Temperature-mediated assembly of quinoa protein-κ-carrageenan soluble complexes for stabilizing high internal phase emulsions to improve the intestinal targeted delivery of curcumin.
Temperature is a key factor regulating the assembly and functional properties of protein-polysaccharide complexes. In this study, curcumin-loaded high internal phase emulsions (HIPEs) were fabricated using quinoa protein-κ-carrageenan (QPI-κC) soluble complexes treated at temperatures ranging from 45 to 75 °C as stabilizers. Results indicated that oil phase screening showed rapeseed oil had the best curcumin solubility, while HIPEs prepared with soybean oil displayed uniform fine droplets and optimal stability. Moreover, moderate heat treatment (55 °C) endowed curcumin-loaded HIPEs with superior shear-thinning behavior, an elasticity-dominated gel structure, and the highest creep resistance and structural tolerance. Stability tests confirmed that after 35 days of storage, the HIPEs of the QPI-κC-55 °C group achieved the highest curcumin retention rate and degradation half-life at 25 °C (W = 59.73%, t = 32.89 days) and 4 °C (W = 72.40%, t = 44.12 days). Meanwhile, these HIPEs remarkably prolonged the degradation half-life of curcumin under high-temperature (t = 5.24 h) and ultraviolet irradiation (t = 5.75 h) conditions. During in vitro digestion, the intact interfacial barrier enables controlled lipolysis, yielding the highest free fatty acid release and curcumin bioaccessibility (59.73%). Thus, appropriately heat-treated QPI-κC complexes offer a synergistic plant-based platform for the encapsulation, protection, and intestinal delivery of hydrophobic bioactives.