Levels Of Cross-contamination Research Articles

Carryover of Maduramicin from Feed Containing Cross-Contamination Levels into Eggs of Laying Hens

Maduramicin is a coccidiostat authorized as feed additive in the European Union for chickens and turkeys for fattening but not for laying hens, considering the risk of residues in eggs. The unavoidable cross-contamination of non-target feed with coccidiostats is regulated by Commission Directive 2009/8/EC and resulting carry-over in food by Commission Regulation (EC) No. 124/2009. To verify the compliance of the maximum levels for maduramicin in feed (50 μg/kg) and eggs (2 μg/kg), the carry-over from feed into eggs was investigated. Diets containing 10, 30, and 50 μg of maduramicin/kg of feed were fed to laying hens. Feed, egg white, and yolk were analyzed by LC-MS/MS. Maduramicin residues were only detected in in egg yolk. Feeding the 10 μg/kg maduramicin diet resulted in maduramicin concentrations up to 2.5 μg/kg in whole eggs, already exceeding the maximum level. A carry-over rate of 8% maduramicin from feed into eggs was calculated.

Transfer of flubendazole and tylosin at cross contamination levels in the feed to egg matrices and distribution between egg yolk and egg white

Chemical residues may be present in eggs from laying hens' exposure to drugs or contaminants. These residues may pose risks to human health. In this study, laying hens received experimental feed containing flubendazole or tylosin at cross contamination levels of 2.5, 5, and 10% of the therapeutic dose. Eggs were collected daily and analysis of the whole egg, egg white, and egg yolk was performed using liquid chromatography tandem mass spectrometry. Highest concentrations of the parent molecule flubendazole, as well as the hydrolyzed and the reduced metabolite, were detected in egg yolk. Residue concentrations of the parent molecule were higher compared with those of the metabolites in all egg matrices. No tylosin residue concentrations were detected above the limit of quantification for all concentration groups and in all egg matrices. Neither molecule exceeded the set maximum residue limits.

Experimental study: uptake of coccidiostats in vegetables

Experimental study: uptake of coccidiostats in vegetables

Residues of sulfadiazine and doxycycline in egg matrices due to cross-contamination in the feed of laying hens and the possible correlation with physicochemical, pharmacokinetic and physiological parameters

In the poultry industry, the widespread use of veterinary drugs such as antimicrobial compounds may lead to the presence of residues in whole eggs, egg white and egg yolk. During this study, laying hens received experimental feed containing sulfadiazine or doxycycline at cross-contamination levels of 2.5%, 5% and 10% of the therapeutic concentration. Since the therapeutic dose is 250 mg kg−1 for both substances, cross-contamination concentrations in the feed of 6.25, 12.5 and 25 mg kg−1 were expected. Whole egg, egg white and egg yolk samples were collected during the treatment and depletion period and were analysed via liquid chromatography-tandem mass spectrometry. For both drugs, a plateau phase was reached within 3–5 days and residue concentrations were detected in all egg matrices. For the 10% cross-contamination group, residual sulfadiazine concentrations of 208, 299 and 60 µg kg−1 and residual doxycycline concentrations of 455, 332, 206 µg kg−1 were detected in whole egg, egg white and egg yolk on day 13 of the treatment period, respectively. Both sulfadiazine and doxycycline had higher concentrations in egg white than in egg yolk, but the egg white–egg yolk ratio was higher for sulfadiazine than for doxycycline. As neither drug is allowed in Belgium for use in laying hens, residues may pose food safety concerns.

Comparison of Sanitizing Methods for Reduction of Attached Microorganisms on Various Kitchen Cutting Boards

Escherichia coli O157:H7 infection has been implicated in a number of outbreaks of illness linked to the consumption of foods. Handling raw meat contaminated with E. coli O157:H7 in the kitchen could easily contaminate the surface of cutting boards. Thus, levels of cross-contamination of E. coli O157:H7 from ground beef to cutting boards made of different materials and effects of cleaning methods on reducing E. coli O157:H7 were evaluated. Four types of cutting boards (wood, polyethylene, polypropylene, and acrylic) were selected and contaminated with ground beef inoculated with E. coli O157:H7. Levels of cross-contaminated E. coli O157:H7 on boards were then evaluated. For evaluation of cleaning methods, wiping with dry paper towel, wet paper towel, alcohol paper towel, chlorine paper towel were used to clean the contaminated cutting boards. Initial population of pathogens was 6.09 log CFU/g in ground beef. After 1 h contamination of the inoculated ground beef on the cutting boards, no significant difference were observed in levels of cross-contaminated E. coli O157:H7 depending on the cleaning materials except for the normal polyethylene surface. Order of efficacy in removing E. coli O157: H7 was as follows: alcohol > chlorine > wet > dry paper towel. Cleaning with alcohol sanitizer appeared as the most effective cleaning method for reducing E. coli O157: H7 population on kitchen cutting boards. These results could be used to develop kitchen safety guidelines for preventing foodborne outbreaks.

