Determination of the modori phenomenon and its origin in surimi of five fish species from the Gulf of Mexico

Abstract

Modori is a phenomenon which occurs in fish gels only when they are incubated at 50-70 degrees C, and which induces a decrease in their mechanical properties. Modori has been associated with endogenous proteases, varying among fish species. Surimis were obtained from Atlantic croaker (Micropogon undulatus), barred grunt (Conodon nobilis), sole (Cyclopsetta chittendeni), northern kingfish (Menticirrhus saxatilis) and striped searobin (Prionotus evolans). The effect of gel incubation time on shear stress and shear strain at failure, soluble peptides and electrophoretic pattern was studied. Incubation times at 60 degrees C, of 0, 20 or 40 min were assayed. The modori phenomenon induced a significant decrease (25-50\%) in the mechanical properties of the five species studied. This phenomenon was associated with the presence of active proteases at 60 degrees C, determined as an increase in concentration of soluble peptides depending on the time of incubation. Proteases were partially characterized employing serine- and cysteine-protease inhibitors. The studies with SDS-PAGE showed that myosin is the main substrate of the proteases. Actin was not hydrolyzed. The employment of specific inhibitors showed that both serine- and cysteine-proteases were associated with the modori phenomenon in the species studied.