Showing papers in "Journal of AOAC International in 1997"
TL;DR: An American Association of Cereal Chemists/AOAC collaborative study was conducted to evaluate the accuracy and reliability of an enzyme assay kit procedure for measurement of total starch in a range of cereal grains and products.
Abstract: An American Association of Cereal Chemists/AOAC collaborative study was conducted to evaluate the accuracy and reliability of an enzyme assay kit procedure for measurement of total starch in a range of cereal grains and products. The flour sample is incubated at 95 degrees C with thermostable alpha-amylase to catalyze the hydrolysis of starch to maltodextrins, the pH of the slurry is adjusted, and the slurry is treated with a highly purified amyloglucosidase to quantitatively hydrolyze the dextrins to glucose. Glucose is measured with glucose oxidase-peroxidase reagent. Thirty-two collaborators were sent 16 homogeneous test samples as 8 blind duplicates. These samples included chicken feed pellets, white bread, green peas, high-amylose maize starch, white wheat flour, wheat starch, oat bran, and spaghetti. All samples were analyzed by the standard procedure as detailed above; 4 samples (high-amylose maize starch and wheat starch) were also analyzed by a method that requires the samples to be cooked first in dimethyl sulfoxide (DMSO). Relative standard deviations for repeatability (RSD(r)) ranged from 2.1 to 3.9%, and relative standard deviations for reproducibility (RSD(R)) ranged from 2.9 to 5.7%. The RSD(R) value for high amylose maize starch analyzed by the standard (non-DMSO) procedure was 5.7%; the value was reduced to 2.9% when the DMSO procedure was used, and the determined starch values increased from 86.9 to 97.2%. The amyloglucosidase-alpha-amylase method for measurement of total starch in cereal products has been adopted first action by AOAC INTERNATIONAL
462 citations
TL;DR: Immunoaffinity columns (IACs) are widely used for cleanup and isolation of mycotoxins extracted from foods and biological fluids, particularly aflatoxins, ochratoxin A, and fumonisins.
Abstract: Immunoaffinity columns (IACs) are widely used for cleanup and isolation of mycotoxins extracted from foods and biological fluids, particularly aflatoxins, ochratoxin A, and fumonisins. The columns are prepared by binding antibodies specific for a given mycotoxin to a specially activated solid-phase support and packing the support suspended in aqueous buffer solution into a cartridge. The mycotoxin in the extract or fluid binds to the antibody, impurities are removed with water or aqueous solution, and then the mycotoxin is desorbed with a miscible solvent such as methanol. Further separation can be performed with IAC, followed by liquid chromatographic (LC) quantitation, either off-line or on-line in an automated system, or by fluorometry. IACs have been used by laboratories that developed the antibodies but are also available commercially for aflatoxins, ochratoxin A, fumonisins, zearalenone, and deoxynivalenol. Among commercial IACs, Aflatest P is used as the cleanup step in an LC method and in a solution fluorometry method for corn, peanuts, and peanut butter that was adopted as an AOAC INTERNATIONAL Official Method after evaluation by an international collaborative study. As part of a fluorometer-based test kit, aflatest P was further certified by the AOAC Research Institute to measure total aflatoxins in 10 grains and grain products. IACs can concentrate the analyte from a large amount of sample, allowing detection limits at low parts-per-trillion levels in some cases (e.g., for aflatoxin M1 and ochratoxin A in liquid food matrixes). Regeneration of IACs for reuse in aflatoxin, ochratoxin A, fumonisin, and zearalenone analyses has been investigated.
168 citations
TL;DR: A liquid chromatographic (LC) method developed to identify the synthetic form of the color additive astaxanthin in salmon, based on differences in the relative ratios of the configurational isomers of astxanthin, which can be used to distinguish between aquacultured and wild salmon.
Abstract: Analytical methods are needed to determine the presence of color additives in fish. We report a liquid chromatographic (LC) method developed to identify the synthetic form of the color additive astaxanthin in salmon, based on differences in the relative ratios of the configurational isomers of astaxanthin. The distributions of configurational isomers of astaxanthin in the flesh of wild Atlantic and wild Pacific salmon are similar, but significantly different from that in aquacultured salmon. Astaxanthin is extracted from the flesh of salmon, passed through a silica gel Sep-Pak cartridge, and analyzed directly by LC on a Pirkle covalent L-leucine column. No derivatization of the astaxanthin is required-an important advantage of our approach, which is a modification of our previously described method. This method can be used to distinguish between aquacultured and wild salmon. The method has general applicability and can also be used to identify astaxanthins derived from other sources such as Phaffia yeast and Haematococcus pluvialis algae.
119 citations
TL;DR: The newly developed ELISA is a reliable and powerful method for mass monitoring of MC levels in environmental water and gives a reliable correlation with LC for analysis of MC in water extracts of natural blooms and cultured cyanobacterlal cells.
