Abstract: A large number of fish species exhibit protease activity and are therefore unacceptable for preparing processed fish products such as surimi. The present invention is directed to a composition containing alpha-2-macroglobulin for inhibiting protease activity contained in the fish material during the preparation of a processed fish product. Thus, the invention provides suitable protease inhibitors to treat a number of fish species which were previously unsuitable for preparing processed fish products such as surimi.The present invention also relates to a method of preparing a processed fish product comprising contacting the fish material with alpha-2-macroglobulin in an amount sufficient to neutralize or inhibit the protease contained in the fish material.In addition, the present invention is directed to a fish product prepared using the composition of this invention and to a fish product prepared according to the method of this invention.