Thermal denaturation of porcine myofibrillar proteins at different heating temperatures: A focus on the surface hydrophobicity

Changes in the hydrophobic interactions of porcine myofibrillar proteins (MPs) were investigated at various heating and internal temperatures (ITs). MP extracts were heated at 50, 60, 70, 80, or 90 °C until their ITs reached the same respective values (±2 °C) and were labeled IT50, IT60, IT70, IT80, and IT90. The intrinsic tryptophan fluorescence intensity (FI) of the MPs decreased after heating at all ITs (<i>P</i> < 0.05). FI_max decreased significantly between IT50 and IT60 (<i>P</i> < 0.05) and increased from IT70 onward (<i>P</i> > 0.05), with IT80 and IT90 exhibiting higher FIs than IT60 (<i>P</i> < 0.05). Surface hydrophobicity increased at IT50 (<i>P</i> < 0.05), decreased at IT60 (P < 0.05), and peaked at IT80-IT90 (P < 0.05), compared with unheated MP. Fluorescence and confocal laser scanning microscopy images revealed a considerable aggregation increase from IT60, with notable exposure of the non-polar regions at IT60-IT90. Consequently, increased surface hydrophobicity remained even after MP coagulation when IT exceeded the myosin denaturation temperature.