Abstract: An enzyme-linked immunosorbent assay (ELISA) was developed for direct quantitation of microcystins (MCs), a group of freshwater cyanobacterlal toxins. An antl-MC monoclonal antibody exhibiting broad cross-reactivity to major MC derivatives was used. The detection limit and linear range of the ELISA standard curve with microcystin-(leucine-arginine) (MCLR), a variant of MCs, were 20 and 20-500 pg/mL, respectively. For analysis of MC released from cyanobacterial cells, water sample filtered through a glass fiber filter was applied directly to ELISA. For analysis of total MC (released MC plus intracellular MC), intracellular toxin was extracted by freeze-thawing twice before filtration. Mean recovery of MCLR added to tap water and toxin-free environmental water was 101%, with a coefficient of variation (CV) of 7.3% at toxin levels of 20-500 pg/mL. Mean recovery of MCLR added to toxin-free cyanobacterial extracts was 93%, with a CV of 12.5% at toxin levels of 50-500 pg/mL. At 20 pg/mL, an increasing matrix effect on assay variance was observed; therefore, both released MC and total MC were measured in the range 50-500 pg/ mL. Comparative studies with a liquid chromatographic (LC) method showed that the ELISA gives a reliable correlation with LC for analysis of MC in water extracts of natural blooms and cultured cyanobacterlal cells (r = 0.98). The ELISA was applied to water samples collected from lakes and ponds in Japan. In 4 of 13 and 12 of 17 samples, 81-800 pg released MC/mL and 64-94 000 pg total MC/mL were detected, respectively. By LC separation followed by the ELISA analysis, the presence of MCLR, microcystin-arginine-arginine, and microcystin-tyrosine-arginine were confirmed in 4 ELISA-positive samples selected randomly. The newly developed ELISA Is a reliable and powerful method for mass monitoring of MC levels in environmental water.
100 citations
TL;DR: The ion exchange chromatographic method for determination of fructans in food and food products has been adopted first action by AOAC INTERNATION (997.08) as discussed by the authors.
Abstract: Nine collaborating laboratories assayed 6 blind duplicate pairs of food samples containing the fructans inulin or oligofructose. The 6 sample pairs ranged from low (4%) to high levels (40%). Following the proposed method, the samples were treated with amyloglucosidase and inulinase enzymes and the released sugars were determined by ion exchange chromatography. Repeatability standard deviation ranged from 2.9 to 5.8%; reproducibility standard deviation ranged from 4.7 to 11.1%. The ion-exchange chromatographic method for determination of fructans in food and food products has been adopted first action by AOAC INTERNATIONAL (997.08).
95 citations
TL;DR: The liquid chromatographic procedure is simple, fast, and reliable, and can be used to study the technological and toxicological implications of biogenic amines in cheeses.
Abstract: A liquid chromatographic (LC) procedure for determining 10 biogenic amines in cheese is described. The method is based on ion-pair chromatography on a reversed-phase column with postcolumn derivatization with o-phthaldialdehyde and fluorometric detection. It allowed simultaneous determination of 10 amines in < 80 min: histamine, tyramine, tryptamine, 2-phenylethylamine, serotonin, agmatine, spermine, spermidine, putrescine, and cadaverine. Linearity for each amine was observed between 0.5 and 6.0 micrograms/mL. Detection limits ranged form 0.004 to 0.009 micrograms/20 microL, and determination limits ranged from 0.066 to 0.149 mg/100 g. Amino acids and other amines did not interfere with determination of biogenic amines. Three extractants--methanol, hydrochloric acid, and trichloroacetic acid--were compared in their efficiency to recover amines from spiked samples. Purification of the cheese extract was required prior to LC to avoid interference from compounds in the cheese matrix. Hydrochloric acid extraction followed by purification with diethyl ether gave best recoveries for all the amines (75.5-112.3%). The method is simple, fast, and reliable. It can be used to study the technological and toxicological implications of biogenic amines in cheeses.
80 citations
TL;DR: A chiral gas chromatographic (GC) method that allows determination of alkaloid patterns and identification of isomerically impure synthetic alkaloids was developed, spurred by reports describing a "thermogenic" effect provided by mixtures of ephedrine, caffeine, and aspirin.
Abstract: Ma Huang is a traditional Chinese medicine derived from the aerial parts of several Ephedra species (Ephedraceae). These plants produce (-)-ephedrine, (+)-pseudoephedrine, (-)-norephedrine, (+)-norpseudoephedrine, (-)-N-methylephedrine, and (+)-N-methylpseudoephedrine. Racemic and (-)-ephedrine, (+)-pseudoephedrine, and (+/-)-norephedrine (phenylpropanolamine) are used clinically in the United States and are largely synthetic in origin. Current interest in Ma Huang is spurred by reports describing a "thermogenic" (calorie burning) effect provided by mixtures of ephedrine, caffeine, and aspirin. Products providing the key thermogenic compounds from natural sources are available as dietary supplements in retail outlets. Reports of potentially unsafe levels of the alkaloids, as well as possible fortification of Ma Huang-containing products with synthetic Ephedra alkaloids, prompted the development of a chiral gas chromatographic (GC) method that allows determination of alkaloid patterns and identification of isomerically impure synthetic alkaloids. Nine products were analyzed on a gamma-cyclodextrin capillary GC column. Identity of the alkaloids was verified by GC/mass spectrometry (MS) and GC/matrix isolation/Fourier transform infrared spectroscopy. No synthetic isomers were found in the dietary supplements analyzed. Three products contained only one of the ephedrine-type alkaloids. One product that listed Ma Huang as an ingredient contained no detectable ephedrine-type alkaloid. In products containing measurable quantities of these compounds, total alkaloid levels ranged from 0.3 to 56 mg/g.
