RAG2 is a member of the rice 14-16 kDa α-amylase/trypsin inhibitors, which are the main allergens in rice grains. Recombinant RAG2 protein was expressed in Escherichia coli, and polyclonal antisera were prepared against the protein. The polyclonal antisera specifically bound with 14-16 kDa α-amylase/trypsin inhibitors from husked brown, red and black rice. No cross-reaction was observed between the polyclonal antisera and saline-soluble proteins from other tested cereal grains. By immunoblotting with the polyclonal antisera, 14-16 kDa α-amylase/trypsin inhibitors were found to be distributed throughout the endosperm of brown rice and their contents were estimated. Moreover, 14-16 kDa α-amylase/trypsin inhibitors were also detected in processed foods. Thus, the polyclonal antisera prepared against recombinant RAG2 protein could be used to compare the content of 14-16 kDa α-amylase/trypsin inhibitors in rice samples and probe the presence of the allergen in processed foods.