Physicochemical Properties of Whey-Protein-Stabilized Astaxanthin Nanodispersion and Its Transport via a Caco-2 Monolayer

Astaxanthin nanodispersion was prepared using whey protein isolate (WPI) and polymerized whey protein (PWP) through an emulsification evaporation technique. The physicochemical properties of the astaxanthin nanodispersion were evaluated, and the transport of astaxanthin was assessed using a Caco-2 cell monolayer model. The astaxanthin nanodispersions stabilized by WPI and PWP (2.5%, w/w) had a small particle size (121 +/- 4.9 and 80.4 +/- 5.9 nm, respectively), negative zeta potential (-19.3 +/- 1.5 and 35.0 +/- 2.2 mV, respectively), and high encapsulation efficiency (92.1 +/- 2.9 and 93.5 +/- 2.4%, respectively). Differential scanning calorimetry curves indicated that amorphous astaxanthin existed in both astaxanthin nanodispersions. Whey-protein-stabilized astaxanthin nanodispersion showed resistance to pepsin digestion but readily released astaxanthin after trypsin digestion. The nanodispersions showed no cytotoxicity to Caco-2 cells at a protein concentration below 10 mg/mL. WPI-and PWP-stabilized nanodispersions improved the apparent permeability coefficient (P-app) of Caco-2 cells to astaxanthin by 10.3-and 16.1-fold, respectively. The results indicated that whey-protein-stabilized nanodispersion is a good vehicle to deliver lipophilic bioactive compounds, such as astaxanthin, and to improve their bioavailability.