Comparative Analysis of Different Drying Techniques Based on the Qualitative Characteristics of Spirulina platensis Biomass

ABSTRACT

Over the last years, the cyanobacteria Spirulina platensis (SP) has attracted special attention, as it possesses remarkable antioxidant activity and high amounts of bioactive compounds, such as phycocyanin, carotenoids and phenolics. Since Spirulina platensis biomass shows extremely high moisture content, dehydration is a crucial treatment step, which ensures the prolonged shelf life of the final product. However, drying affects drastically the qualitative characteristics of heat-sensitive foodstuffs with high nutritional value, such as SP. In this study, four different drying techniques, atmospheric drying (AD), freeze drying (FD), vacuum drying (VD) and accelerated solar drying (ASD), were examined and compared considering crucial parameters, i.e., moisture content reduction, change of structure, colour deterioration, pigment content and antioxidant activity. As shown from the obtained results, vacuum drying achieves faster moisture lowering and higher carotenoid content equal to 0.58 + 0.01 mg (g dry solids)⁻¹. On the other hand, atmospheric drying is efficient in preserving phycocyanin since its content was found equal to 9.65 + 0.19%dry weight, but in general cannot be industrially applied due to the long dehydration time. Finally, accelerated solar dried biomass showed the highest antioxidant activity (31.28 ± 0.90% dry weight) mainly due to the degradation products after heating at high temperatures and stress conditions.

KEYWORDS:

• Freeze drying
• vacuum drying
• phycocyanin
• phenolics
• carotenoids