73 citations
TL;DR: Aflatoxins B1, B2, G1, and G2 were determined at parts-per-trillion levels in beer by immunoaffinity column cleanup and reversed-phase liquid chromatography with fluorescence detection after trifluoroacetic acid derivatization and reanalysis indicated that an additional 4 Mexican samples and one Brazilian sample contained aflatoxin B1 at low levels.
Abstract: Aflatoxins B1, B2, G1, and G2 were determined at parts-per-trillion levels in beer by immunoaffinity column cleanup and reversed-phase liquid chromatography (LC) with fluorescence detection after trifluoroacetic acid derivatization. Silanized vials were necessary for the evaporation step in order to obtain good recoveries of aflatoxins from spiked beer samples. Recoveries averaged 90-104%, 94%, 84-87%, and 89% for aflatoxins B1, B2, G1, and G2, respectively, at levels of 9.7-133 ng B1, 46 ng B2, 35-140 ng G1, and 41 ng G2/L. Detection limits were 19-20 ng/L for aflatoxins B1 and G1 and 15-16 ng/L for aflatoxins B2 and G2 (signal-to-noise ratio = 3:1) obtained by using an excitation wavelength of 360 nm; at 340 nm these detection limits were lowered to about 2 ng/L. Analysis of 24 beer samples, the majority from the United States and Mexico, showed natural contamination of one sample of Mexican beer at 49 ng B1/L when determined at 360 nm excitation, but reanalysis of 23 of the samples using 340 nm excitation indicated that an additional 4 Mexican samples and one Brazilian sample contained aflatoxin B1 at low levels (< 10 ng/L).
71 citations
TL;DR: Alternative methods for rapid detection or estimation of groups of (indicator) organisms, pathogenic micro-organisms, bacterial toxins and mycotoxins, and molds are compared.
Abstract: Automated analytical instruments for enumerating indicator organisms and diagnostic test kits for pathogens can be used in food microbiology to screen samples and to replace conventional cultural and confirmation steps. Such methods are now available for rapid detection or estimation of groups of (indicator) organisms, pathogenic micro-organisms, bacterial toxins and mycotoxins, and molds. These alternative methods can be classified by the principles on which they are based: modified conventional methods, instrumental measurement of bacterial metabolism, bioluminescence, immunological techniques, DNA techniques, and combinations of these techniques. To meet user expectations, test kits must be accurate, sensitive, specific, rapid (24 h or less), easy to use, and labor-saving. They must also offer the possibility of computerization, a low detection limit, and low investment and running costs. The paper compares the ability of alternative methods to meet these criteria. Variations were found, depending on the techniques used and the target organism of the analysis. Economic reasons can determine whether alternative methods can be used routinely. Adoption of these screening systems also can be hampered by lack of internationally coordinated and accepted validation protocols.
64 citations
TL;DR: LC was well suited for analyzing folate compositions of meat, fish, and other foods of animal origin and between-species differences in folate monoglutamate distributions were observed.
Abstract: A liquid chromatographic (LC) method with fluorescence and UV detection was used to determine the folate contents of fish, meat, fish and meat products, chicken, eggs, and milk consumed in Finland. 5-Methyltetrahydrofolate, tetrahydrofolate, 5-formyltetrahydrofolate, 10-formylfolic acid, and folic acid from 24 commodities obtained from supermarkets, retail stores, and different outlets in the Helsinki area were analyzed. Pooled samples were extracted at pH 6.0 in the presence of antioxidants and deconjugated with hog kidney deconjugase. Very low levels of folates were detected in meat and meat products. Fresh fish, fish sticks, and chicken meat contained reasonable amounts (3-13 micrograms/100 g) of tetrahydrofolate and 5-methyltetrahydrofolate. Egg yolk contained high concentrations of 5-methyltetrahydrofolate (140-150 micrograms/100 g); 10-formylfolic acid was also detected (14-17 micrograms/100 g). Between-species differences in folate monoglutamate distributions were observed. The highest levels of tetrahydrofolate, > 5 micrograms/100 g, were found in chicken meat and fillets of rainbow trout, whitefish, and baltic herring. Tetrahydrofolate was most abundant in fresh fish. LC was well suited for analyzing folate compositions of meat, fish, and other foods of animal origin. Recovery of added folates ranged from 49 to 96%.
62 citations
TL;DR: A statistical test was made of the Horwitz function, an empirical relationship between the reproducibility precision of an analytical method and the concentration of the analyte regardless of the nature of the matrix, analyte, and the method.
