Arthrospira platensis (spirulina) is considered a source of natural molecules with nutritional and health benefits. As the different storage forms can affect the quantity and quality of bioactive ingredients, the aim of the present work was to evaluate the effects of freezing, oven-drying and freeze-drying on chemical composition of spirulina biomass. Total proteins, photosynthetic pigments and antioxidants, were analyzed and compared to respective quantities in fresh biomass. The frozen sample exhibited the highest content of phycocyanin-C, phenols, and ascorbic acid, also respect to the fresh biomass. The highest total flavonoid amount was in the freeze-dried biomass. HPLC-DAD analysis of phenolic acids revealed the presence of the isoflavone genistein, known for its therapeutic role, in all the spirulina samples. The phosphomolybdenum method (TAC) and DPPH scavenging activity were applied to determine the antioxidant activity of different samples. The highest DPPH scavenging activity was detected in fresh and freeze-dried biomass and it was positively related to carotenoid content. A positive correlation indicated that carotenoids, chlorophyll, ascorbic acid and all phenolic compounds were the major contributors to the TAC activity in spirulina biomass. The results highlighted a different functional value of spirulina biomass, depending on the processing methods used for its storage.
Keywords: Artrospira platensis; bioactive compounds; storage methods.