**4. Conclusions**

Microalgae are dried to allow easy storage and transportation as well as to facilitate their use in biorefinery and food and feed industry. In this chapter a concise overview of the state of the art about drying of microalgal biomass with potential use for human alimentation was presented. In literature, drying of algal biomass is approached, in most cases, focusing on energy efficiency and engineering of processes. Not much attention is given to the effect of dehydration on functional and nutritional components of the final product. Among the methods that are studied and applied to produce algal biomass for human use, spray drying is the most widely used; it is a very efficient method especially adequate for largescale producers. Although, this method allows producing powders with relatively high retention of functional components, it was demonstrated that the due to cell structure degradation that occurs during drying, these components can be lost during storage under inadequate conditions. The same problem was found in freeze-dried powders; however, freeze-drying allows higher retention of functional components immediately after drying; thus, with adequate storage condition, this can be considered the best method to maintain quality of biomass. On the other hand, this method is very expensive and energy costing and thus is adequate only to produce high added value products. Air-drying is one of the most studied methods, and it was proposed, when performed adequately, as a good method to allow quality retention in dehydrated products. For example, spreading of the moist biomass in a thin layer increases the evaporation rate allowing lower drying time and the use of lower temperature, thus allowing higher retention of functional components in the final products. Alternatives to this technology have been developed combining thin layer drying with a vacuum chamber allowing reducing drying temperature and time and obtaining higher-quality products. Air-drying or thin layer drier (air or vacuum) is, in general, less expensive than spray driers or freeze-driers, in terms of

**85**

**Author details**

Fábio de Farias Neves1

\*, Mariana Demarco2

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

2 Federal University of Santa Catarina, Florianópolis, Brazil

\*Address all correspondence to: fabio.neves@udesc.br

1 Santa Catarina State University, Laguna, Brazil

provided the original work is properly cited.

and Giustino Tribuzi<sup>2</sup>

*Drying and Quality of Microalgal Powders for Human Alimentation*

installation and operational costs, and thus is a better option for small-scale producers. Finally, it can be concluded that more studies are necessary to improve not only the drying methods but also to understand the degradative phenomena that occur during storage in particular with regard to the high sensitivity to light, heat, and oxygen of dried microalgal biomass, to allow providing the consumers high-quality

*DOI: http://dx.doi.org/10.5772/intechopen.89324*

products.

### *Drying and Quality of Microalgal Powders for Human Alimentation DOI: http://dx.doi.org/10.5772/intechopen.89324*

*Microalgae - From Physiology to Application*

Other technology that can be used to dehydrate viscous foodstuff is the refractance window drying [51] or the cast-tape drying [52–55]. In both methods the liquid food is spread on surface, and the heat transfer occurs by radiation or by conduction. These methods allow producing high-quality fruit pulp powder with very low processing time. On the other hand, the temperature used in these processes could be above the limit for functional component preservation in microalgal biomass; thus, a vacuum chamber can be coupled to the cast-tape drier, and lower processing temperature can be used [56]. The vacuum drying removes the sample moisture thru low atmospheric pressure, showing many advantages comparing the conventional drying methods, that is, oxidation reducing. The low pressure in the drying chamber substitutes the hot-air flow, avoiding significantly compound degradations that lead to low product quality [57, 58]. This technology has been studied recently to spirulina biomass with interesting results in terms of quality and processing time [59, 60]. The cast-tape drying method used in preliminary studies for spirulina biomass drying has proved to be a very effective method in terms of drying time and efficiency. Using the same principle (thin layer of sample on a heated surface), vacuum cast-tape drying allows drying at lower temperatures, thus avoiding the degradation of important compounds such as phycocyanin. Preliminary studies conducted by our group showed phycocyanin preservation values greater than 60% in the method using vacuum and milder temperatures. The authors showed and reported that this technology is a promising method, which can achieve excellent moisture and water activity values, better performance, and low

energy costs compared to conventional and/or expensive drying processes.

Microalgae are dried to allow easy storage and transportation as well as to facilitate their use in biorefinery and food and feed industry. In this chapter a concise overview of the state of the art about drying of microalgal biomass with potential use for human alimentation was presented. In literature, drying of algal biomass is approached, in most cases, focusing on energy efficiency and engineering of processes. Not much attention is given to the effect of dehydration on functional and nutritional components of the final product. Among the methods that are studied and applied to produce algal biomass for human use, spray drying is the most widely used; it is a very efficient method especially adequate for largescale producers. Although, this method allows producing powders with relatively high retention of functional components, it was demonstrated that the due to cell structure degradation that occurs during drying, these components can be lost during storage under inadequate conditions. The same problem was found in freeze-dried powders; however, freeze-drying allows higher retention of functional components immediately after drying; thus, with adequate storage condition, this can be considered the best method to maintain quality of biomass. On the other hand, this method is very expensive and energy costing and thus is adequate only to produce high added value products. Air-drying is one of the most studied methods, and it was proposed, when performed adequately, as a good method to allow quality retention in dehydrated products. For example, spreading of the moist biomass in a thin layer increases the evaporation rate allowing lower drying time and the use of lower temperature, thus allowing higher retention of functional components in the final products. Alternatives to this technology have been developed combining thin layer drying with a vacuum chamber allowing reducing drying temperature and time and obtaining higher-quality products. Air-drying or thin layer drier (air or vacuum) is, in general, less expensive than spray driers or freeze-driers, in terms of

**84**

**4. Conclusions**

installation and operational costs, and thus is a better option for small-scale producers. Finally, it can be concluded that more studies are necessary to improve not only the drying methods but also to understand the degradative phenomena that occur during storage in particular with regard to the high sensitivity to light, heat, and oxygen of dried microalgal biomass, to allow providing the consumers high-quality products.
