Thermal gelation of brown trout myofibrils from white and red muscles: effect of pH and ionic strength

The effects of pH and ionic strength on the thermal gelation of brown trout myofibrils from white and red muscles were analysed by thermal scanning rheometry. The highest gelation ability was obtained at low pH (around 5.6) whatever the ionic strength. No effect of ionic strength was observed at pH 5.6; however, at pH 6.0, lowering the salt (KCl) concentration to 0.3 M or less improved the characteristics of the gels formed. The effects of pH and ionic strength on myofibrils from both muscle types appeared to be similar, but red muscle proteins were less sensitive to changes in their physicochemical environment. Consequently, the differences between muscle types appeared to be dependent on pH and ionic strength. Solubility measurements revealed large differences between muscle types and between different pH values. Ultrastructural observations confirmed that different kinds of gels were formed depending on the physicochemical conditions and muscle type origin. (C) 2002 Society of Chemical Industry.