Development of sustainable approaches based on ultrasound-assisted extraction and pressurized liquid extraction to obtain proteins and bioactive peptides from grapefruit peels.

This study presents the development of several approaches to obtain, for the first time, proteins and bioactive peptides from grapefruit peels. The experimental conditions of three extraction methodologies based on the use of Ultrasound-Assisted Extraction (UAE) with Tris-HCl buffer, UAE with Natural Deep Eutectic Solvents, and Pressurized Liquid Extraction (PLE) were optimized. Among them, PLE proved to be the most effective approach, yielding a protein-rich extract containing 70% protein. Protein extracts obtained by PLE were submitted to enzymatic hydrolysis with Thermolysin, Alcalase, and Alcalase Pure, and the resulting protein hydrolysates were then evaluated for their antioxidant and antihypertensive activities. Finally, peptides and other molecules present in the protein hydrolysates were identified using ultra-high liquid chromatography coupled to hybrid quadrupole-Orbitrap mass spectrometry. Thus, a total of 75 peptides along with 31 additional compounds mainly classified into the families of flavonoids, carboxylic acids, amino acids, and carbohydrates were identified.