Nutritional profiling and stability analysis of selected microalgae

Microalgae are emerging as a valuable source of nutrients and bioactive compounds1, offering substantial potential for applications in food2. This study provides a comprehensive biochemical characterisation of several microalgae species, including Chaetoceros calcitrans, Cylindrotheca fusiformis, and Nannofrustulum shiloi, focusing on protein content, mineral composition, amino acid profile, and shelf-life stability. In terms of protein content, Chaetoceros calcitrans exhibited the highest concentration at approximately 42% (w/w), followed by Cylindrotheca fusiformis and Nannofrustulum shiloi, which had protein contents of around 31% (w/w) and 27% (w/w), respectively. These findings highlight relevant protein levels and significant variations among different microalgae species, necessitating future studies on their quality and bioavailability. Mineral analysis revealed that Nannofrustulum shiloi contains about 70% calcium. Additionally, this microalgae is rich in sodium (Na), potassium (K), magnesium (Mg), and iron (Fe). Importantly, no heavy metals were detected in any of the analysed species, confirming their safety for food applications. Amino acid profiling of lyophilised biomass from Chaetoceros calcitrans and Cylindrotheca fusiformis showed high concentrations of essential amino acids, including leucine, isoleucine, methionine, phenylalanine, and threonine (ranging from 1.10 to 8.42 g/100 gDW). Shelf-life assessments revealed that Nannofrustulum shiloi maintained a stable amino acid composition over time, with only minor variations between the initial (T0) and subsequent (T2) storage periods (October 2023 and April 2024, respectively), suggesting that the dried biomass of this species retains its nutritional properties during extended storage. Conversely, Cylindrotheca fusiformis displayed notable changes in amino acid levels after storage, indicating that storage conditions can significantly affect its protein composition. These results underscore the nutritional potential and stability of certain microalgae species, particularly Nannofrustulum shiloi, for food applications. The observed variations in protein and amino acid profiles across species provide valuable insights for the development of functional food ingredients derived from microalgae.