Abstract: Astaxanthin is a natural carotenoid pigment with a variety of bioactivities, but its poor water-solubility and high sensitivity to temperature or light limit its application. Recently, due to its pH-induced disassembly and reassembly property, ferritin, a cage-like protein, has emerged as a new vehicle for the encapsulation of various nutrients. However, during encapsulation, at least 40% of total proteins can be damaged because of harsh pH conditions. Therefore, in this study, an ultrasound-assisted approach was established for the successful encapsulation of astaxanthin within ferritin nanocages, without damage to the protein nanocages. Quantitative analysis by high performance liquid chromatography (HPLC) indicated that one ferritin molecule could encapsulate approximately 40 astaxanthin molecules. The results of light and thermal stability experiments showed that the degradation rate of astaxanthin was reduced from 45% at the end of heat treatment and 31% at the end of light treatment to 3% after being loaded into the protein cavity, respectively. As expected, the encapsulation of astaxanthin within ferritin nanocages pronouncedly improved its water-solubility and photothermal stability as compared to astaxanthin alone. The reported method provides new possibilities for encapsulating and delivering nutrients, thereby facilitating their applications in the food industry.

Key words: astaxanthin; ultrasound treatment; ferritin; encapsulation