Residues of sulfadiazine and doxycycline in broiler liver and muscle tissue due to cross-contamination of feed

Veterinary drugs, such as antimicrobial compounds, are widely used in poultry and may lead to the presence of residues in matrices of animal origin, such as muscle and liver tissue. In this study, broilers received an experimental feed containing sulfadiazine or doxycycline at cross-contamination levels of 2.5, 5 and 10% of the therapeutic dose in feed. Breast and thigh muscle and liver samples were collected during treatment and depletion period and analysed via liquid chromatography–tandem mass spectrometry (LC–MS/MS). Concentrations reached a plateau phase 3–5 days after the start of experimental feeding. A rapid depletion of residues was noted after withdrawal of the experimental feed. No significant differences in measured concentrations were observed between the various muscle types. Residue concentrations for some experimental groups; the 10% group of sulfadiazine and the 5 and 10% group of doxycycline, however, exceeded their corresponding maximum residue limits (MRLs).

Regulatory issues in Europe

The EU food labelling regulation tells the food producer that all ingredients in a pre-packaged product need to be in the list of ingredients. There are some exceptions from this general rule, but theses exceptions can not be used if the ingredient is a recognised allergenic food on the EU list. It is also important to note that the producer is obliged to use an easily recognisable name. As an example it is not sufficient to write casein on the list of ingredients, because consumers may not know that casein is a milk ingredient. The producer must write e.g. casein (milk). This regulation only covers pre-packaged food and not food sold loose or in restaurants. This type of food is one of the leading causes of severe allergic reactions in people. The European Council adopted in December 2010 an opinion stating that allergen information on non pre-packaged food should be ‘mandatory’. If this proposal is agreed upon by the EU parliament it will be a great advantage for food allergic persons but also a big challenge for small businesses preparing foods sold loose e.g. in bakeries or served in restaurants. Current EU legislation also has not addressed directly the issue of allergen cross contamination. Whilst there is some voluntary guidance which includes qualitative advice for industry on how to assess and manage risk from allergenic foods, there is currently no advice from regulatory bodies or compliance authorities on levels of allergen cross contamination above which advisory labelling (such as ‘May Contain Nuts’) should be used. This current absence of defined thresholds has consequences for risk managers, who have to decide what level of allergenic food in a given product constitutes a health risk and therefore requires action to manage and/or communicate the risk.

Simultaneous detection of cow and buffalo species in milk from China, India, and Pakistan using multiplex real-time PCR

Asian countries are major producers of cow and buffalo milk. For quality and authenticity purposes, a multiplex real-time PCR assay was developed to specifically and simultaneously detect DNA from these 2 bovine species. Targeting the cytochrome b gene of mitochondrial DNA, common PCR primers amplified a 105-bp fragment, and 2 fluorescent probes specific to either cow or buffalo were designed for their identification. Specificity was successfully tested on 6 other species, including sheep and goat, and sensitivity reached 1% of cow DNA in buffalo DNA and vice versa. As an evaluation, the method was tested using 119 freeze-dried Asian milk samples from regional industrial milk facilities. Although these samples did not cover the entire Asian zone, the multiplex assay indicated that approximately 20% of the samples (mainly from India) showed high levels of cross-contamination of cow milk by buffalo milk, and vice versa. Fast, sensitive, and straightforward, this method is fit-for-purpose for the authenticity control of Asian milk.

