Thesis (M.Eng.)--Chulalongkorn University, 2006

Astaxanthin is receiving commercial interest due to its use as a preferred pigment in aquaculture feeds. Its anti-oxidant activity is approximately 100 times higher than that of Beta-tocopherol, and can be used as a potential agent against cancer. Astaxanthin can easily be degraded by thermal or oxidative processes during the manufacture and storage. In this study, astaxanthin and its biological activity were protected against oxidative environmental conditions by encapsulating the homogenized cells in chitosan, a nontoxic and biodegradable natural polymer. H.pluvialis was formed into beads, which were then coated with 5 layers of chitosan film. The efficiency of this technique of encapsulation was as high as 99% and the resulting chitosan capsules have the mean diameter of 0.43 cm and the total film thickness of approximately 100 micrometres. No significant loss in the amount of astaxanthin content in H.pluvialis was found due to the process of encapsulation. However, approximately 3% loss of antioxidant activity of the H.pluvialis was observed after encapsulation. For the study of stability under different storage conditions, the best storage condition was found to be at -18 degree Celsius under nitrogen atmosphere in the dark. Results from this study showed that although encapusulation caused 3% loss of antioxidant activity, the longer term stability study of the dried algae biomass, beads, and capules under different storage conditions indicated that encapsulation of H.pluvailis in chitosan film was capable of protecting the algae cells from oxidative stresses.