Pectin extraction from common fig skin by different methods: The physicochemical, rheological, functional, and structural evaluations

Four extraction methods of hot-water (HWE), ultrasound-assisted (UAE), microwave-assisted (MAE), and ultrasound-microwave assisted (UMAE) were utilized to determine the best technique to extract pectin from the common fig (Ficus carica L) skin. UMAE (11.71%) significantly showed a more extraction yield than MAE (9.26%), UAE (8.74%), and HWE (6.05%). A significant dose-dependent antioxidant capacity for pectins 1,1-diphenyl-2-picryl-hydrazyl (DPPH), and 2,2'-azinobis (3-ethylbenzothiazoline-6-sulphonicacid) (ABTS) radical scavenging activity was found. The UMAE-pectin with the maximum galacturonic acid content (76.85%) and molecular weight (6.91 x 10(3) kDa) presented the highest emulsifying activity (612-61.3%) and emulsion stability (94.3-95.2%) with a monomodal droplet size distribution at cold and ambient storage temperatures. A non Newtonian shear-thinning behavior was detected at 1.5-3.0% pectic-solutions. X-ray diffraction (XRD) analysis showed a non-crystalline nature for pectins extracted by UMAE. FTIR spectroscopy and HPLC photodiode array detector revealed that conventional and novel extraction technologies do not change the chemical structure and monosaccharide composition of pectin significantly. (C) 2019 Elsevier B.V. All rights reserved.