Determination of eleven coccidiostats in animal feed by liquid chromatography–tandem mass spectrometry at cross contamination levels

A confirmatory multi-residue method has been developed to allow for the detection, confirmation and quantification of eleven coccidiostats in animal feed by liquid chromatography–tandem mass spectrometry (LC–MS/MS). The method can be used to determine halofuginone, robenidine, nicarbazin, diclazuril, decoquinate, semduramicin, lasalocid, monensin, salinomycin, narasin, maduramicin at levels relating to unavoidable carry over as stated in Regulation 2009/8/EC. Feed samples are extracted with water and acetonitrile with the addition of anhydrous magnesium sulphate and sodium chloride. The extract then undergoes a freezing out step before being diluted and injected onto the LC–MS/MS system. The LC–MS/MS system is run in MRM mode with both positive and negative electrospray ionisation and can confirm all eleven analytes in a run time of 19 min. The sensitivity of the method allows quantification and confirmation for all coccidiostats at a 0.5% carry over level. The method was validated over three days in accordance with of European legislation; Commission Decision 2002/657/EC. Validation criteria of accuracy, precision, decision limit (CCα), and detection capability (CCβ) along with measurement uncertainty are calculated for all analytes. The method was then successfully used to analyse a number of feed samples that contained various coccidiostat substances.

Determination of ionophore coccidiostats in feeding stuffs by liquid chromatography–tandem mass spectrometry. Part II. Application to cross-contamination levels and non-targeted feed

A fit to purpose multi-analyte method for the official control of six coccidiostats (monensin sodium, salinomycin sodium, narasin, lasalocid sodium, semduramicin sodium and maduramicin ammonium alpha) at cross-contamination concentration levels in poultry, cattle, pig and calf compound feed by liquid chromatography tandem mass spectrometry (LC–MS/MS) has been developed and in-house validated. The corresponding maximum levels have been recently introduced by European legislation. The method developed involved a simple extraction of the coccidiostats from the feed samples followed by centrifugation and filtration of the supernatants for all matrices. For calf feed an additional de-fattening step of the filtrated supernatants with n-hexane was necessary. The resulting supernatants were submitted to chromatographic analysis. The analytes were quantified by a modified approach of the standard additions technique applied to the extracts, hence allowing a workload comparable to matrix-matched standard calibration curves. A further simplification of this technique was reached by applying the same addition levels of the target analytes for different concentration ranging from 0.5× maximum level up to 2.5× maximum level (universal approach). The concentration independent intermediate precision expressed in terms of relative standard deviation varied between 3 and 12% (except for maduramicin ammonium alpha and semduramicin sodium up to 21%) and the recovery rates ranged from 80 to 111%, depending on the target analyte and matrix. The limits of detection (LOD) and limits of quantification (LOQ) were different for the various analyte/matrix/instrument combinations but all LOQs were in the 0.01–0.65 mg kg −1 range, hence well below the target concentrations of each analyte. Based on the obtained method performance characteristics the method is considered fit for the intended purpose.

Unnecessary roughness? Testing the hypothesis that predators destined for molecular gut‐content analysis must be hand‐collected to avoid cross‐contamination

Molecular gut-content analysis enables detection of arthropod predation with minimal disruption of ecosystem processes. Mass-collection methods, such as sweep-netting, vacuum sampling and foliage beating, could lead to regurgitation or rupturing of predators along with uneaten prey, thereby contaminating specimens and compromising resultant gut-content data. Proponents of this 'cross-contamination hypothesis' advocate hand-collection as the best way to avoid cross-contamination. However, hand-collection is inefficient when large samples are needed, as with most ecological research. We tested the cross-contamination hypothesis by setting out onto potato plants immature Coleomegilla maculata and Podisus maculiventris that had been fed larvae of either Leptinotarsa decemlineata or Leptinotarsa juncta, or unfed individuals of these predator species along with L.decemlineata larvae. The animals were then immediately re-collected, either by knocking them vigorously off the plants onto a beat cloth and capturing them en masse with an aspirator ('rough' treatment) or by hand-searching and collection with a brush ('best practice'). Collected predators were transferred in the field to individual vials of chilled ethanol and subsequently assayed by PCR for fragments of cytochrome oxidase I of L.decemlineata and L.juncta. Ten to 39 per cent of re-collected fed predators tested positive by PCR for DNA of both Leptinotarsa species, and 14-38% of re-collected unfed predators contained L.decemlineata DNA. Overall levels of cross-contamination in the rough (31%) and best-practice (11%) samples were statistically different and supported the cross-contamination hypothesis. A pilot study on eliminating external DNA contamination with bleach prior to DNA extraction and amplification gave promising results.

