title: Solid-state 13C NMR study of the mobility of polysaccharides in the cell walls of two apple cultivars of different firmness.
abstract: Solid-state (13)C nuclear magnetic resonance (NMR) was used to compare differences in mobility of the cell wall polysaccharides of 'Scifresh' and 'Royal Gala' apples after 20 weeks of storage. The texture of 'Scifresh' apples was markedly firmer than that of 'Royal Gala' at the end of storage. In a novel approach Two Pulse Phase Modulation (TPPM) decoupling was combined with cross polarisation (CP) and single pulse excitation (SPE) experiments. The resulting high resolution solid-state SPE spectra, unprecedented for apple cell walls, allowed a detailed insight into the physical and chemical properties of very mobile polysaccharides such as the arabinan and galactan side chains of the pectic polysaccharide rhamnogalacturonan I (RG-I). NMR showed that the cellulose rigidity was the same in the two cultivars, while arabinans were more mobile than galactans in both. Unexpectedly, arabinans in 'Scifresh' cell walls were more mobile than those in 'Royal Gala' which was unforeseen considering the greater firmness of the 'Scifresh' cultivar.
authors.affiliation: School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand; The New Zealand Institute for Plant and Food Research Limited, Private Bag 92169, Auckland 1142, New Zealand.
authors.forename: Jovyn K T
authors.initials: JK
authors.lastname: Ng
authors.affiliation: School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand; MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington, Wellington 6140, New Zealand; Centre for NMR, School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand. Electronic address: z.zujovic@auckland.ac.nz.
authors.forename: Zoran D
authors.initials: ZD
authors.lastname: Zujovic
authors.affiliation: School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
authors.forename: Bronwen G
authors.initials: BG
authors.lastname: Smith
authors.affiliation: The New Zealand Institute for Plant and Food Research Limited, Private Bag 1401, Havelock North 4157, New Zealand.
authors.forename: Jason W
authors.initials: JW
authors.lastname: Johnston
authors.affiliation: The New Zealand Institute for Plant and Food Research Limited, Private Bag 92169, Auckland 1142, New Zealand.
authors.forename: Roswitha
authors.initials: R
authors.lastname: Schröder
authors.affiliation: School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
authors.forename: Laurence D
authors.initials: LD
authors.lastname: Melton
mesh_terms: D002236:Carbohydrate Conformation; D002473:Cell Wall / Q000737:chemistry / Q000378:metabolism*; D061353:Food Storage; D005638:Fruit / Q000166:cytology*; D006244:Hardness; D009682:Magnetic Resonance Spectroscopy; D027845:Malus / Q000166:cytology*; D011134:Polysaccharides / Q000737:chemistry / Q000378:metabolism*
chemical_list: D011134:Polysaccharides
keywords: Fruit texture; Nuclear magnetic resonance; Pectin; Plant cell walls; Polysaccharide mobility; Two Pulse Phase Modulation decoupling