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Actomyosin (AM) of mantle and fin from squid was stored at 2-4°C and the possible presence of proteolytic activity was investigated. Similar SDS-PAGE 10% patterns were obtained with both AM at zero time of storage. In absence of protease inhibitors, a decrease in the intensity of the band of the myosin heavy chain (MHC) and an increase in those of 155 kDa and 55 kDa bands of stored AM was observed. In presence of either PMSF (phenylmethylsulfonyl fluoride) or EDTA (ethylenediaminetetraacetic acid) both AM showed a minor degradation of the MHC, being the EDTA more effective. Proteolytic changes were accompanied by a significant increase (p < 0.05) in the proteinsurface hydrophobicity, (So: 1-anilino-8-naphtalene sulfonic acid (ANS)), the emulsion activity index (EAI) and the emulsion stability (ES) at 24 h of storage. At the same time, the reduced viscosity (VER) decreased significantly (p < 0.05). No significative changes (p > 0.05) in VER, IAE and ES of both AM occur in presence of protease inhibitors.A proteolytic activity closely associate with actomyosin from squid mantle and fin, was detected. Both serine and metalloproteinase activities were responsible for the autolysis of stored actomyosin. The best emulsifiying properties were obtained with AM without inhibitors. Because of this fins proteins could be and inexpensive source of functional ingredients with potential application as emulsifier agents in food product.

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