Abstract: A statistical test was made of the Horwitz function, an empirical relationship between the reproducibility precision of an analytical method and the concentration of the analyte regardless of the nature of the analyte, matrix, and the method. The large data set (7502 observations) was compiled by Horwitz from collaborative trials (method performance studies) spanning the period 1915 to 1995. The data followed the Horwitz function well down to concentrations of about 10 -8 (10 ppb), but they followed a more stringent specification at lower concentrations. This discrepancy may be due to special circumstances prevailing in collaborative trials at very low concentrations. Deviations of individual observations from the function were in large part accounted for by random variations. No consequential Improvement in precision with time was found.
TL;DR: In this article, a collaborative study was conducted involving 8 laboratories (including the authors' laboratories) to validate the streamlined enzymatic method for determination of beta-D-glucan in barley and oats.
Abstract: A collaborative study was conducted involving 8 laboratories (including the authors' laboratories) to validate the streamlined enzymatic method for determination of beta-D-glucan in barley and oats. In the method, the flour sample is cooked to hydrate and gelatinize beta-glucan, which is subsequently hydrolyzed to soluble fragments with the lichenase enzyme. After volume and pH adjustments and filtration, the solution is treated with beta-glucosidase, which hydrolyzes beta-gluco-oligosaccharides to D-glucose. D-Glucose is measured with glucose oxidase-peroxidase reagent. Other portions of lichenase hydrolysate are treated directly with glucose oxidase-peroxidase reagent to measure free glucose in test sample. If levels of free glucose are high, the sample is extracted first with 80% ethanol. For all samples analyzed, the repeatability relative standard deviation (RSD(r)) values ranged from 3.1 to 12.3% and the reproducibility relative standard deviation (RSD(R)) values ranged from 6.6 to 12.3%. The streamlined enzymatic method for determination of beta-D-glucan in barley and oats has been adopted first action by AOAC INTERNATIONAL
TL;DR: A multiresidue method to analyze liquid whole milk for 59 compounds was developed, and linear instrument response was observed for all detectors except the FPD which required a second-order calibration curve.
Abstract: A multiresidue method to analyze liquid whole milk for 59 compounds was developed. The method involves a single extraction and cleanup strategy for many classes of compounds--organophosphorus compounds (OPs), organochlorine compounds (OCs), N-methylcarbamates (MCs), etc. Initial extraction is performed with ethanol-ethyl acetate as solvent and sodium sulfate as drying agent. A portion of the extract is concentrated to an oily consistency, and target analytes are partitioned into acetonitrile. Further cleanup is achieved by sequential solid-phase extractions--octadecyl (C18)-bonded silica cartridges followed by aminopropyl (NH2)-bonded silica cartridges. The solvent is exchanged to acetone for analysis by gas chromatography (GC) with electrolytic conductivity, flame photometric (FPD) or mass spectrometric (MS) detection and to methanol for analysis by liquid chromatography with postcolumn derivatization. Typical limits of detection (LODs; peak-to-peak signal-to-noise ratio > or = 3) were 0.3 ppb for OPs, 0.9 ppb for OCs and MCs, and 9 ppb for mass-selective detection. From the level of quantitation (LOQ = 3.33 x LOD) to 10 x LOQ, linear instrument response was observed for all detectors except the FPD which required a second-order calibration curve. Average recoveries for spikes at the LOQ ranged from 69 to 127% with standard deviations of about 10%. Similar accuracy and precision were observed for fortifications at 5 x LOQ and 10 x LOQ. The method was used to analyze 20 milk samples from various liquid milk processing plants. Incurred residues were confirmed by high-resolution GC/MS and GC/MS/MS.
TL;DR: Application of a series of t-tests, conducted according to Sidak's modified Bonerroni t-procedure, showed that both techniques yielded accurate results for cereal reference materials, although some differences from certified and reference values were found for each element.
Abstract: A method is described for the determination of Pb, Cd, Cu, and Se in cereal samples. An atomic absorption spectrometer equipped with a transverse-heated graphite furnace with Zeeman background correction was used for all determinations. Sample preparation was performed by closed-vessel microwave digestion using nitric acid and focused openvessel microwave digestion using nitric acid-hydrogen peroxide. Both techniques were evaluated by using 15 cereal reference materials and comparing results with certified or reference values for each element. Cereal reference standards obtained from the Community Bureau of Reference (Europe), the National Institute of Standards and Technology (USA), the National Institute for Environmental Studies (Japan), the National Research Centre for Certified Reference Materials (People's Republic of China), and the Canadian Grain Commission were used. Application of a series of t-tests, conducted according to Sidak's modified Bonerroni t-procedure, showed that both techniques yielded accurate results for cereal reference materials. Some differences from certified and reference values, however, were found for each element.
TL;DR: Feedstuffs and mixed feeds used for poultry and pig nutrition in Colombia were analyzed for aflatoxins by using a liquid chromatographic technique with a limit of detection of 1 microgram/kg for each aflatoxin.
