Role of secondary structures in the gelation of porcine myosin at different pH values.

Secondary structures, gelation properties and their relationships in porcine myosin were studied by circular dichroism, dynamic rheological measurement and scanning electron microscopy. Gelling of porcine myosin involved a change in myosin conformation with protein-protein and protein-water interactions. The gelation properties were strongly pH and temperature dependent. Near the pI (pH 5.5 and 6.0), porcine myosin could spontaneously coagulate at 15°C resulting partially from the presence of more β-sheets. Myosin at pH6.5-9.0 began to form a gel at temperatures greater than 38°C. Heating caused α-helices to partially turn into β-sheets and random coils. Subsequently, myosin aggregated and formed a gel network. The gel strength decreased and the water-holding capacity (WHC) increased with increasing pH. Correlation analysis indicated that both the unfolding of α-helices and the formation of β-sheets favored the gelation of porcine myosin. A high β-sheet fraction prior to heating resulted in a low WHC of resultant gel. A compact and uniform gel was also obtained at pH6.5.