Production of Spirulina (Arthrospira platensis) powder by innovative and traditional drying techniques

Arthrospira platensis is a cyanobacterium used as food due to its high protein content and bioactive compounds (e.g., phycocyanin) and marketed mainly as a dried powder. Drying may cause quality degradation of Spirulina biomass, depending on the technique and the process conditions. In this study, thin layer drying (3 mm) of Spirulina suspension was performed by different techniques, comparing innovative and traditional driers. The innovative drying technique proposed in this study, called vacuum cast-tape drying (at 40 and 60 degrees C), was compared, in terms of drying kinetics and quality of the powders, to air drying (at 40 and 60 degrees C), freeze-drying, and cast-tape drying. Drying curves, the temporal evolution of water activity, and phycocyanin retention during drying were assessed. The microstructure and color of the powders were also determined in the dried powder. Cast-tape drying resulted in the highest drying rate but showed a very low (approximate to 10%) phycocyanin retention, while the other techniques allow phycocyanin retention >70%, regard to the raw biomass. The freeze-dried product presented a lighter color compared to the other techniques. Vacuum cast-tape drying showed a shorter drying time (90-180 min) than freeze-drying (720 min) and air drying (420 min), maintaining high phycocyanin retention (about 80-90%). Vacuum cast-tape drying is an efficient, suitable, and low-cost technique to dehydrate Spirulina at moderate temperatures in short times, maintaining the high quality in terms of bioactive compounds. Practical applications High-quality Spirulina powders are considered as potential future sources of protein and bioactive compounds. These components should be preserved during drying, necessary for the stabilization of this product. The novel drying technique proposed in this paper for Spirulina powder production is an alternative, low-cost, and potentially scalable technique for small and medium Spirulina producers. Vacuum cast-tape drying allows combining the efficiency of cast-tape drying with the vacuum atmosphere preserving the color and phycocyanin in the dried biomass. In this way, the study of novel drying processes for Spirulina powder production with high quality is of interest to researchers and the food industries.