title: Storage related changes of cell wall based dietary fiber components of broccoli (Brassica oleracea var. italica) stems.
abstract: Storage related changes in the cell wall composition potentially affect the texture of plant-based foods and the physiological effects of cell wall based dietary fiber components. Therefore, a detailed characterization of cell wall polysaccharides and lignins from broccoli stems was performed. Freshly harvested broccoli and broccoli stored at 20°C and 1°C for different periods of time were analyzed. Effects on dietary fiber contents, polysaccharide composition, and on lignin contents/composition were much more pronounced during storage at 20°C than at 1°C. During storage, insoluble dietary fiber contents of broccoli stems increased up to 13%. Storage related polysaccharide modifications include an increase of the portions of cellulose, xylans, and homogalacturonans and a decrease of the neutral pectic side-chains arabinans and galactans. Broccoli stem lignins are generally rich in guaiacyl units. Lignins from freshly harvested broccoli stems contain slightly larger amounts of p-hydroxyphenyl units than syringyl units. Syringyl units are predominantly incorporated into the lignin polymers during storage, resulting in increased acetyl bromide soluble lignin contents. NMR-based analysis of the interunit linkage types of broccoli stem lignins revealed comparably large portions of resinol structures for a guaiacyl rich lignin. Incorporation of syringyl units into the polymers over storage predominantly occurs through β-O-4-linkages.
authors.affiliation: Department of Food Chemistry and Phytochemistry, Institute of Applied Biosciences, Karlsruhe Institute of Technology (KIT), Adenauerring 20A, 76131 Karlsruhe, Germany. Electronic address: judith.schaefer@kit.edu.
authors.forename: Judith
authors.initials: J
authors.lastname: Schäfer
authors.affiliation: Department of Food Chemistry and Phytochemistry, Institute of Applied Biosciences, Karlsruhe Institute of Technology (KIT), Adenauerring 20A, 76131 Karlsruhe, Germany. Electronic address: luisastanojlovic@googlemail.com.
authors.forename: Luisa
authors.initials: L
authors.lastname: Stanojlovic
authors.affiliation: Department of Safety and Quality of Fruit and Vegetables, Max Rubner-Institut (MRI), Haid-und-Neu-Straße 9, 76131 Karlsruhe, Germany. Electronic address: bernhard.trierweiler@mri.bund.de.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Trierweiler
authors.affiliation: Department of Food Chemistry and Phytochemistry, Institute of Applied Biosciences, Karlsruhe Institute of Technology (KIT), Adenauerring 20A, 76131 Karlsruhe, Germany. Electronic address: mirko.bunzel@kit.edu.
authors.forename: Mirko
authors.initials: M
authors.lastname: Bunzel
mesh_terms: D001937:Brassica / Q000737:chemistry* / Q000648:ultrastructure; D002236:Carbohydrate Conformation; D002473:Cell Wall / Q000737:chemistry; D004043:Dietary Fiber / Q000032:analysis*; D061353:Food Storage / Q000379:methods*; D008031:Lignin / Q000032:analysis / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D018547:Plant Stems / Q000737:chemistry / Q000648:ultrastructure; D011134:Polysaccharides / Q000032:analysis / Q000737:chemistry; D013997:Time Factors
chemical_list: D004043:Dietary Fiber; D011134:Polysaccharides; D008031:Lignin
keywords: Broccoli; Lignin; Non-starch polysaccharides; Pectin; Post-harvest modifications; Texture