Abstract: Feedstuffs and mixed feeds used for poultry and pig nutrition in Colombia were analyzed for aflatoxins by using a liquid chromatographic technique with a limit of detection of 1 μg/kg for each aflatoxin (B 1 , B 2 , G 1 , and G 2 ). Samples of grain sorghum, maize, processed soybean, rice meal, cottonseed meal, and poultry and pig feeds, representative of Colombian production for the 1995-1996 harvest, were taken from feed-manufacturing plants in various cities. Aflatoxins were detected in 11 of 45 samples of sorghum, 4 of 33 samples of maize, 8 of 22 samples of rice meal, 15 of 17 samples of cottonseed meal, 1 of 12 samples of other feedstuffs, 12 of 30 samples of poultry feed, and 7 of 16 samples of pig feed. Aflatoxins were not detected in soybean. Only 9 of 58 positive samples contained total aflatoxin levels exceeding maximum tolerable limits in Colombia.
TL;DR: A validated method using the acetate derivatives of sterols instead of their silyl ethers is presented, and GC/mass spectrometric structure of the assigned retention times was confirmed for the sterols and triterpene diols.
Abstract: Alkaline hydrolysis was performed on a series of different vegetable oils. The unsaponifiable lipid matter was extracted with ethyl ether, and the class of 4,4-desmethylsterols (sterols) plus the triterpene diols (diols) erythrodiol, uvaol, and betulinol were isolated by thin-layer chromatography. A validated method using the acetate derivatives of sterols instead of their silyl ethers is presented. The acetate derivatives were analyzed by high resolution gas chromatography (HRGC). Retention time, precision, recovery studies, and absolute response factors were calculated for these esters, and GC/mass spectrometric structure of the assigned retention times was confirmed for the sterols and triterpene diols.
TL;DR: The acid hydrolysis-capillary GC method for determining total, saturated, unsaturated, and monosaturated fats in cereal products has been adopted by AOAC INTERNATIONAL.
Abstract: Fifteen laboratories participated in a collaborative study to determine total, saturated, unsaturated, and monounsaturated fats in cereal products by gas chromatographic (GC) analysis of fatty acid methyl esters (FAMEs). Cereal products, representing a wide range of cereal grains and processes, were hydrolyxed in 8N HCl and extracted with ethyl and petroleum ethers. FAMEs were produced by the reaction of the mixed ether extracts with sodium hydroxide in methanol (NaOH/MeOH) and then with boron trifluoride reagent (14% BF3 in MeOH). They were quantitatively determined by capillary GC. Total fat was calculated as the sum of individual fatty acids expressed as triglyceride equivalents in accordance with nutrition labeling guidelines. Saturated, unsaturated, and monounsaturated fats were calculated as sums of individual fatty acids. The total fat contents of samples ranged from 0.56 to 12.64%. A split design was used to determine performance parameters of results obtained by 15 laboratories on 24 samples. Of the 24 samples, 7 were blind duplicates and 5 were independent materials. Statistical analysis for total fat yielded a relative standard deviation for repeatability (RSDr) range of 1.32 to 13.30% and a relative standard deviation for reproducibility (RSDR) range of 4.42 to 22.82%. The goal of this study was to determine total fat, saturated fat, unsaturated, and monounsaturated fat in cereal-based products by complete extraction, methylation, and quantitation of total fatty acids. The acid hydrolysis-capillary GC method for determining total, saturated, unsaturated, and monosaturated fats in cereal products has been adopted by AOAC INTERNATIONAL.
TL;DR: In this paper, a rapid Fourier transform near-infrared (FT-NIR) spectroscopic method was developed for quantitative determination of the peroxide values (PVs) of edible oils.
Abstract: A rapid Fourier transform near-infrared (FT-NIR) spectroscopic method was developed for quantitative determination of the peroxide values (PVs) of edible oils. The method is based on the stoichiometric reaction of triphenylphosphine (TPP) with hydroperoxides to produce triphenylphosphine oxide (TPPO). Calibration standards were prepared by adding randomized amounts of TPPO and TPP to peroxide-free high-erucic-acid rapeseed (HEAR) to produce a calibration matrix spanning the concentrations of TPPO and residual TPP in oils having PVs in the range 0-100 after complete reaction of the hydroperoxides with added TPP. A partial-least-squares (PLS) calibration model for predicting PV was developed by using the NIR spectral region from 4710 to 4540 cm -1 , where TPP and TPPO both absorb. The resulting PLS calibration was linear, the cross-validation having a standard deviation (SD) of 1.36 PV over the analytical range. The method was validated by comparing the PLS-predicted PVs of oils spiked with tert-butyl hydroperoxide (TBHP) and those of naturally oxidized HEAR oils with the results obtained by using the American Oil Chemists' Society (AOCS) iodometric procedure. The FT-NIR PV method correlated very well (SD = 1.20) with the reference AOCS method for TBHP-spiked oil samples. Similar results were obtained for naturally oxidized HEAR oil, with a standard deviation of the difference for reproducibility of ± 1.11 PV for both methods. The analysis consists of adding about 0.04 mL TPP stock solution to 1 g oil, shaking, recording the spectrum, and using the PLS calibration to predict PV. Because of its simple and rapid stoichiometric reaction and its excellent correspondence to the iodometric method, the FT-NIR method provides a simple and alternative means of measuring PV. The FT-NIR method avoids the solvent and reagent disposal problems associated with the AOCS method and can be readily automated by appropriate programming of the FTIR spectrometer. Thus, it provides a simple and rapid analytical technique for determining PVs of fats and oils.
