Abstract: Use of purified L‐kininogen to prevent actomyosin (AM) degradation by cathepsins, and pig plasma proteins to reduce mackerel modori were investigated. Myosin heavy chain (MHC) degradation in AM containing various cathepsins was significantly inhibited by purified L‐kininogen. The texture of mackerel gel increased to 2‐fold and 1.7‐fold in breaking force (g) and deformation (cm) separately after adding 1% pig plasma protein. SDSPAGE showed that degradation of MHC in mackerel surimi was significantly reduced after 1% pig plasma protein addition at several temperatures. It suggested that the pig plasma protein containing L‐kininogen could effectively reduce the modori phenomenon of mackerel surimi during processing.