The Comparative Heat Stability of Bovine β-Lactoglobulin in Buffer and Complex Media

The heat stability of β‐lactoglobulin (β‐lg) is usually described with reference to a concentration‐dependent pseudo‐rate constant k. Kinetic and thermodynamic parameters for the irreversible denaturation of β‐lg, in a whey protein mixture dissolved in Tris‐HCl buffer, were examined over a wide temperature range 75–120°C and for degrees of denaturation [(Co‐Ct)/Co] up to about 90%. The first‐order kinetic model best described β‐lg denaturation over the temperature range 75–85°C, whereas the second‐order model applies in the range 90–120°C. A comparison between β‐lg thermostability in buffer and literature data pertaining to more complex heating media (whey and milk), over the range 75–120°C, was carried out on the basis of changes in activation free energy (ΔG#), which itself takes into account changes in both activation enthalpy (ΔH#) and activation entropy (ΔS#). It was found that the thermal stability of β‐lg in different media, and irrespective of the kinetic model assumed in the present study, can be ranked: buffer ≪ whey>milk for the temperature range 75–85°C. On the contrary, at the higher temperature range, 90–120°C, the ranking is buffer