TL;DR: Fat from meat, dairy, and egg products was extracted by using Microwave-Assisted Process (MAP) technology under atmospheric pressure conditions with low solvent consumption, low energy consumption, reproducibility, and recoveries similar to or better than those of conventional extraction methods.
Abstract: Fat from meat, dairy, and egg products was extracted by using Microwave-Assisted Process (MAP) technology under atmospheric pressure conditions. Fat content was determined gravimetrically after extraction with microwaves and organic solvents that are transparent to microwaves relative to the sample. (In situ hydrolysis was performed for dairy and egg products.) Fat from the food sample migrated completely to the extractant when samples were irradiated with focused microwave for a total of 3 min for meat products, 1 min for dairy products, and 4 min for egg products. Unlike current methods used for determining fat in meat products, the microwave-assisted method does not require a dry sample, because moisture in the sample (around 75%) enhances the efficiency of extraction. No preprocessing was required for meat samples other than homogenization, which is critical, as it is for other current methods. In addition to speed and ease of use, the features of this technology are low solvent consumption, low energy consumption, reproducibility, and recoveries similar to or even better than those of conventional extraction methods.
TL;DR: DDE and HCH isomer levels were substantially higher than those found in a 1984-1987 survey, probably because the source of cow's milk has shifted from local dairy industries to mainland China over the past decade.
Abstract: A survey was conducted from 1993 through 1995 to monitor organochlorine pesticides and their metabolite residues in milk available in local Hong Kong markets. Of 252 samples analyzed, including pasteurized milk, fresh milk, and raw milk, 42 contained organochloride pesticide residues at levels exceeding the Extraneous Maximum Residue Limits of the Codex Committee on Pesticide Residues. DDE and HCH isomer levels were substantially higher than those found in a 1984-1987 survey, probably because the source of cow's milk has shifted from local dairy industries to mainland China over the past decade. Although organochlorine pesticides such as DDT and HCH have been banned in China since 1983, residues of such compounds may still persist in the environment and cause contamination through the food chain.
TL;DR: A collaborative study was conducted to test a modification to the AOAC fluorometric method for histamine that substitutes 75% methanol as the extracting solvent and concludes that the method for determination of putrescine and cadaverine in seafood has been adopted first action by AOac INTERNATIONAL.
Abstract: A collaborative study was conducted to test a modification to the AOAC fluorometric method for histamine (AOAC Official Method 977.13) that substitutes 75% methanol as the extracting solvent. All other steps remain unchanged. The extracts prepared with 75% methanol were also used to collaboratively test a gas chromatographic (GC) method for determination of putrescine and cadaverine in seafood. In the GC method, the extracted diamines are converted to fluorinated derivatives, the reaction mixtures are passed through solid-phase extraction columns, and the derivatives are quantitated by electron capture GC after separation on an OV-225 column. Fourteen laboratories using the GC method for putrescine and cadaverine and 16 laboratories using the fluorometric method for histamine analyzed 14 canned tuna and raw mahimahi (including blind duplicates and a spike) containing 0.2-2.6 ppm putrescine, 0.6-9.1 ppm cadaverine, and 0.6-154 ppm histamine. At the 5 ppm level, recoveries ranged from 71 to 102% for putrescine and 77 to 112% for cadaverine; the respective repeatability relative standard deviations (RSDr) were 5.2 and 15%, and the respective reproducibility relative standard deviations (RSDR) were 8.8 and 18%. At the 50 ppm level, histamine recoveries ranged from 84 to 125%, RSDr was 3.6%, and RSDR was 9.4%. The GC method for determination of putrescine in canned tuna and cadaverine in canned tuna and mahimahi has been adopted first action by AOAC INTERNATIONAL, and the AOAC Official Method 977.13, Histamine in Seafood, Fluorometric Method, has been modified.
TL;DR: Feed and polenta that contain fumonisins could be of concern because they are consumed in large amounts and are often the main nutrient source in Uruguay.
Abstract: A survey was conducted to evaluate fumonisins FB 1 and FB 2 in Uruguayan corn products. Sixty-four samples of different local brands were purchased from retail stores during a 15-month period and analyzed for FB 1 and FB 2 by methanol-water extraction, cleanup with a 1 mL strong-anion-exchange solid-phase extraction column, and liquid chromatography with o-pthaldialdehyde-2-mercaptoethanol derivatization and fluorescence detection. Contamination levels for FB 1 varied from 50 ng/g (detection limit) to 6342 ng/g. Values were highest in feed samples (up to 6342 ng/g), unprocessed corn kernel (up to 3688 ng/g), and milled products, which included polenta (up to 427 ng/g). They were lowest in processed corn kernel (up to 155 ng/g) and snacks (up to 314 ng/g). FB 2 was determined in one-fourth of the total samples and detected at trace levels in only one feed sample. The data demonstrated the natural occurrence of fumonisins in corn products in Uruguay. Feed and polenta that contain fumonisins could be of concern because they are consumed in large amounts and are often the main nutrient source in Uruguay.
