The hydrophobic polysaccharides of apple pomace

Pedro A R Fernandes; Artur M S Silva; Dmitry V Evtuguin; Fernando M Nunes; Dulcineia F Wessel; Susana M Cardoso; Manuel A Coimbra

doi:10.1016/j.carbpol.2019.115132

The hydrophobic polysaccharides of apple pomace

Carbohydr Polym. 2019 Nov 1:223:115132. doi: 10.1016/j.carbpol.2019.115132. Epub 2019 Jul 26.

Authors

Pedro A R Fernandes¹, Artur M S Silva¹, Dmitry V Evtuguin², Fernando M Nunes³, Dulcineia F Wessel⁴, Susana M Cardoso¹, Manuel A Coimbra⁵

Affiliations

¹ QOPNA and LAQV-REQUIMTE, Department of Chemistry, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.
² CICECO, Department of Chemistry, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.
³ CQ-VR, Chemistry Research Centre, Department of Chemistry, Universidade de Trás-os-Montes e Alto Douro, 5000-801 Vila Real, Portugal.
⁴ QOPNA and LAQV-REQUIMTE, Department of Chemistry, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal; School of Agriculture and CI&DETS, Polytechnic Institute of Viseu, 3500-606 Viseu, Portugal; CITAB - Centre for the Research and Technology of Agro-Environmental and Biological Sciences, Universidade de Trás-os-Montes e Alto Douro, 5000-801 Vila Real, Portugal.
⁵ QOPNA and LAQV-REQUIMTE, Department of Chemistry, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal. Electronic address: mac@ua.pt.

PMID: 31426977
DOI: 10.1016/j.carbpol.2019.115132

Abstract

In this work, polysaccharides extracted with hot water from apple pomace were isolated by C18 cartridge solid-phase extraction at pH 7 (Fr7). Dialysis (12-14 kDa) of this fraction allowed to obtain 17% (w/w) of polymeric material composed by 65% of polysaccharides, mainly arabinose (58 mol%), galacturonic acid (16 mol%) and glucose (10 mol%). Folin-Ciocalteu assay showed 62 g of phloridzin equiv/kg of polyphenols. Moreover, adjusting to pH 3, it was possible to retain an additional fraction (Fr3) representing a further 4% of the polymeric material. Fr3 contained 53% of polysaccharides composed mainly by galacturonic acid (66 mol%) and polyphenols accounted for 37 g of phloridzin equiv/kg. Precipitation with ethanol and subsequent methylation and NMR spectroscopic analysis of Fr7 dialysate allowed the identification of covalently-linked pectic-polyphenol-xyloglucan and arabinan-polyphenol complexes. These structures are possibly formed as a result of polyphenol oxidation reactions during the industrial processing of apples, conferring hydrophobic characteristics to apple pomace polysaccharides.

Keywords: Arabinan; NMR; Pectic polysaccharides; Polyphenol interaction; Xyloglucan.