Whole-leaf wash improves chlorine efficacy for microbial reduction and prevents pathogen cross-contamination during fresh-cut lettuce processing.

Currently, most fresh-cut processing facilities in the United States use chlorinated water or other sanitizer solutions for microbial reduction after lettuce is cut. Freshly cut lettuce releases significant amounts of organic matter that negatively impacts the effectiveness of chlorine or other sanitizers for microbial reduction. The objective of this study is to evaluate whether a sanitizer wash before cutting improves microbial reduction efficacy compared to a traditional postcutting sanitizer wash. Romaine lettuce leaves were quantitatively inoculated with E. coli O157:H7 strains and washed in chlorinated water before or after cutting, and E. coli O157:H7 cells that survived the washing process were enumerated to determine the effectiveness of microbial reduction for the 2 cutting and washing sequences. Whole-leaf washing in chlorinated water improved pathogen reduction by approximately 1 log unit over traditional cut-leaf sanitization. Similar improvement in the reduction of background microflora was also observed. Inoculated "Lollo Rossa" red lettuce leaves were mixed with noninoculated Green-Leaf lettuce leaves to evaluate pathogen cross-contamination during processing. High level (96.7% subsamples, average MPN 0.6 log CFU/g) of cross-contamination of noninoculated green leaves by inoculated red leaves was observed when mixed lettuce leaves were cut prior to washing in chlorinated water. In contrast, cross-contamination of noninoculated green leaves was significantly reduced (3.3% of subsamples, average MPN <or=-0.3 log CFU/g) when the mixed leaves were washed in chlorinated water before cutting. This result suggests that whole-leaf sanitizing washes could be a practical strategy for enhancing the efficacy of chlorine washes for pathogen reduction and cross-contamination prevention.

AT_CHLORO, a Comprehensive Chloroplast Proteome Database with Subplastidial Localization and Curated Information on Envelope Proteins

Recent advances in the proteomics field have allowed a series of high throughput experiments to be conducted on chloroplast samples, and the data are available in several public databases. However, the accurate localization of many chloroplast proteins often remains hypothetical. This is especially true for envelope proteins. We went a step further into the knowledge of the chloroplast proteome by focusing, in the same set of experiments, on the localization of proteins in the stroma, the thylakoids, and envelope membranes. LC-MS/MS-based analyses first allowed building the AT_CHLORO database (http://www.grenoble.prabi.fr/protehome/grenoble-plant-proteomics/), a comprehensive repertoire of the 1323 proteins, identified by 10,654 unique peptide sequences, present in highly purified chloroplasts and their subfractions prepared from Arabidopsis thaliana leaves. This database also provides extensive proteomics information (peptide sequences and molecular weight, chromatographic retention times, MS/MS spectra, and spectral count) for a unique chloroplast protein accurate mass and time tag database gathering identified peptides with their respective and precise analytical coordinates, molecular weight, and retention time. We assessed the partitioning of each protein in the three chloroplast compartments by using a semiquantitative proteomics approach (spectral count). These data together with an in-depth investigation of the literature were compiled to provide accurate subplastidial localization of previously known and newly identified proteins. A unique knowledge base containing extensive information on the proteins identified in envelope fractions was thus obtained, allowing new insights into this membrane system to be revealed. Altogether, the data we obtained provide unexpected information about plastidial or subplastidial localization of some proteins that were not suspected to be associated to this membrane system. The spectral counting-based strategy was further validated as the compartmentation of well known pathways (for instance, photosynthesis and amino acid, fatty acid, or glycerolipid biosynthesis) within chloroplasts could be dissected. It also allowed revisiting the compartmentation of the chloroplast metabolism and functions.

Silver ion antimicrobial technology: decontamination in a nursing home

This study aimed to quantify the reduction of bacterial contamination in a nursing home achieved by the presence of silver ion-treated antimicrobial products (BioCote®). BioCote® products were integrated into a single-occupancy residence and swabs were collected over a five-month period from silver-treated products in this residence and equivalent, untreated products in a control residence. Swabs were cultured for total viable counts of bacteria. A mean difference of 94.8% in bacterial counts was observed on BioCote®-treated surfaces compared to untreated products in the control environment. Bacterial counts from a number of untreated objects in the test residence were also lower than equivalent untreated objects in the control environment suggesting reduced levels of cross-contamination in the test environment. Counts of bacteria present in the test environment before antimicrobial treatment support the explanation that reduction of bacterial numbers in that environment over the study period was primarily due to the efficacy of antimicrobial products used. Further studies are needed to determine the beneficial clinical outcome that consistently cleaner environments might offer their patients.

