Sustainable Extraction of Pectin from Peach Fruit Using Natural Deep Eutectic Solvents (NADESs)

Pectin is a widely used biopolymer in the food, pharmaceutical, and environmental industries. Traditionally extracted from citrus and apple peels using harsh acids and high energy inputs, conventional methods raise environmental and sustainability concerns. Recent research has turned toward greener extraction technologies, including the use of Natural Deep Eutectic Solvents (NADESs) as environmentally friendly alternatives to conventional solvents. In this study, pectin was extracted from peach fruit using six different NADES formulations. Each solvent was prepared with choline chloride (ChCl) as a hydrogen bond acceptor (HBA) and one of six organic acids, lactic acid (LA), acetic acid (AA), malic acid (MA), malonic acid (MalA), oxalic acid (OA), or citric acid (CA), as the hydrogen bond donor (HBD), in a 1:1 (w/w) molar ratio. Extractions were performed at 80 °C for 2 hours with ultrasonic assistance, and the NADES solutions were diluted with 3.5% ultrapure water. Yields were compared to those from conventional solvents (0.2 N citric acid and HCl, pH 1.5). The highest pectin yield (5.27 ± 0.08%) was obtained using ChCl:LA. The extracted pectins were characterized via Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). FTIR analysis revealed the highest degree of esterification (DE) in pectin extracted with ChCl:CA (52.92%). Pectins were classified as high methoxyl (HM, DE > 50%) or low methoxyl (LM, DE < 50%). Conventional methods produced HM pectins with DE values of 51.35% (HCl) and 53.46% (citric acid). Among NADES extractions, ChCl:AA (50.6%), ChCl:CA (52.92%), and ChCl:MA (55.77%) also yielded HM pectins, while ChCl:LA (34.19%), ChCl:MalA (45.65%), and ChCl:OA (16.81%) resulted in LM pectins. In conclusion, ChCl:LA was the most effective solvent for maximizing pectin yield from peach fruit, while ChCl:MA was optimal for producing high methoxyl pectin. These findings support the potential of NADES as a green, sustainable approach for biopolymer extraction from fruit matrices.