Extraction, Characterization And Polysaccharide Composition Of Pectin From Pineapple [Ananas Comosus (L) Merr] Rind

The composition and properties of pectin from monocotyledon have not been studied extensively as pectins investigated currently are normally extracted from dicotyledonous plants, including citrus, orange, apple, sunflower, sugar beet and potato. Pineapple (Ananas comosus (L) Merr) is a common monocotyledonous plant grown in south China, whose fruit can be consumed fresh, canned or juiced. Only40%of pineapple is edible whereas the rind is usually thrown away or used for animal feeding. It has been reported to be potential source of pectin. However, reported investigation on pineapple pectin is limited.This study investigated the acid-extracted pectin from pineapple rind for the best conditions, and improved the extraction and alcohol-precipitation conditions. The structure and composition of pineapple rind pectin was analyzed, and compared with the common pectins from dicotyledonous plants (apple, citrus).Fresh pineapple rind was treated in three ways to deactivate enzymes:It was found that enzyme deactivation significantly increased the pectin yield, especially the blenching way. By considering pectin yield and GalA content, the pineapple rind pectin was extracted at80℃, pH2.0for100min with solid-liquid ratio1:15, and precipitated with ethanol in the ratio1:2.5(v/v) at pH3.7. could be suitable. The yield and GalA content of pineapple rind pectin was4.68%and68.73%48.73%, respectively.Pineapple rind pectin consisted of acetyl groups and six monosaccharides, with a DE value of48.73%. Its monosaccharides constituents differed from pectins from dicotyledonous plants for the presence of mannose and high content of arabinose.Pineapple rind pectin was completely fractionated into one neutral fraction (PRP-N) and two acidic fractions (PRP-1and PRP-2) by ion-exchange chromatography. PRP-1was characterized by high amounts of rhamnose, galactose and arabinose, indicating that rhamnogalacturonan type I with longer arabinose-and galactose-rich side chains were part of this fraction. Also the GalA-rich PRP-2 contained homogalacturonan as well as rhamnogalacturonan type Ⅱ with a very low neutral sugar content. PRP-2showed one broad hydrodynamic volume distribution, representing its diversity in particle size in solution.