Effects of Sodium Chloride, Phosphate, and Dextrose on the Heat Stability of Purified Myoglobin, Hemoglobin, and Cytochrome c

Eight combinations of sodium chloride (0, 2.5%), sodium tripolyphosphate (0, .5%) and dextrose (0, 1%) were dissolved in phosphate buffer containing .5 mg myoglobin (Mb), hemoglobin (Hb), or cytochrome c per milliliter. These solutions were heated to 68 C, 74 C, 80 C, or 85 C to determine ingredient effects on the heat stability of purified Mb, Hb, and cytochrome c. Salt significantly decreased the heat stability of Mb at all temperatures studied, and Hb at 68 C and 74 C. However, salt significantly increased the heat stability of cytochrome c. Phosphate increased the heat stability of Mb but decreased that of cytochrome c due to a pH increase. Dextrose increased the heat stability of Hb at 68 C, and that of cytochrome c at 85 C.