Effect of heat pre-treatment on interaction between micellar casein and betanin, and characteristics of their complexes.

Betanin (BT), a natural red pigment, has faced application limitations due to its inherent instability. This study conducted a comprehensive evaluation of micellar casein (MC) as a natural carrier for BT. The findings revealed that primary interactions between MC and BT involved hydrogen bonding and van der Waals forces under conditions of 45 °C or 55 °C pre-heating or no pre-heating, which shifted toward electrostatic forces at 65 °C. After 55 °C pre-heating, MC-BT exhibited the highest binding constant [(9.96 ± 0.85) × 103 L·mol-1], alongside a more ordered conformation. Loaded BT with MC pre-heated at 55 °C significantly enhanced thermal and pH stabilities, boosted antioxidant activity of BT and hindered the release of BT in simulated gastric fluid. By the end of 3-h intestinal digestion, the cumulative release reached 50.32 ± 0.63% for free BT but soared to 89.33 ± 0.81% for MC-BT after pre-heating at 55 °C.