Astaxanthin-containing hollow salt derived from Haematococcus pluvialis protein-chitosan complex with strong antioxidant capacity as a promising salt substitute

Excessive dietary sodium chloride (NaCl) intake is strongly associated with hypertension and an elevated risk of stroke and cardiovascular disease. In this study, astaxanthin-containing hollow salt was prepared using a spray-drying method from an emulsion containing a high concentration of NaCl, stabilized by a complex of Haematococcus pluvialis protein (HPP) and chitosan (CS). The interaction between HPP and chitosan, as well as the effects of varying concentrations of HPP-CS complexes on salt emulsion, were investigated. The HPP-CS complex at a ratio of 1:2 and pH 5 exhibited strong binding and emulsifying abilities. Cryo-scanning electron microscopy revealed that emulsions stabilized by the HPP-CS complex exhibited smaller particle sizes and a more uniform distribution. As the HPP-CS complex concentration increased, the emulsion exhibited higher structural stability, excellent fluidity, and improved thermal stability. The stability of emulsion was significantly improved by HPP-CS complex. These results confirmed the potential application of salt emulsion stabilized by HPP-CS complex in hollow salt preparation. Hollow salt prepared by spray drying exhibited a smooth surface, uniform particle size distribution, and microspheres with a diameter of less than 10 μm. The hollow salt had a sodium content of 0.22 g per gram. Sensory evaluation and electronic tongue results showed that there was no significant difference in saltiness between hollow salt and traditional NaCl under the same mass. High astaxanthin retention and oxidation stability during storage at 50 °C for 15 days were observed in the hollow salt. In addition, the protective effect on fried steaks stored overnight revealed that the astaxanthin-containing hollow salt significantly reduced the lipid hydroperoxide and malondialdehyde content. Therefore, the hollow salt, based on an emulsion stabilized with the HPP-CS complex, may serve as a potential low-salt substitute and dietary supplement.