TL;DR: In this article, sound and infested wheat kernels containing late-instar granary weevil larvae, as identified by X-ray analysis, were used to evaluate the ability of near-infrared spectroscopy to predict the presence of insect larvae in individual wheat kernels.
Abstract: Sound and infested wheat kernels containing late-instar granary weevil larvae, as identified by X-ray analysis, were used to evaluate the ability of near-infrared (NIR) spectroscopy to predict the presence of insect larvae in individual wheat kernels. Diffuse reflectance spectra at 1100-2500 nm were recorded from individual infested and sound kernels. Principal component analysis (PCA) of NIR spectra from sound kernels was used to construct calibration models by calculation of Mahalanobis distances. Calibration models were then applied to spectra obtained from both sound and infested kernels in a separate validation set. A 5-factor PCA model using data from a first-derivative spectral transformation was the best model for correctly classifying kernels in an expanded validation sample set, including 100% of sound, 93% of infested, 95% of sound air dried, 86% of infested air dried kernels, and 90% of sound kernels from 6 wheat varieties. Calibrations using the spectral region from 1100 to 1900 nm were least sensitive to kernel moisture differences. Similar results were obtained when discriminant analysis was applied to log 1/R data from selected discrete wavelengths of NIR spectra.
TL;DR: A liquid chromatographic (LC) method with fluorescence detection is presented for the analysis of 4 fluoroquinolones; enrofloxacin (ENRO), ciprofloxicin (CIPRO), sarafloxacIn (SARA), and difloxACin (DIFLX) in milk.
Abstract: A liquid chromatographic (LC) method with fluorescence detection is presented for the analysis of 4 fluoroquinolones; enrofloxacin (ENRO), ciprofloxacin (CIPRO), sarafloxacin (SARA), and difloxacin (DIFLX) in milk. The procedure consists of extraction of milk with acidified ethanol, isolation and retention on a cation exchange solid-phase extraction column, elution with basic methanol, and LC analysis with fluorescence detection. LC analysis is performed by isocratic elution using an acetonitrile-2% acetic acid (15 + 85) mobile phase and an Inertsil phenyl column with fluorescence detection at excitation and emission wavelengths of 278 and 450 nm, respectively. A target level of 10 ppb for each of the 4 fluoroquinolones has been established for this method. Average recovery from fortified raw milk samples (5-100 ppb each) based on a 5-point standard curve calculation was 70-90%, with relative standard deviations of < 15%.
TL;DR: A statistical methodology to verify the trueness of an analytical method in the presence of corrigible systematic errors is presented and was applied to spectrofluorometric determination of oxalates in spinach leaves.
Abstract: A statistical methodology to verify the trueness of an analytical method in the presence of corrigible systematic errors is presented. This protocol enables detection of constant and proportional components of error. By using the data set obtained in the Youden calibration with different sample test portions, the constant component of the error (Youden blank) can be determined. An analysis of covariance was applied to 3 calibration curves established with standard solutions and with standard additions to 2 different sample test portions. The slopes were compared, and the presence of any matrix-analyte interaction was detected. A method for removing the numerical components of systematic errors is proposed: a calculation procedure to obtain a correct analytical result and a statistical test to verify the correctness of analyte contents obtained from different calibrations. For demonstration purposes, the protocol was applied to spectrofluorometric determination of oxalates in spinach leaves.
TL;DR: The polymerase chain reaction (PCR), using primers for amplification of a 118-base pair DNA fragment from the virulence-associated spa region, present in all Shigella spp.
Abstract: The normal bacterial microflora of 4 commercially prepared salads (coleslaw, crab salad, carrot salad, and potato salad) and 3 vegetables (green pepper, onion, and cabbage) were evaluated Twenty-eight species of bacteria, including potential pathogens, were isolated The foods were artificially inoculated with an avirulent mutant strain of Shigella flexneri 5 (pHS1059) to develop a method for the rapid detection of Shigella spp Bacteria were separated from insoluble and particulate salad ingredients by filtration through shark skin filter paper and by low speed centrifugation S flexneri survived at 4 degrees C in all salads for at least 11 days and up to 20 days in crab salad The polymerase chain reaction (PCR), using primers for amplification of a 118-base pair DNA fragment from the virulence-associated spa region, present in all Shigella spp, was used to detect S flexneri in filtrates from salads inoculated with S flexneri 5 (pHS1059) DNA was amplified from all of the artificially contaminated salads and vegetables except green pepper After 3-5 days of storage, the PCR also amplified S flexneri DNA from salads that had been enriched with nutrients to increase the number of bacteria Green peppers contained a PCR inhibitory substance that was attenuated by dilution and enrichment before the PCR No amplification of DNA was observed in foods to which S flexneri had not been added
TL;DR: In this paper, 12 laboratories participated in a collaborative study to evaluate precision parameters of a liquid chromatographic method for analysis of the glycoalkaloids alpha-solanine and alpha-chaconine in potato tubers.
