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-freezedrying
(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.