was determined as 0.1 mg/kg. The successful detection of the presence/absence of lupine DNA in 20 samples proved the suitability of the assay for the analysis of frequently encountered food matrices.  相似文献   

12.
OBJECTIVE: To assess the relationship between education and the intake of a variety of individual foods, as well as groups of foods, for Australian men and women in different age groups. DESIGN: Cross-sectional national survey of free-living men and women. SUBJECTS: A sample of 2501 men and 2739 women aged 18 years and over who completed the National Nutrition Survey (NNS) 1995. METHODS: Information about the frequency of consumption of 88 food items was obtained using a food-frequency questionnaire in a nation-wide nutrition survey. Irregular and regular consumers of foods were identified according to whether they consumed individual foods less than or more than once per month. The relationship between single foods and an index of education (no post-school qualifications, vocational, university) was analysed via contingency table chi-square statistics for men and women. Food group variety scores were derived by assigning individual foods to conventional food group taxonomies, and then summing the dichotomised intake scores for individual foods within each food group. Two-way analyses of variance (education by age groups) were performed on food variety scores for men and women, separately. RESULTS: While university-educated men and women consumed many individual foods more regularly than less-educated people, they were less likely to be regular consumers of several meat products. The relationship between education and food consumption was less apparent when individual food scores were aggregated into food group scores. University-educated men and women exhibited higher scores on total food group variety than the other educational groups. CONCLUSIONS: Higher education is associated with the regular consumption of a wider variety of foods. Aggregation of individual food consumption indices into food variety scores may mask the apparent effects of educational background on food consumption.  相似文献   

13.
Industry perspectives on Listeria monocytogenes   总被引：1，自引：0，他引：1  
Industry concerns and our ongoing research on Listeria are discussed in this report. Topics include sampling for analysis; sanitizers and their use in manufacturing facilities; precautions on use of the FDA method for Listeria; use of the Vitek Gram Positive Identification Card; and a brief discussion on findings of Listeria in environmental samples taken from the same site at the same time of year in 1986 and 1987.  相似文献   

14.
A method was developed specifically to detect naturally occurring Listeria monocytogenes in meat because the traditional cold enrichment procedure was extremely slow and other procedures were ineffective. This method could identify beta-hemolytic Listeria colonies in 3-4 days. The use of a 2-stage enrichment, highly selective LPM agar, and a thin-layer horse blood agar plate for the detection of beta-hemolytic Listeria isolates are the important steps of this method. L. monocytogenes was recovered from 20 of 41 samples of frozen ground beef, 12 of 23 samples of pork sausage, and 7 of 22 samples of poultry. These results indicate that L. monocytogenes is common in raw meat and that this method is effective for its recovery.  相似文献   

15.
Total dietary fiber was determined in Japanese foods by the Prosky-AOAC method. To accomplish the analyses of unsuitable samples, we introduced a few minor modifications to the versions for (i) seaweed and fruits, (ii) cereals, and (iii) fish and meats. These modified methods were used together with the standard method to obtain results with reasonably good relative standard deviation for 231 foods and 21 groups of mixed foods. In this study, dietary fiber was defined so as not to exclude the nondigestible polysaccharide portions of animal foods. A method was proposed which could estimate more accurately the fiber components of animal foods by measuring the "nondigestible protein" of the fiber sample of the fiber sample by the Biuret colorimetric method, instead of the Kjeldahl method, to avoid deducting the values for aminopolysaccharides. In Japanese diets, the amount of fiber obtained from animals foods was less than 5% of the total intake of dietary fiber.  相似文献   

16.
采用通气堆沤对石油烃污染土壤进行生物修复   总被引：20，自引：0，他引：20  
Laboratory simulation studies and a composting pilot study were conducted to evaluate the capacity of three strains of fungi, indigenous fungus Fusarium sp. and Phanerochaete chrysosporium and Coriolus Versicolor, to remediate petroleum-contaminated soils. In laboratory, the fungi were inoculated into a liquidculture medium and the petroleum-contaminated soil samples for incubation of 40 and 50 days 5 respectively. In the 200-day pilot study, nutrient contents and moisture were adjusted and maintained under aerobiccondition in composting units using concrete container (118.5 cm × 65.5 cm × 12.5 cm) designed specially for this study. The laboratory simulation results showed that all the three fungi were effective in degrading petroleum in the liquid culture medium and in the soil. At the end of both the laboratory incubations, the degradation rates by Phanerochaete chrysosporium were the highest, reaching 66% after incubation in liquid culture for 50 days. This was further demonstrated in the composting pilot study where the degradation rate by P. chrysosporium reached 79% within 200 days, higher than those of the other two fungi (53.1% and 46.1%), indicating that P. chrysosporium was the best fungus for bioremediation of soil contaminated with petroleum. Further research is required to increase degradation rate.  相似文献   

