Optimization of wall material selection and preparation process for the microencapsulation of algal oil-derived docosahexaenoic acid

Docosahexaenoic acid (DHA) derived from algal oil is vital for human health; however, its high susceptibility to oxidation limits its direct application in food systems. Microencapsulation is an effective strategy to improve DHA stability, and the selection of appropriate wall materials plays a central role in determining microcapsule quality. In this study, we evaluated the feasibility of using crosslinked sodium caseinate as a wall material for DHA microencapsulation. Emulsification properties, microencapsulation yield and efficiency, peroxide value, and release performance were also systematically assessed. The results indicated that crosslinked sodium caseinate effectively stabilised the emulsions and served as a suitable encapsulating material for algal oil-derived DHA. The resulting microcapsules exhibited high microencapsulation efficiency and yield, low surface oil content, and strong oxidative stability. However, microcapsule quality was influenced by the crosslinking reaction time, highlighting the importance of process optimisation. Comparative analysis showed that spray drying at an inlet air temperature of 185 °C produced superior microcapsules compared to that seen with freeze drying. Furthermore, the incorporation of β-cyclodextrin or trehalose as auxiliary materials enhanced the microcapsule quality and encapsulation efficiency. Under optimal conditions, solid concentration of 30 %, core material addition of 30 %, and homogenisation pressure of 30 MPa, the encapsulation efficiency exceeded 96 %. These findings provide valuable insights into the development of high-quality DHA microcapsules with enhanced stability and controlled release properties.