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Diaz-Amigo C.,Us Fda Center For Food Safety And Applied Nutrition
Food Analytical Methods | Year: 2010

There are several enzyme-linked immunosorbent assay (ELISA) kits in the market that have been proven to be useful for the determination of egg in foods. However, inconsistent results that are obtained when different kits are used make the selection of one kit over another very difficult. Two different approaches were used to help understand why results vary among kits. Different kits were used to analyze spiked egg material [NIST reference material (RM) 8445] in wheat flour (raw ingredients) and cookies containing egg as an ingredient baked for different periods of time (processed food). These results were compared with immunoblotting using conjugated antibodies from the commercial kits to determine the antibody specificity and sample extraction efficiency. ELISA results can be difficult to compare because reporting units differ among kits. Results from both ELISA and immunoblotting are in agreement regarding the decreased detection of proteins in baked cookie extracts. Moreover, immunoblotting showed that this reduction is due to reduced protein content in these extracts. However, a properly selected extraction solution may help improve the solubility of certain egg proteins in processed foods. Harmonization of the reporting unit system along with the use of a common reference material is recommended as the path forward in the standardization of detection methods for food allergens. This would assist the end user in making an informed decision regarding the selection of the most appropriate kit for his or her purpose. © 2009 Springer Science+Business Media, LLC.

Diaz-Amigo C.,Us Fda Center For Food Safety And Applied Nutrition
Food Analytical Methods | Year: 2010

Milk and milk derivatives are common ingredients in food products. Undeclared milk is one of the leading causes of recalls in many countries, including the USA, and cases of allergic reactions have been reported due to unexpected exposures. There are commercial enzyme-linked immunosorbent assay (ELISA) kits available to the food industry to comply with the law by ensuring label accuracy and to identify potential sources of cross-contact. These kits are also used by regulatory agencies as part of their compliance programs. However, none of the commercial ELISAs for milk have been validated. Performance of ELISA kits for food allergens is affected by matrix, food processing, and stability and solubility of target proteins, among others factors. The performance of different commercial kits for milk allergens was evaluated by comparing a standard [National Institute of Standards and Technology (NIST) SRM #1549] spiked in wheat flour. We also compared the effect of food processing on detectability of milk proteins from incurred peanut butter cookies baked at various times. Kits differed in their ability to detect heat-treated milk proteins in baked cookies. Immunoblots clearly showed differences in antibody specificities and in their ability to detect proteins in processed foods. Factors such as undefined antibody specificity and differences in sample extraction solutions, materials used for calibrators, and reporting units contribute to variability of results among test kits and, hence, to increased uncertainty regarding the most appropriate use of the kits. Moreover, the use of incurred vs. spiked samples may affect protein recovery and, therefore, jeopardize the quantitative nature of the kit. © 2009 Springer Science+Business Media, LLC.

Anderson M.,Rti International | Jaykus L.-A.,North Carolina State University | Beaulieu S.,Rti International | Dennis S.,Us Fda Center For Food Safety And Applied Nutrition
Food Control | Year: 2011

Foodborne disease outbreaks and cases associated with fresh produce have increased over the past decade. In developing approaches to prevent or reduce illnesses from consumption of contaminated produce, new tools are needed to identify and prioritize appropriate efforts. The purpose of this study was to develop a semi-quantitative risk ranking tool (Pathogen-Produce Pair Attribution Risk Ranking Tool, or P3ARRT) to rank the relative public health impact of pathogen-produce commodity combinations, based on explicit data-driven criteria. To identify candidate pathogen-commodity pairs, a database was created that included all published reports of fresh produce-associated outbreaks in the United States. A total risk score was calculated for each pathogen-commodity pair as the summation of nine criteria scores multiplied by the respective criteria weighting. A total of 53 pathogen-produce commodity pairs were included in the risk ranking, and based on scenario and sensitivity analyses, enterohemorrhagic E. coli in leafy greens consistently ranked first, followed by Salmonella spp. in tomatoes, and Salmonella spp. in leafy greens. The P3ARRT model provides a systematic, transparent, and customizable tool with which to prioritize produce pathogen-commodity pairs for further, more rigorous risk assessment modeling and evaluation efforts. The tool is available to the public at www.FoodRisk.org. © 2011 Elsevier Ltd.

Newsome G.A.,Nova Research Inc. | Ackerman L.K.,Us Fda Center For Food Safety And Applied Nutrition | Johnson K.J.,U.S. Navy
Journal of the American Society for Mass Spectrometry | Year: 2016

Post-plasma ambient desorption/ionization (ADI) sources are fundamentally dependent on surrounding water vapor to produce protonated analyte ions. There are two reports of humidity effects on ADI spectra. However, it is unclear whether humidity will affect all ADI sources and analytes, and by what mechanism humidity affects spectra. Flowing atmospheric pressure afterglow (FAPA) ionization and direct analysis in real time (DART) mass spectra of various surface-deposited and gas-phase analytes were acquired at ambient temperature and pressure across a range of observed humidity values. A controlled humidity enclosure around the ion source and mass spectrometer inlet was used to create programmed humidity and temperatures. The relative abundance and fragmentation of molecular adduct ions for several compounds consistently varied with changing ambient humidity and also were controlled with the humidity enclosure. For several compounds, increasing humidity decreased protonated molecule and other molecular adduct ion fragmentation in both FAPA and DART spectra. For others, humidity increased fragment ion ratios. The effects of humidity on molecular adduct ion fragmentation were caused by changes in the relative abundances of different reagent protonated water clusters and, thus, a change in the average difference in proton affinity between an analyte and the population of water clusters. Control of humidity in ambient post-plasma ion sources is needed to create spectral stability and reproducibility. [Figure not available: see fulltext.] © 2015 American Society for Mass Spectrometry.

Newsome G.A.,Nova Research Inc. | Ackerman L.K.,Us Fda Center For Food Safety And Applied Nutrition | Johnson K.J.,U.S. Navy
Analytical Chemistry | Year: 2014

Unstable explosive hexamethylene triperoxide diamine (HMTD) is dangerous in quantity and benefits from the minimal sampling handling associated with atmospheric pressure chemical ionization for mass spectral analysis. Seasonal variation observed in HMTD mass spectra suggested a humidity dependence. Therefore, direct analysis in real time (DART) ionization mass spectra were acquired at a range of humidity values. An enclosure was designed to fit around the ion source and mass spectrometer inlet at atmospheric pressure. The enclosure was supplied with controlled amounts of humidified air from a test atmosphere generator to create programmable conditions for ambient analysis. The relative abundance and fragmentation of analyte ions were observed to change reliably with changing humidity values and, to a lesser degree, temperature. Humidity at such plasma-based ion sources should be regulated to avoid ∼90% shifts in relative ion abundance and provide stability and reproducibility of HMTD analysis. (Figure Presented). © 2014 American Chemical Society.

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