Microencapsulation of Docosahexaenoic Acid by Spray-Freeze-Drying Method and Comparison of its Stability with Spray-Drying and Freeze-Drying Methods

Producing docosahexaenoic acid (DHA) in powder form is a great challenge as oxidation of polyunsaturated DHA takes place during drying due to higher temperature operations. One solution to this problem is to microencapsulate the DHA, which may restrict the oxidation of polyunsaturated DHA. In this study, first time spray-freeze-drying (SFD) technique is used for microencapsulating DHA and compared the results with spray-drying (SD) and freeze-drying (FD) techniques. Emulsifier of Tween-40 yielded better stability in different emulsion stability studies. A study of Fourier transform infrared spectra confirmed the presence of DHA in all the microencapsulated samples. SFD method yielded microencapsulated DHA with lower peroxidation (protected from oxidation) than FD and SD methods due to low temperature operation. However, encapsulation efficiency (oil retention) of SFD microcapsules yielded slightly lower (71 %) than the SD (about 83 %) and FD (73 %) methods. The percentage of oxidation was lower (13 %) during SFD process, whereas higher in FD (31 %) and SD (33 %) processes. Storage study indicated that SFD microencapsulated powders showed lower peroxidation than FD and SD encapsulated powders. Moreover, morphology of spray-freeze-dried samples depicted spherical shape with fine pores on the surface, while spray dried process yielded spherical shape without pores, which in turn resulted in good rehydration behavior of the SFD powdered product.