title: Characterization of citrus pectin samples extracted under different conditions: influence of acid type and pH of extraction.
abstract: OBJECTIVE
  Pectin is a complex macromolecule, the fine structure of which is influenced by many factors. It is used as a gelling, thickening and emulsifying agent in a wide range of applications, from food to pharmaceutical products. Current industrial pectin extraction processes are based on fruit peel, a waste product from the juicing industry, in which thousands of tons of citrus are processed worldwide every year. This study examines how pectin components vary in relation to the plant source (orange, lemon, lime, grapefruit) and considers the influence of extraction conditions on the chemical and macromolecular characteristics of pectin samples.
  
  
  METHODS
  Citrus peel (orange, lemon, lime and grapefruit) from a commercial supplier was used as raw material. Pectin samples were obtained on a bulk plant scale (kilograms; harsh nitric acid, mild nitric acid and harsh oxalic acid extraction) and on a laboratory scale (grams; mild oxalic acid extraction). Pectin composition (acidic and neutral sugars) and physicochemical properties (molar mass and intrinsic viscosity) were determined.
  
  
  RESULTS
  Oxalic acid extraction allowed the recovery of pectin samples of high molecular weight. Mild oxalic acid-extracted pectins were rich in long homogalacturonan stretches and contained rhamnogalacturonan I stretches with conserved side chains. Nitric acid-extracted pectins exhibited lower molecular weights and contained rhamnogalacturonan I stretches encompassing few and/or short side chains. Grapefruit pectin was found to have short side chains compared with orange, lime and lemon. Orange and grapefruit pectin samples were both particularly rich in rhamnogalacturonan I backbones.
  
  
  CONCLUSIONS
  Structural, and hence macromolecular, variations within the different citrus pectin samples were mainly related to their rhamnogalacturonan I contents and integrity, and, to a lesser extent, to the length of their homogalacturonan domains.
authors: INRA, UR1268 Biopolymères Interactions Assemblages, 44300 Nantes, France.
authors: Merve
authors: M
authors: Kaya
authors: CP Kelco ApS., Ved Banen 16, DK-4623 Lille Skensved, Denmark University of Copenhagen, Faculty of Science, Department of Plant and Environmental Sciences, DK-1871 Frederiksberg, Denmark.
authors: António G
authors: AG
authors: Sousa
authors: INRA, UR1268 Biopolymères Interactions Assemblages, 44300 Nantes, France.
authors: Marie-Jeanne
authors: MJ
authors: Crépeau
authors: CP Kelco ApS., Ved Banen 16, DK-4623 Lille Skensved, Denmark.
authors: Susanne O
authors: SO
authors: Sørensen
authors: INRA, UR1268 Biopolymères Interactions Assemblages, 44300 Nantes, France marie-christine.ralet@nantes.inra.fr.
authors: Marie-Christine
authors: MC
authors: Ralet
mesh_terms: D002241:Carbohydrates / Q000032:analysis / Q000302:isolation & purification; D002957:Citrus / Q000737:chemistry*; D005638:Fruit / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008970:Molecular Weight; D017942:Nitric Acid; D019815:Oxalic Acid; D010368:Pectins / Q000032:analysis / Q000302:isolation & purification*; D027821:Rutaceae / Q000737:chemistry*
chemical_list: D002241:Carbohydrates; C042491:rhamnogalacturonan I; C042492:rhamnogalacturonan II; D017942:Nitric Acid; D010368:Pectins; D019815:Oxalic Acid; C003181:polygalacturonic acid
keywords: Citrus peel; HG; Pectin; RGI; RGII; Rutaceae; grapefruit; homogalacturonan; industrial extraction; lemon; lime; orange; plant cell wall polysaccharide; rhamnogalacturonan