Composition and rheological properties of microalgae suspensions: Impact of ultrasound processing

Abstract

In this study the rheological properties of aqueous suspensions of three microalgae species, Nannochloropsis gaditana, Scenedesmus almeriensis and Spirulina platensis, were investigated as a function of solids content, and related to their composition and microstructure. In addition, the impact of ultrasound processing on their structuring ability was also studied. The less rigid character of the Spirulina platensis cell walls (with very low carbohydrate contents) and the presence of extracellular components promoted cell-cell interactions, yielding suspensions which showed a shear thinning behaviour at lower concentrations than Nannochloropsis gaditana and Scenedesmus almeriensis. It is noteworthy that the three species showed different viscoelastic properties at 25 wt. % total solids. Spirulina platensis suspensions showed a more elastic behaviour and lower frequency dependence, characteristic of weak gels, whilst Nannochloropsis gaditana and Scenedesmus almeriensis behaved more like viscous liquids. The ultrasound treatment did not affect the cell wall integrity, but it promoted the release of intracellular components (some of which could have been partially degraded) and disrupted physical interparticle interactions in Nannochloropsis gaditana and Scenedesmus almeriensis. This has an impact on the rheological properties, increasing the viscosity of Nannochloropsis gaditana suspensions, while the viscosity of Scenedesmus almeriensis suspensions was reduced. The outcomes of this work give insights into the exploitation of these microalgae species in soft materials for food, pharma and other technological applications.

Ultrasound Extraction Mediated Recovery of Nutrients and Antioxidant Bioactive Compounds from Phaeodactylum tricornutum Microalgae

“…This is in close agreement with the results reported by Parniakov et al [17] for Nannochloropsis spp., who found that the optimal extraction of the total phenolic compounds assisted by ultrasound (W= 400 W) was achieved after 15 min. Martínez-Sanz et al [31] also found a huge increase in the TPC extraction from Nannochloropsis gaditana, Scenedesmus almeriensis and Spirulina platensis after ultrasound treatment for 5 min. The temperature and pH did not significantly influence the polyphenol extraction (p = 0.5568 and 0.2021, respectively).…”

Evaluation of the bioprotective potential of gastrointestinal digest fractions of Arthrospira sp. and Nannochloropsis sp. suspensions treated with high pressure homogenisation

“…Sonication had dissimilar effects dependent on the microalgal species, wherein increased antioxidant activity was reported for A. platensis but reduction for N. gaditana and S. almeriensis . 50 Antioxidant activities as impacted by HPH appear to be more differentiated by their ferric reducing capacities. The limited consequence of homogenising pressure on the microalgal digest suspensions was comparable for the DPPH radical scavenging activities and total phenolic contents.…”

“…32 Due to the antioxidant potential being linked to the presence of polyphenols and other bioactive compounds in a complex mechanism, a link between the antioxidant capacity of samples and the release or degradation of specific components could not be explicitly made. 50 Other variables that could influence the antioxidant capacities and radical scavenging activities of microalgae are solvent polarity and dose-dependency. 32,51–53…”

Emergent Proteins-Based Structures—Prospects towards Sustainable Nutrition and Functionality

“…Microalgae suspensions may present different rheological properties depending on the microalgae strains and its cell properties, such as cell wall composition and structure [98]; in this respect, downstream processing such as US can disrupt cells' clusters or promoting release of intracellular components changing the rheological properties of microalgae suspensions [99]. Bertsch et.…”