17.
Methodology for isolation of Listeria from foods--a Canadian perspective   总被引：4，自引：0，他引：4  
A previously described monoclonal antibody-enzyme immunoassay system for dairy products was examined to determine its potential for detecting Listeria in naturally contaminated ground meats. In addition, a microtiter plate system was developed which has potential in the rapid detection of Listeria species in foods. Experience in Canada with the U.S. Food and Drug Administration procedure for dairy products, the cold enrichment procedure, and the U.S. Department of Agriculture procedure for meats is discussed. Also, the status on attempts to devise improved selective media for the isolation of Listeria species from foods is described.  相似文献   

18.
A rapid diagnostic test for the detection of Listeria in food products has been created. This test, known as Listeria-Tek, uses 2 monoclonal antibodies specific for Listeria in an enzyme-linked immunosorbent assay (ELISA) format. The test requires only 40 h of broth enrichment with no culturing on solid media. It is extremely simple to perform and easy to interpret, and is at least as sensitive and accurate as the best of the culture methods. The test can be used with dairy products, meat products, and environmental samples. The ELISA test is safely performed on the open bench of the laboratory because no live cultures, no radioactivity, no phage, etc., are necessary. There is no need for special licenses or reserved laboratory space, and no waste disposal problems are encountered. If necessary, one technician could easily perform hundreds of assays per day. A printed data sheet is available for permanent records.  相似文献   

19.
The validity of 2 electrothermal atomic absorption spectrometric methods for determination of selenium in foods and diets was tested. By using 0.5% Ni(II) as a matrix modifier to prevent selenium losses during the ashing step, it was shown that selenium can be determined in samples containing greater than or equal to 1 microgram Se/g dry wt without organic extraction. The mean recovery tested, using NBS Bovine Liver, was 98%; recovery of added inorganic selenium in Bovine Liver matrix was 100%. In addition, this method gave values closest to the median value of all participating laboratories using hydride generation AAS or the spectrofluorometric method in a collaborative study on high selenium wheat, flour, and toast samples. For samples with concentrations less than 1 microgram Se/g dry wt, separation of selenium from interfering Fe and P ions by organic extraction was necessary. Using inorganic 75Se in meat and human milk matrixes, an ammonium pyrrolidine dithiocarbamate-methyl isobutyl ketone-extraction system with added Cu(II) as a matrix modifier yielded the best extraction recoveries, 97 and 98%, respectively. Accuracy and precision of the method were tested using several official and unofficial biological standard materials. The mean accuracy was within 4% of the certified or best values of the standard materials and the day-to-day variation was 9%. The Se/Fe or Se/P interference limits proved to be low enough not to affect selenium determinations in practically all foods or diets. The practical detection limit of the method was 3 ng Se/g dry wt for 1.0 g dry wt samples.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

20.
Water and sediment were studied to assess the impact of wastes from an area used for a disposal area of treated petrochemical effluents in Rio Grande do Sul, Brazil. The study was performed using the Daphnia magna (Straus 1820) for chronical evaluations, mutagenesis in Salmonella/microsome assays, and micronuclei induction in cultures of V79 cell to assess genotoxicity. Six sites were defined for chronic and genotoxic tests by micronuclei induction with liquid and sediment samples. Long-term tests were planned in semi-static flow, with microcrustaceans 2 to 26 h old in the beginning of assays. The minimum level of reproduction required to maintain the species was not reached. There are delays for the beginning of the reproductive process. Survival was also affected in some samples. The reproductive responses were more sensitive on identifying environmental quality than the survival rate. The study of mutagenicity by Salmonella/microsome assay made it possible to define the seasonality of the components showing greater frequency in winter. The predominant event was the frameshift mutation in assays with the presence of metabolism. However, the cytotoxic activity, although present in all seasons, was less frequent in winter. The genotoxicity analysis in V79 cells exposed to liquid samples from the area also showed that cytotoxicity was the most frequent event. This may have interfered in the detection of a potential micronuclei induction. The results showed that, even after treatment, effluents disposed on the soil continue with active pollutants interfering in cladoceran’s quality of life, cellular physiology, and DNA integrity.  相似文献   

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