Valorization of soursop (Annona muricata) seeds as alternative oil and protein source using novel de-oiling and protein extraction techniques

In this research, for the first time, the valorization of soursop seeds, a poorly studied biomass, was investigated to simultaneously produce oil and proteins within a biorefinery approach. A new mild protein extraction method (Pressurized Water Extraction, PWE) was developed and optimized via response surface methodology and compared with conventional alkaline extraction. Furthermore, the impact of the de-oiling technique, i.e., n- hexane or cold pressing, was investigated. The extracted proteins were evaluated in terms of physicochemical composition, amino acid content, and techno-functional properties. The type of de-oiling technique was found to have a minor impact. Instead, considerable differences were observed between the two protein extraction methodologies. At optimized conditions (pH 8.1 and 40 degrees C), PWE resulted in a more protein-rich extract (48 vs. 30 wt% for alkaline water), better preservation of the amino acid content, and higher solubility and in vitro digestibility. A mixed behavior was found for the techno-functional properties. Emulsification and oil holding capacity were similar for both techniques, while improved foaming was observed after alkaline water extraction. This research showed that the non-exploited soursop seeds could be a valuable source of oil and protein. Moreover, the novel PWE enables protein extraction with reduced impact on the protein structure.

Automated summary

This research investigated the valorization of soursop seeds to produce oil and proteins. A new mild protein extraction method (Pressurized Water Extraction, PWE) was developed and optimized, and compared with conventional alkaline extraction. The impact of the de-oiling technique was also investigated. The extracted proteins were evaluated in terms of physicochemical composition, amino acid content, and techno-functional properties.