Targeted mass spectrometry quantification of total soy protein residues from commercially processed ingredients for...

Soybean is one of the most commonly allergenic foods in the U.S. However, the variety of commercial soy ingredients used in the food industry makes soybean a challenging allergen to detect and quantify. The processing methods used to produce soy-derived ingredients result in protein modifications that often substantially impact detection and quantification with commonly used antibody-based methods. This study aimed to develop a mass spectrometry (MS)-based method capable of quantifying commercially processed soy ingredients in food matrices. A quantification strategy using external standards with internal calibrants was developed and evaluated, resulting in the ultimate use of a matrix-independent standard curve of non-roasted soy flour with milk proteins as carrier proteins. The method performance was evaluated by quantifying six soy-derived ingredients in incurred food matrices using three quantification strategies. Out of the twelve ingredient-matrix combinations with 10 ppm incurred total soy protein, eight had maximum recoveries between 60 and 120% using the full standard curve strategy. Other quantification strategies may be useful for internal quality control and interlaboratory calibrations. Compared with three commercial ELISA kits, the MS method showed a substantial advantage in quantifying the highly processed soy proteins in food matrices. SIGNIFICANCE: The ability to quantify undeclared soy protein in food products regardless of the soy ingredient source is essential for food allergen management, risk assessment, and regulatory enforcement. The MS-based method described here is able to reliably quantify six different soy-derived ingredients incurred in a model processed food. When compared with existing commercial ELISA methods, the MS method is much less affected by matrices and ingredient types, indicating its wider applicability to a range of soy-derived ingredients and processed products.