A novel approach for the protein determination in food-relevant microalgae

Microalgae are gaining interest as food ingredient. Assessments of functional and nutritional properties are necessary to forward their implementation. In this study, protein content and composition of eight commercially available microalgae biomasses were determined and compared to conventional food proteins. A novel procedure for the determination of the true protein content was proposed: Multiplication of proteinic nitrogen with a sample-specific nitrogen-to-protein conversion factor kA. The proteinic nitrogen was derived from the difference of total nitrogen minus non-protein nitrogen. The average kA for microalgae was 5.3 and considerable variation between different microalgae biomasses were detected. In addition, the content of non-protein nitrogen varied between 3.4% and 15.4%. The amino acid profiles of Chlorella samples were nutritionally superior to the tested plant proteins but indicated lower protein interaction tendency, potentially limiting their structuring functionality. In contrast, Auxenochlorella contained lower amounts of indispensable amino acids while showing com-parable interaction potential to plant proteins.

Automated summary

This study determined the protein content and composition of eight commercially available microalgae biomasses and compared them to conventional food proteins. The results showed variations in protein content among different microalgae, with Chlorella having a superior amino acid profile in terms of nutrition but lower protein interaction ability, while Auxenochlorella had lower levels of essential amino acids but comparable interaction potential to plant proteins.