Impact of drying processes on the fatty acid composition of Chlorella vulgaris

Healthy fatty acids (FA) composition, namely, polyunsaturated fatty acids (PUFA), is one of the most interesting characteristics of microalgae in the development of new functional food products. In order to be more easily incorporated into different formulations, drying of the microalgae biomass can be performed. Freeze-drying is the most widely utilized methodology for drying microorganisms while spray-drying can be a faster and less expensive solution. The aim of this research work was to evaluate the effects of these two drying techniques on the yield and FA quantitative and qualitative profiles of harvested Chlorella vulgaris biomass. Results showed that the yield of C. vulgaris biomass powder was of almost 100% when obtained by freeze-drying, and only 40% when spray-drying was employed. Although the highest total FA concentration was found in the freeze-dried C. vulgaris powders, some FA were present in higher amounts in the equivalent spray-dried powders. However the most important FA compounds for human nutrition such as C18 : 2 c9c12 (linoleic acid), C18 : 3 c9c12c15 (a-linolenic acid) and C22 : 5 n3 (docosapentaenoic acid; DPA) were higher in the freeze-dried biomass powders: e.g. DPA concentration was two-fold higher in the freeze-dried powder than in the spray-dried counterpart. According to the results from this research, when PUFA content is concerned, freeze-drying is the best method to obtain algae powders from C. vulgaris.