Extraction of Oleosome and Protein Mixtures from Sunflower Seeds

Oil seeds contain 10-20 wt% proteins and up to 50 wt% oil, organised in micron-sized oil droplets, named oleosomes. During oil extraction, which takes place using mechanical pressing or organic solvents or a combi-nation of them, oleosomes are ruptured, and the oil is obtained. The oil extraction process might lead to the degradation of both the contained oil and proteins, therefore, as an effort to have a minimum impact on the quality of both, an aqueous extraction has been suggested, where oleosomes and proteins are simultaneously extracted. Oleosomes, being oil droplets themselves, can be used in emulsion-like food products, however, their extraction and purification from proteins is energy intensive. For a better understanding of the extraction and separation of oleosomes and proteins from sunflower seeds, we here explore the mass balance of oleosomes and proteins during each extraction step. Additionally, we investigate the effect of the process steps on oleosome physical stability. At the initial extract, oleosomes and proteins were at a 3:1 ratio, with an oleosome diameter of up to 10 & mu;m. Three centrifugation steps were needed to separate proteins since the cream obtained had an oleosome/protein ratio close to 20:1. However, the removal of proteins had a significant effect on droplet coalescence, since oleosomes with a diameter up to 40-50 & mu;m were observed. After a homogenisation step though, the oil droplets regained their initial size. Besides the effect on the physical stability of the sunflower oleosomes, the oleosome purification affected the obtaining yield, as from 87 wt% after the first extraction step, dropped to 66 wt%. By providing the mass balances during the oleosome/protein extraction from sunflower seeds, we highlight the effect of the sunflower oleosome purification steps on the obtaining yield and the role of the co-extracted storage proteins on their physical stability. Unlikely oleosomes from other sources, those derived from sunflower seeds, are prompt to coalescence when storage proteins are not present. With this insight, we provide tools for targeted sunflower oleosome and protein extraction depending on the potential applications and yield needed.