Identification and characterization of allergens in spices by mass spectrometry

Background One of the major sources of hidden allergens in food is the use of spices that contain undeclared allergenic ingredients. Sesame and mustard are highly relevant in this context, as both seeds are frequently used in a variety of spices and can elicit severe allergenic reactions. Major allergens of mustard and sesame belong to the 2S-albumin family of seed storage proteins. 2S-albumins are members of the prolamin superfamily and are widely distributed in seeds and tree nuts. 2S-albumins are synthesized as a single precursor protein with about 13 kDa size that is subjected to extensive posttranslational proteolytic processing. The mature 2S albumins are composed of two subunits of approximately 9-10 kDa and 3-4 kDa size, respectively, which are linked by disulfide bridges. The 2S albumins are encoded by a multigene family possibly leading to numerous isoforms that may show considerable differences in their structures and allergenicity. The precise number, amount and characteristics of 2S albumin isoforms present in mustard and sesame however still remain unclear. One characteristic modification found is the C-terminal clipping of the small subunit that has been exemplarily described for Ses i 1 [1].