Thermal Denaturation of Myofibrillar Proteins of Striated and Smooth Adductor Muscles of Scallop (Zygochlamyspatagonica). A Differential Scanning Calorimetric Study

Denaturation of proteins from striated and smooth muscles of scallop (Zygochlamys patagonica) was studied with differential scanning calorimetry (DSC) by monitoring maximum temperatures of transition and denaturation enthalpies. DSC thermograms of both striated and smooth whole muscles showed two transitions: Tmax 55.0, 79.2 °C; and Tmax 54.7, 78.7 °C, respectively. The DSC thermograms of myofibrils and actomyosin were similar to those corresponding to their respective whole muscles. As pH and ionic strength increased, the thermal stability of whole muscles decreased. The pH increase (5.0−8.0) significantly (p < 0.01) decreased the denaturation enthalpies (ΔH total, ΔH peakI, and ΔH peakII) of whole striated muscles. A significant decrease (p < 0.05) in the ΔH total and the ΔH peakI was also observed in DSC thermograms of smooth muscles at pH 8.0. Denaturation enthalpies (ΔH total and ΔH peakI) significantly decreased (p < 0.01) when the ionic strength increased from 0.05 to 0.5 in both types of muscles. Striated muscles were more affected than smooth muscles by changes in the chemical environment. Keywords: Thermal denaturation; myofibrillar proteins; Patagonian scallop