Evaluation of extraction solutions for biochemical analyses of the proteins in rice grains.

The influence of different extraction solutions on the proteins extracted from rice grains was investigated. The largest amounts of salt-soluble proteins were extracted with solutions supplemented with Tris-HCl at pH 8.0. Rice allergens were analyzed by multiplex immunodetection. Except for α-globulin extracted with the solutions at pH 8.0, which showed a low-molecular-weight band besides the main band, no significant solution-dependent difference among the allergens was found. Total proteins were extracted with four kinds of solution. The extraction of the basic subunit of glutelin was found to be SDS-dependent, and more protein was obtained with extraction solutions supplemented with SDS. The contents of α-globulin and α-amylase/trypsin inhibitors were higher in the extracts without SDS than with SDS. We conclude from the present data that, in order to obtain comparable data from rice grain salt-soluble and total protein analyses, differences in the protein extraction efficiency of solutions used should be taken into consideration.