Non-covalent interaction and digestive characteristics between α-lactalbumin and safflower yellow: Impacts of microwave heating temperature

Change in conformational and digestive properties of α-lactalbumin (α-LA) induced by safflower yellow (SY) in combination with microwave (MW) heating treatment (70, 80, 90 °C, 10 min) was investigated. Fluorescence study showed that the binding affinity of SY for α-LA increased with temperature. Meanwhile, the quenching mode of SY to α-LA intrinsic fluorescence was static, its binding constant to α-LA was enhanced with increasing temperature. The major interaction forces in α-LA-SY complexation contained hydrophobic force and hydrogen bond. Fourier transform infrared revealed that binding of SY altered α-LA conformation, and increasing MW temperature could have a boost effect on the conversion of α-helix and β-sheet to random coil and β-turn. In addition, SY had a little inhibiting influence on α-LA in vitro digestibility and degree of hydrolysis, while MW heating facilitated those of α-LA-SY complex. Moreover, antioxidant capacities of α-LA-SY complexes was enhanced as a function of temperature. Therefore, increasing MW temperature could facilitate non-covalent interaction (α-LA and SY) and improve α-LA digestibility and antioxidant capacities. These findings were helpful to better recognize α-LA structure and functionality as well as keep SY biological activity by controlling the processing temperature, providing a theoretical data of functional dairy-based products in food industry.