Camel α−lactalbumin at the oil−water interface: Effect of pH and heat treatment on the structure, surface characteristics and emulsifying properties

The effects of pH (3.0, 6.0, 9.0) and heat treatment (25 °C, 65 °C, 95 °C) on the emulsifying properties of α−lactalbumin extracted from camel milk were investigated and compared to bovine α−lactalbumin. The results show that both studied proteins displayed a rather different evolution of their emulsifying activity as a function of the main factors (pH and temperature); however, they exhibited very close maximum values, between 100 and 110 m2 g−1. The stability of camel α−lactalbumin stabilised emulsions at pH 3.0 and 9.0 was attributed to the associated electrostatic forces (ζ−potential ~ −30 mV). The emulsifying properties of camel α−lactalbumin were less sensitive to heat treatment (95 °C), due to the higher conformational flexibility, as surface hydrophobicity increased with temperature (from 16 A.U to 51 A.U); conversely, bovine α−lactalbumin enhanced emulsion stability vs. pH and heat treatment, due to hydrophobic interactions and a more rigid molecular structure. Statistical tests also showed that the adsorption of camel α−lactalbumin at the oil−water interface was significantly affected by pH change.