PCR-based amplification and analysis of specific viral sequences from individual plant cells

Plant virus diversity and the spatial distribution of viral strains or isolates are studied at many different scales: global, regional, local, and even within a single host in different organs or tissues. However, one level that has been totally lacking at the extremity of this scale is that of the single cell. The technical difficulties involved in isolating individual cells from infected plants, and the lack of an efficient diagnostic procedure allowing the specific detection of viral sequences with no major contamination from other cells, have precluded such single cell analysis to date. This paper describes the preparation of protoplasts from plants infected with Cauliflower mosaic virus (CaMV), and their decontamination and separation using a technique requiring no specialised equipment. Efficient single-cell nested-PCR procedures (both standard and high-resolution-melting) were developed to allow efficient amplification and analysis of viral sequences from isolated single cells. Moreover, the specific identification of two CaMV variants in different cells demonstrated a very low level of cross-contamination. This technique paves the way for the future development of numerous applications of broad interest in the study of viral diversity and population genetics of plant viruses at the cellular level.

Decomplexing biofluids using microchip based acoustophoresis

Highly efficient washing and extraction of microbeads to decomplex analytes ranging from small peptides to large viruses was realised in a microscaled continuous flow format. The bead washing principle reported herein is based on acoustophoresis, i.e. the primary acoustic radiation force in an ultrasonic standing wave and laminar flow properties are utilised to translate bioanalytes trapped on functionalised microbeads from one carrier fluid to another. The carry-over of non-specific material ranges from 1 to 50 ppm relative to input levels depending on application, making acoustophoresis suitable for extraction of rare species from complex environments. Selective extraction of a phosphopeptide relative to its unphosphorylated counterpart is demonstrated using metal oxide affinity capture (MOAC) beads and MALDI-TOF MS readout. Acoustophoresis of microbeads activated with specific binders could be used to capture phage viral particles. The efficiency of the acoustophoretic washing principle was demonstrated by an unspecific phage cross contamination level of only 10(-6) of that in the input bead/phage mixture. The continuous flow format makes acoustophoretic washing flexible regarding sample volume and also allows for easy integration into a sequence of particle handling and analytical unit operations.

Impact of Wash Water Quality on Sensory and Microbial Quality, Including Escherichia coli Cross-Contamination, of Fresh-Cut Escarole

The influence of wash water quality on the microbial load and sensory quality of fresh-cut escarole was evaluated. Additionally, the degree of Escherichia coli cross-contamination between inoculated and uninoculated products after washing was also studied. Three types of wash water, i.e., potable water, diluted recirculated water, and recirculated water, containing different microbial counts and organic loads, were used. Results showed that microbial load (P > 0.02) and sensory quality (P > 0.625) of the product were not influenced by the water quality after washing and storage. Cross-contamination between inoculated and uninoculated products was observed after washing, as there was significant transmission of E. coli cells from the product to the wash water (P < 0.001). When fresh-cut escarole was contaminated at a high inoculum level (5.1 log CFU/g), wash water quality influenced the level of cross-contamination, as the highest E. coli load (P < 0.001) was shown in uninoculated fresh-cut escarole washed with recirculated water. However, when fresh-cut escarole was contaminated at a low inoculum level (3.2 log CFU/g), the wash water quality did not influence the level of cross-contamination, as E. coli slightly increased, although not at a statistically significant level, after the uninoculated product was washed with recirculated water (P > 0.035). Therefore, the contamination level may impact the effectiveness of water quality to reduce pathogen concentrations. It was clearly observed that cross-contamination of fresh-cut escarole with E. coli occurs, thereby suggesting that small amounts of contamination could impact the overall product and indicating the necessity of using wash water sanitizers to eliminate pathogens.

