Allergy to yellow mustard (YM; Sinapis alba L.) seed proteins has been reported and is currently seen as a constraint that hampers expansion of YM protein utilization. The most predominant allergenic protein of YM seed has been recognized as Sin a 1. In this study, Sin a 1 was purified ( S. alba var. Andante), rabbit polyclonal antibodies (pAb) specific to Sin a 1 were generated, and a sandwich enzyme-linked immunosorbent assay (S-ELISA) was developed to detect and quantify Sin a 1 from YM. The S-ELISA method using Sin a 1-pAb and its horseradish peroxidase conjugate resulted in a detection limit of 0.3 microg/mL for purified Sin a 1. The Sin a 1 contents of six YM lines were in the range of 0.82-2.94 mg/g when assayed by the developed S-ELISA method. The results showed that S-ELISA could distinguish Sin a 1 in YM seed-derived extracts rapidly and could be applied in controlling and/or monitoring of YM allergenic proteins.