Journal - Association of Official Analytical Chemists最新文献

Many agrochemicals are applied postharvest on fruits and vegetables to extend their lives and preserve quality during storage, transport, and marketing. Persistence and distribution of residues on the edible portions of produce have been reported for citrus fruits, pome fruits, stone fruits, mangos, strawberries, bananas, kiwi fruits, avocados, some minor fruit commodities, and bell peppers and tomatoes. Data on the persistance and residues of the fungicides benomyl, biphenyl, sec-butylamine, captan, carbendazim, dicloran, fosetyl-aluminum, guazatine, imazalli, iprodione, metalaxyl, o-phenylphenol, prochloraz, thiabendazole, thiophanate-methyl, triadimeton, and vinclozolin, the fumigants ethylene dibromide, methyl bromide, and sulfur dioxide, the insecticides dimethoate and fenthion, the antiscald compounds diphenylamine and ethoxyquin, and the growth regulators 2,4-D and daminozide are presented and discussed.

In 1990, under regulatory monitoring, a total of 19,962 samples of domestically produced food from all 50 states and Puerto Rico and imported food from 92 countries were analyzed by FDA for pesticide residues. Of these, 19,146 were surveillance samples, which are collected when there is no suspicion of a pesticide problem. No residues were found in 60% of domestic surveillance samples and in 64% of import surveillance samples. Of the 19,146 surveillance samples, 2.8% were violative. Under the incidence/level aspect of monitoring, 172 samples of fish/shell-fish, 330 samples of whole milk, and 3502 samples of processed foods including baby foods were analyzed for pesticide residues. Findings from these projects were consistent with regulatory monitoring data. The findings of the 1990 Total Diet Study are evidence that actual dietary intakes of pesticides are generally well below the standards established by FAO/WHO and by EPA. The 1990 results are similar to those obtained in earlier years and demonstrate the continuing safety of the food supply relative to pesticide residues.

An enzyme-linked immunosorbent assay (ELISA) screening test (CITE PROBE) was compared to liquid chromatography (LC) for the determination of aflatoxins in naturally contaminated corn samples. The CITE PROBE, with a positive/negative cutoff of 5 ng/g aflatoxin B1, was correct (based on LC results) on 47 of 51 samples. Two of the incorrect responses by the CITE PROBE were false positives on samples containing 4.4 ng/g and 4.1 ng/g aflatoxins by LC. Another incorrect response was a false negative on a sample containing 5.5 ng/g aflatoxins by LC. The fourth incorrect response was a false positive on a sample containing 1.9 ng/g aflatoxins by LC. On the basis of these results, the CITE PROBE was determined to be a reliable screening method for the detection of greater than or equal to 5 ng/g aflatoxins in corn.

A preenrichment procedure and a direct selective enrichment procedure were compared for recovery of Salmonella artificially inoculated into liquid whole egg, egg yolk, and egg albumen. For liquid whole egg and egg yolk, the 2 procedures were comparable. With egg albumen, however, preenrichment in lactose broth gave significantly higher recoveries than did direct selective enrichment in either selenite cystine or tetrathlonate broths. The lactose preenrichment procedure was used to determine the survival of S. enteritidis in egg yolk and egg albumen over a period of 7 days. As shown by most probably number determinations, counts of S. enteritidis inoculated into egg albumen decreased by 3 log units, whereas those in egg yolk did not change significantly. It is recommended, therefore, that only the egg yolk be examined for this pathogen. In a comparison of 5 different preenrichment media (lactose broth, brain heart infusion broth, trypticase soy broth, buffered peptone water, and nutrient broth), lactose broth was somewhat less productive than the other 4 media for the recovery of Salmonella from egg yolks. Trypticase soy broth gave the highest recovery.

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.