Heparan Sulfate Regulates Self-renewal and Pluripotency of Embryonic Stem Cells

Embryonic stem (ES) cell self-renewal and pluripotency are maintained by several signaling cascades and by expression of intrinsic factors, such as Oct3/4 and Nanog. The signaling cascades are activated by extrinsic factors, such as leukemia inhibitory factor, bone morphogenic protein, and Wnt. However, the mechanism that regulates extrinsic signaling in ES cells is unknown. Heparan sulfate (HS) chains are ubiquitously present as the cell surface proteoglycans and are known to play crucial roles in regulating several signaling pathways. Here we investigated whether HS chains on ES cells are involved in regulating signaling pathways that are important for the maintenance of ES cells. RNA interference-mediated knockdown of HS chain elongation inhibited mouse ES cell self-renewal and induced spontaneous differentiation of the cells into extraembryonic endoderm. Furthermore, autocrine/paracrine Wnt/beta-catenin signaling through HS chains was found to be required for the regulation of Nanog expression. We propose that HS chains are important for the extrinsic signaling required for mouse ES cell self-renewal and pluripotency.

A Simple and Reliable Method To Verify the Authenticity and Purity of Human Myeloma Cell Lines.

The availability of human myeloma cell lines (HMCLs) has drastically benefited out understanding of multiple myeloma (MM). They represent essential resources to the myeloma research community at large who use them to identify and more importantly validate oncogenic events in MM. Furthermore, they represent the front line tools in efforts to identify novel therapeutic agents for MM patients. However, the myeloma research community is not immune to problems of cell line contamination (mixed populations) or systemic errors where HMCLs are labeled incorrectly. As the community evolves towards the development of tailor medicine it is essential that our basic tools are both pure and correct. Otherwise, a potentially beneficial therapeutic agent designed for a specific patient subset maybe lost simply because of a simple laboratory mix-up at some point over the years. To that end we have developed a simple PCR based method that can be used to validate the purity and authenticity of HMCLs. First two reference collections of over 50 HMCL maintained at the NCI and Mayo Clinic Arizona were compared using microsatellite fingerprinting. This process identified several previously unnoticed discrepancies. First, in both labs several cell lines that reportedly originated from different patients had the same fingerprints. These include the following unexpected pairs; ANBL-6 and DP–6, CAG and ARP–1, KMS–11 and KMS–20, KMS–11 and KMS–21PE/BM, JIM3 and KPMM2. Second, both KP–6 and KAS6/1 showed a level of cross-contamination with ANBL–6. All of the discrepant cell lines were requested from the original contributor and those that were available were retested. After this step we had identified unique fingerprints for ANBL–6, DP–6, KMS–11, and KMS–20. Furthermore, pure populations of KP–6 and KAS6/1 were confirmed. However, CAG and ARP–1 still had an identical fingerprint. Since the use of microsatellite fingerprinting is an expensive task and the identification of cross-contamination is not very robust we set out to develop better method. We decided to use a simple qualitative PCR method, as the binomial presence or absence of a band makes the interpretation of the fingerprint extremely easy. Furthermore, the high sensitivity of a qualitative PCR can pick up a small amount of contamination in the culture that can be lost in microsatellite analysis. This method involves a multiplex PCR screen that simultaneously interrogates 10 regions of the human genome. The screen is divided into two reactions, one with a panel of highly polymorphic copy number variations (CNV) that are often completely absent in some individuals, and a second one based on known biologic events present in the cell lines. The integration of the results from the CNV and Biological Fingerprints will identify each HMCL as a unique entity. We validated the methodology by confirming that this qualitative screen could pick up the cross–contamination identified in the original KP–6 and KAS6/1 samples. As our understanding of myeloma increases and we strive to develop new therapies for specific biological entities it will be essential that groups confirm both the authenticity and purity of their test cultures. We hope that widespread use of this simple screening methodology will significantly improve the quality and reproducibility of assays carried out in labs around the world.

Multi-allergen screening immunoassay for the detection of protein markers of peanut and four tree nuts in chocolate

A multiresidue enzyme immunoassay was developed to check for the presence of markers of peanut, hazelnut, almond, cashew and Brazil nuts in a single run. The assay was designed under the competitive indirect format and adapted for screening purposes applied to chocolate samples. The limit of detection for this assay was below 1 µg g−1 protein for each allergenic food. In most cases, the high specificity of the antibodies used allowed the identification of each particular allergenic food with no possible confusion. This assay was proven to be useful as part of an analytical procedure involving the identification of the unknown allergenic food among peanut and other tree nuts in recalled samples before the application of a quantitative technique to determine the level of cross-contamination.