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

Abstract

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 °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.