Characterisation of protein isolates and oleosomes extracted from cryo-milled quinoa seeds

Quinoa is a pseudocereal with a complete essential amino acid profile and nutritionally favourable fatty acid composition. Here, cryo-milling was used to disrupt quinoa seeds, promoting the preservation of the native oleosome structure, which was then recovered by centrifugation of the cryo-milled seed suspension. The remaining flour suspension was used to extract quinoa protein isolate; applying alkalinisation followed by precipitation with HCl, acetic acid or citric acid. Microscopy, droplet size and ζ-potential data indicated recovered oleosomes were predominantly in their native state, which was retained after acid treatment. Quinoa protein precipitated with citric acid showed a higher denaturation enthalpy compared to protein precipitated with HCl or acetic acid. The citric acid-based protein gel also had the highest final gel strength and showed a fine stranded microstructure, while the HCl-based protein gel had the lowest final gel strength and displayed a particulate microstructure. Treatment with acetic acid gave a protein gel that demonstrated a mix of both types of microstructures. This study not only introduces quinoa seed oleosomes and quinoa protein isolate with improved and tailored functionality but also demonstrates the potential of cryo-milling as a seed disruption technology that allows recovery of intact oleosomes.