An MS-based method, combining reversed-phase capillary liquid chromatography (capillary LC) with quadrupole time-of-flight tandem mass spectrometry (nano-ESI Q-TOF MS/MS), was developed with the aim of identifying a set of peptides that can function as markers for peanut allergens. Emphasis was given to the identification of the three major peanut allergens Ara h 1, Ara h 2, and Ara h 3, because these proteins are considered to represent >30% of the total protein content of peanut and are directly relevant for the allergenic potential of this food. The analytical data obtained were used to perform databank searching in combination with de novo sequencing and led to the identification of a multitude of sequence tags for all three peanut allergens. Food processing such as roasting of peanuts is known to affect the stability of proteins and was shown to influence the detection of allergen sequence tags. The analysis of raw and roasted peanuts allowed the identification of five peanut-specific sequence tags that can function as markers of the specific allergenic proteins. For Ara h 1, two peptide markers were proposed, namely, VLEENAGGEQEER (m/z 786.88, charge 2+) and DLAFPGSGEQVEK (m/z 688.85, charge 2+), whereas for Ara h 2 only one peptide, RQQWELQGDR (m/z 439.23, charge 3+), was found to satisfy the required conditions. For Ara h 3, the two specific peptides, SPDIYNPQAGSLK (m/z 695.35, charge 2+) and SQSENFEYVAFK (m/z 724.84, charge 2+), were selected. Other peptides have been proposed as indicative for food processing.
The results of an inter-laboratory study with five commercially available peanut ELISA test kits to detect and quantify peanut residues in two food matrices (biscuit and dark chocolate) at four different concentrations (0-10 mg peanut kg(-1) matrix corresponding to about 0-2.5 mg peanut protein kg(-1) matrix) are reported. In general the five ELISA test kits evaluated could detect peanut protein in the two food matrices. In three cases, the study challenged the test kits beyond their intended use for quantification below the manufacturers' defined cut-off limits. Generally, all five ELISA test kits performed well in the concentration range 5-10 mg kg(-1) rather than in the low concentration range (2.0 or 2.5 mg kg(-1)). The variation in the found recoveries of peanut between the different test kits had a spread of 44-191% across all concentrations. The quantification characteristics between test kits differed significantly at the very low mg kg(-1) level. Two test kits performed well even at concentrations below 5 mg kg(-1) with reproducibilities of 27-36% for biscuits and 45-57% for chocolate.
The measurement of gluten in processed food products in support of regulatory limits is performed routinely. Mass spectrometry is emerging as a viable alternative to ELISA based methods. Here we outline a set of peptide markers that are representative of gluten and consider the end user's needs in protecting those with coeliac disease. The approach taken has been applied to wheat but can be easily extended to include other species potentially enabling the MS quantification of different gluten containing species from the identified markers.
The International Measurement Evaluation Programme (IMEP) is an interlaboratory comparison scheme, founded, owned and coordinated by the Institute for Reference Materials and Measurements (IRMM) since 1988. IMEP-9 is the third round of trace elements in water evaluation following IMEP-3 and IMEP-6. Reference values for 15 elements stating total concentrations and combined uncertainties (according to GUM) were established. The reference values were established mainly by isotope dilution mass spectrometry (IDMS) as a primary method of measurement, and values traceable to the SI were obtained. The four elements that could not be certified by IDMS were assigned values by means of other measurement techniques. Results from 201 laboratories from 35 countries and four continents were evaluated against the reference values and the comparability between the laboratories is presented graphically.
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