Thermal Properties of Yak α-Lactalbumin and β-Lactoglobulin: a DSC Study

A differential scanning calorimetry (DSC) method was used to investigate the denaturation temperature of yak alpha-lactalbumin (alpha-La), beta-lactoglobulin (beta-Lg), and a mixture of two proteins and the thermal properties of alpha-La and beta-Lg in the presence of glucose, lactose, sucrose, NaCl, CaCl2, and at various pH (4.0-10.0). The denaturation temperature (T (d)) of alpha-La increased from 52.1 A degrees C in the absence of beta-Lg to 53.9 A degrees C in the presence of beta-Lg, while the T (d) of beta-Lg decreased from 81.4 A degrees C in the absence of alpha-La to 79.9 A degrees C in the presence of alpha-La. alpha-La was thermal stable in the range of pH 4.0-10.0, while beta-Lg was more thermal stable in acidic pH than in alkaline pH. Sugars, Na+, and Ca2+ influenced the stabilization of the two proteins against thermal denaturation with greatly influenced for beta-Lg. alpha-La kept reversibility in the presence of sugars, NaCl, CaCl2, and over a wide pH range (4.0-10.0), with most of the reversibility values being greater than 90%. In contrast, beta-Lg was completely irreversible whether in its native state or in the presence of the additives.