Assessing the heat induced changes in major cow and non-cow whey proteins conformation on kinetic and thermodynamic basis

Abstract

In this study, the RP-HPLC technique was used as the main analytical method to measure the residual native β-lactoglobulin and α-lactalbumin concentration after heat treatment in raw milk from three different species (goat, sheep and cow). Further, a detailed comparative kinetic study of β-lactoglobulin and α-lactalbumin denaturation was carried out at temperature ranging from 72.5 to 90°C.Kinetic studies showed that the thermal denaturation of β-lactoglobulin followed biphasic behavior, resulting in activation energy of 91.68±13.18kJmol−1, 137.13±25.25kJmol−1 and 62.11±3.26kJmol−1 for the denaturated fraction in goat, sheep and cow milk and 307.91±61.29kJmol−1, 158.99±23.64kJmol−1 and 170.18±43.61kJmol−1 for the native fraction in milk samples. α-Lactalbumin denaturation followed the first-order kinetics, resulting in activation energy values of 202.65±1.42kJmol−1, 155.56±5.53kJmol−1 and 140.44± 6.14kJmol−1 respectively in goat, sheep and cow milk. The heat-induced changes in protein structure were outlined after running molecular dynamics simulations at different temperatures, supporting the experimental observations. These experiments were conducted only for cow and goat α-lactalbumin and were limited by the lack of protein structures from databases.