Stabilization of beta-lactoglobulin by polyols and sugars against temperature-induced denaturation involves diverse and specific structural regions of the protein

Temperature sensitivity of bovine milk beta-lactoglobulin (BLG) was assessed in the presence/absence of non-reducing sugars (sucrose and trehalose) and polyols (glycerol and sorbitol). None of them affected the structural features of the protein at room temperature, where the only observed effect was an increased affinity towards hydrophobic probes in the presence of all co-solutes but glycerol. Although most of the observed effects in temperature-ramp experiments are due to entropic effects (fitting within the ‘‘preferential exclusion” theory of protein stabilization), this study indicates that each co-solute exhibit different efficacy at stabilizing specific regions of BLG, suggesting that each of them acts in a specific way on the solvent/protein system. The relevance of these observations with respect to systems of practical relevance is discussed, given the widespread use of heat-polymerizing proteins – such as BLG – in many food formulations that very often include significant amounts of sugars and/or polyols.