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The possible effect of the proteolytic activity on emulsifying properties of squid ( Illex argentinus ) mantle actomyosin stored at 2-4°C and the effects of cocktail of protease inhibitors [phenylmethylsulfonyl fluoride (PMSF), iodo acetic acid (IAA) and ethylene diamine-tetra acetic acid (EDTA)] were investigated. Oil/water emulsion and their stability were studied by optical characterization using a vertical scan analyzer. The particle size distribution of emulsions was obtained with a particle analyzer. O/W emulsions formulated with actomyosin of squid mantle with inhibitors showed certain stability during the first 15-20 min, and then destabilize during the analyzed remaining time, reaching BS (Backscattering) of approximately 20% with no significant changes thereafter. However, in emulsions formulated with actomyosin without inhibitors, the decrease in BS was recorded at 30-40 min, indicating a greater stability, as a function of the storage time, in comparison with those in presence of inhibitors actomyosin. The particle size distribution of both emulsions presented, for actomyosin with and without inhibitors, three droplet populations at zero time. Greater droplet size, De Brouker mean diameter D [4.3], was observed for either emulsions formulated with actomyosin without and with inhibitors, at 24 and 48h of storage. The addition of SDS solution led to a reduction of the population of large particles suggesting the presence of stable flocs under the analyzed conditions. In addition, the P (polidispersity) values corresponding to actomyosin without inhibitors were significantly (p < 0.05) higher than those of actomyosin with inhibitors. Both emulsions exhibited a significant destabilization by creaming and flocculation. The stability of emulsions was enhanced when aggregates appeared in emulsions, mainly for emulsions stored without inhibitors. These results suggest that the proteolytic activity can favour the emulsifying properties of actomyosin obtained from squid mantle stored at 2-4°C. The structure of flocs would affect positively the stability of O/W emulsions.