Structurability of microalgae, soy and pea protein for extruded high-moisture meat analogues

Despite ecological and nutritional benefits, food ingredients derived from microalgae remain a niche market. A contributing factor to this is the lack of knowledge to exploit their techno-functional properties. This research investigated the structurability of Auxenochlorella protothecoides microalgal biomass during high moisture extrusion cooking for meat analogues. The fibrous extrudate structure weakened with increasing A. protothecoides content in the recipe. To scrutinise reasons for this phenomenon, a thorough compositional comparison of microalgal biomass and conventional raw materials from soy and pea was performed. The identified macrocompositional differences were shown to exert only a minor impact on fibrous structure formation. Thus, structurability appears to be predominately influenced by protein composition, protein properties and electrolyte environment. The proteins of the analysed microalgal biomass were 20 % smaller in molecular weight, had 18-68 % higher solubility and contained 15-50 % less hydrophobic sidechains, all of which may impede protein interaction potential and thereby network formation. Additionally, the pH of microalgae suspensions was lower, which has a negative impact on disulfide bridge formation. Moreover, the analysed microalgal biomass contained considerable amounts of kosmotropic ions that stabilise individual proteins. Denaturation, pH shift, addition of cysteine, transglutaminase and polyvalent cations were proposed as measures to improve structurability of the microalgae A. protothecoides.