Abstract: Twelve laboratories participated in a collaborative study to evaluate precision parameters of a liquid chromatographic method for analysis of the glycoalkaloids alpha-solanine and alpha-chaconine in potato tubers. Samples consisted of frozen potato tuber homogenates distributed as 3 blind duplicates and 3 split-level pairs. The analytical method included aqueous extraction, workup on disposable solid-phase extraction cartridges, and reversed-phase chromatography with photometric detection at 202 nm. Results for alpha-solanine and alpha-chaconine were received from 10 and 9 laboratories, respectively. Relative standard deviations for reproducibility for alpha-solanine and alpha-chaconine were similar, ranging from 8 to 13% in the applied concentration range of 12 to 260 mg/kg fresh weight.
TL;DR: A capillary electrophoresis method and an electrospray ionization (ESI) liquid chromatography/mass spectrometry (LC/MS) confirmatory method were developed to analyze 12 sulfonylurea herbicides and one sulfonamide in runoff water and obtained good recoveries and adequate sensitivity at the 0.2 ppb level.
Abstract: A capillary electrophoresis (CE) method and an electrospray ionization (ESI) liquid chromatography/mass spectrometry (LC/MS) confirmatory method were developed to analyze 12 sulfonylurea herbicides and one sulfonamide (Flumetsulam) in runoff water. The water used for fortification was collected from a local marsh that contained high levels of potentially interfering compounds. Good recoveries and adequate sensitivity at the 0.2 ppb level (limit of quantitation) were obtained. A portion of the water was acidified and extracted with reversed-phase solid-phase extraction (SPE). Extracts were cleaned up with a tandem system consisting of a strong-anion exchange SPE cartridge stacked on an alumina SPE cartridge. CE/ultraviolet quantitation was achieved by capillary zone electrophoresis at pH 4.75 with 50 mM ammonium acetate buffer and an acetonitrile modifier. ESI LC/MS quantitation was achieved by using a time-scheduled selective-ion monitoring (positive mode) of the M + H ions for each compound. The extraction/cleanup procedure provided extracts such that in-source collision-induced dissociation gave product ions for confirmation at the 0.2 ppb fortification level.
TL;DR: The proactive approach to ensuring food safety termed hazard analysis critical control point (HACCP) was introduced in the 1960s by the Pillsbury Company, in collaboration with the U.S. Army Natick Laboratories and National Aeronautics and Space Administration, and is seen as forming the basis for harmonization of food inspection regulations necessitated by trade agreements.
Abstract: The proactive approach to ensuring food safety termed hazard analysis critical control point (HACCP) was introduced in the 1960s by the Pillsbury Company, in collaboration with the U.S. Army Natick Laboratories and National Aeronautics and Space Administration, to help guarantee that astronauts would not be incapacitated by the trauma of foodborne illness during space flights. The approach has subsequently been adopted as the standard food safety management system world-wide and is seen as forming the basis for harmonization of food inspection regulations necessitated by trade agreements such as General Agreement on Tariffs and Trade and North American Free Trade Agreement as the move toward globalization of trade in food products gains momentum. The new U.S. Department of Agriculture Mega-Reg requires mandatory introduction of HACCP, and the Food Safety Enhancement Program of Agriculture and Agri-food Canada, as well as the "due diligence" legislation of the European Union, is centered on HACCP principles.
TL;DR: Standard Reference Material 1846 (Infant Formula), which can be used as a control material for assigning values to in-house control materials and for validating analytical methods for measurement of proximates, vitamins, and minerals in infant formula and similar matrixes, was released in 1996.
Abstract: In 1996, the National Institute of Standards and Technology (NIST) released Standard Reference Material 1846 (Infant Formula), which can be used as a control material for assigning values to in-house control materials and for validating analytical methods for measurement of proximates, vitamins, and minerals in infant formula and similar matrixes. The SRM was manufactured by preparing a spray-dried formula base containing fat, protein, carbohydrates, and minerals and then combining that formula base with a dry-blend vitamin premix that supplied the vitamins. The Certificate of Analysis for SRM 1846 provides assigned values for concentrations of proximates (fat, protein, etc.), vitamins, and minerals for which product labeling is required by the Infant Formula Act of 1980 and by the Nutrition Labeling and Education Act of 1990. These assigned values were based on agreement of measurements by NIST and/or collaborating laboratories. Certified values are provided for vitamins A (trans), E, C, B2, and B6 and niacin. Noncertified values are provided for solids, ash, fat, nitrogen, protein, carbohydrate, calories, vitamin D, delta-tocopherol, gamma-tocopherol, vitamin B1, vitamin B12, folic acid, pantothenic acid, biotin, choline, inositol, calcium, phosphorus, magnesium, iron, zinc, copper, sodium, potassium, and chloride. Information values are provided for iodine, manganese, selenium, and vitamin K.