High-intensity ultrasound affects the physicochemical, structural and functional properties of proteins recovered from noni (Morinda citrifolia) seeds

Recently, fruit seeds have been considered as an alternative source of protein with the potential to replace those of animal origin in food products. However, such proteins often present some limitations in their functional and nutritional properties. Therefore, the objectives of this study were to prepare a protein concentrate from noni seeds (NSPC) and to evaluate the impact of ultrasound (42 kHz, 130 W, 20 min and 40 min) on their structural, physicochemical, and functional properties. According to the results obtained, ultrasound modified the secondary and tertiary protein structures of NSPC, with changes that were reflected through the parameters of surface hydrophobicity, fluorescence intensity, molecular flexibility, particle size, as well as the contents of sulfhydryls, α-helix, β-sheet, β-turn and random coil. As a consequence of these modifications, the protein purity of NSPC increased by 7.5%, protein solubility by 90.90%, oil holding capacity by 12.0%, emulsifying capacity by 17.1%, emulsion stability by 15.12%, and foaming capacity by 25.7%. Furthermore, protein digestibility and antioxidant capacity were increased by 4.32% and 6.49%, respectively. Therefore, the modification of the physicochemical, functional, biochemical and structural properties of NSPC by the effect of ultrasound enhances its application as a food ingredient. Further research is needed to evaluate the performance of NSPC in specific foods.