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The demand for natural foods with high protein content and functional properties is constantly growing in the last years. In this context, microalgae as Spirulina (Arthrospira spp.), Chlorella spp., Haematococcus pluvialis, Dunaliella salina, and others, assume a key role to diversify the offer of nutritious and functional ingredients and supplements. Microalgae are commercialized, mostly, as dried powders to facilitate their use as food ingredients and to allow easy transportation and long-term stability. Microalgal powder quality and storage stability depend mainly on drying method, packaging, and storage conditions. Most of the studies that approach the subject of microalgal drying evaluate the efficiency of the process and suitability for this raw material. However, studies that assess the effect of traditional and innovative drying methods on quality of microalgal powder for human consumption are rare in literature. In this chapter, the state of the art of drying processing technology for microalgae was reviewed, discussing the effect of dehydration on quality and stability of microalgal powders with potential use in human alimentation.

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 C), was compared, in terms of drying kinetics and quality of the powders, to air drying (at 40 and 60 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 (≈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 applicationsHigh-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.

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Summary In this work, the addition of pretreated Kappaphycus alvarezii flour to a rice‐based snack formulation was proposed as an alternative to producing algae‐enriched snacks adding value to this seaweed and improving the quality of the snacks. Dried algae were submitted to multiple washing cycles to allow the reduction of the natural salt concentration of the algae. After, algae were dried and milled to obtain flour. The flour was added in different concentrations (0%, 2%, 5%, and 10%) in the model formulation of rice‐based dough. Rice‐K. alvarezii snacks were produced by baking at 220 °C. The proximate composition of the raw and pretreated algae was determined, as well as the colour, texture, and microstructure of dough and snacks. The pretreatment efficiently allowed for a reduction of 78% of the initial content of sodium and an 85% reduction of potassium. The concentration of 5% and 10% of algae addition presented higher values of hardness and consistency of the dough and lower adhesiveness. At higher concentrations, the seaweed flour acts as a processing aid during the preparation steps of the snacks but does not influence the hardness of the final snacks. The pretreated K. alvarezii flour is an alternative for increasing the quality of rice‐based snacks while preserving the algae's potential health benefits.