Rheological parameters as predictors of protein functionality: A model study using myofibrils of different fibre-type composition.

The rheology of myofibrils from a typical red muscle, m. masseter, and a typical white muscle, m. cutaneus trunci, has been studied at different pH values and salt and myofibrillar-protein concentrations. The storage modulus G' and the phase angle δ were related to the parameters pH, salt, and muscle, by using partial-least-square-two-block modelling. At high and low temperatures, G' was largely affected by pH and salt, respectively. For δ, the reverse was observed. The peak G' observed at temperatures between 40 and 60°C is an indicator of salt addition above the physiological salt level for both types of myofibrillar system. The magnitude of the change in G' per degree, in the temperature range 40-60°C, was the most muscle-specific parameter observed, and the peak was larger for cutaneus trunci than masseter myofibrils. At high temperatures (80°C), the cutaneus trunci myofibrils, for technical relevant conditions, formed stronger gels than masseter myofibrils. The cutaneus trunci systems also aggregated more strongly and exuded more water than systems of masseter myofibrils. The effect of strain on G' was generally larger for cutaneus trunci than for masseter myofibrillar systems. Many observations on myofibrillar systems were transferable to real-meat systems, which were also examined.