Food allergen detection by mass spectrometry: the role of systems biology

Abstract

Food allergy prevalence is rising worldwide, motivating the development of assays that can sensitively and reliably detect trace amounts of allergens in manufactured food. Mass spectrometry (MS) is a promising alternative to commonly employed antibody-based assays owing to its ability to quantify multiple proteins in complex matrices with high sensitivity. In this review, we discuss a targeted MS workflow for the quantitation of allergenic protein in food products that employs selected reaction monitoring (SRM). We highlight the aspects of SRM method development unique to allergen quantitation and identify opportunities for simplifying the process. One promising avenue identified through a comprehensive survey of published MS literature is the use of proteotypic peptides, which are peptides whose presence appears robust to variations in food matrix, sample preparation protocol, and MS instrumentation. We conclude that proteotypic peptides exist for a subset of allergenic milk, egg, and peanut proteins. For less studied allergens such as soy, wheat, fish, shellfish, and tree nuts, we offer guidance and tools for peptide selection and specificity verification as part of an interactive web database, the Allergen Peptide Browser (http://www.AllergenPeptideBrowser.org). With ongoing improvements in MS instrumentation, analysis software, and strategies for targeted quantitation, we expect an increasing role of MS as an analytical tool for ensuring regulatory compliance.

Figure 1

Workflow for allergen quantitation using MS.

Figure 2

Bos d 9 (α-S1-casein) rose plot and protein sequence highlighting peptides HQGLPQEVLNENLLR (blue, 10 publications), FFVAPFPEVFGK (red, 16 publications), and YLGYLEQLLR (green, 16 publications) as proteotypic.

Figure 3

Variation in proteotypic peptide status among allergens. (a–d) Allergenic proteins with proteotypic peptides (itemized in Table 1). (a) Milk protein Bos d 10. (b) Egg protein Gal d 4. (c) Peanut protein Ara h 2. (d) Peanut protein Ara h 3.0101. (e, f) Examples of allergenic proteins with insufficient data for proteotypic peptide determination. (e) Egg protein Gal d 3. (f) Soy protein Gly m 8.

Figure 4

Comparison of peptide publication count with ESP Predictor and CONSeQuence peptide detectability scores for five allergenic proteins with proteotypic peptides. For Ara h 2, the Ara h 2.0101 isoform has been used, whereas for Ara h 3, the Ara h 3.0101 isoform has been used.