Physicochemical and functional characteristics of a gourd (Cucurbita argyrosperma Huber) seed protein isolate subjected to high-intensity ultrasound

• Published in: Heliyon Vol. 10; no. 11; p. e32225
• Main Authors: Carrillo, Yessica Silva, Ulloa, José Armando, Urías Silvas, Judith Esmeralda, Ramírez Ramírez, José Carmen, Leyva, Ranferi Gutiérrez
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 15-06-2024; Elsevier
• Subjects: Functional properties; Gourd; Physicochemical properties; Power ultrasound; Structural properties; Functional properties; Gourd; Physicochemical properties; Structural properties; Power ultrasound
• ISSN: 2405-8440; 2405-8440
• DOI: 10.1016/j.heliyon.2024.e32225

The impact of high-intensity ultrasound (HIU, 20 kHz) on the physicochemical and functional characteristics of gourd seed protein isolate (GoSPI) was studied. GoSPI was prepared from oil-free gourd seed flour through alkaline extraction (pH 11) and subsequent isoelectric precipitation (pH 4). The crude protein concentration of GoSPI ranged from 91.56 ± 0.17 % to 95.43 ± 0.18 %. Aqueous suspensions of GoSPI (1:3.5 w/v) were ultrasonicated at powers of 200, 400, and 600 W for 15 and 30 min. Glutelins (76.18 ± 0.15 %) were the major protein fraction in GoSPI. HIU decreased the moisture, ash, ether extract, and nitrogen-free extract contents and the hue angle, available water and a* and b* color parameters of the GoSPI in some treatments. The L* color parameter increased (7.70 %) after ultrasonication. HIU reduced the bulk density (52.63 %) and particle diameter (39.45 %), as confirmed by scanning electron microscopy, indicating that ultrasonication dissociated macromolecular aggregates in GoSPI. These structural changes enhanced the oil retention capacity and foam stability by up to 62.60 and 6.84 %, respectively, while the increases in the solvability, water retention capacity, and emulsifying activity index of GoSPI were 90.10, 19.80, and 43.34 %, respectively. The gelation, foaming capacity, and stability index of the emulsion showed no improvement due to HIU. HIU altered the secondary structure of GoSPI by decreasing the content of α-helices (49.66 %) and increasing the content of β-sheets (52.00 %) and β-turns (65.00 %). The electrophoretic profile of the GoSPI was not changed by HIU. The ultrasonicated GoSPI had greater functional attributes than those of the control GoSPI and could therefore be used as a functional food component.
[Display omitted]
•HIU altered the surface morphology and secondary structure of GoSPI.•The physicochemical and functional characteristics of GoSPI were modified by HIU.•HIU enhanced the protein concentration and color of GoSPI.•The oil retention capacity and foam stability of GoSPI increased due to HIU.•HIU decreased the bulk density and particle diameter of GoSPI.