Citrus Pectin

Abstract

Bibliography 16 PURPOSE OF INVESTIGATION Lemon, orange, and grapefruit residue, thousands of tons of which are discarded each year at citrus by-product factories, consists principally of peel, pulp, and seeds. From 1.5 to 3 per cent of such residue, depending upon the ripeness of the fruit, is pectin, which occurs largely as pectose, an insoluble material, in the covering of the intercellular walls of the peel. Pectin is a necessary constituent of jellies and marmalades. When 14730'-26t 1 2 BULLETIN 1323, U. S. DEPARTMENT OF AGRICULTURE RESULTS OF PREVIOUS INVESTIGATIONS Pectin was discovered in 1825 by Braconnot (6). Since then the chemistry of pectin and its related compounds has been the subject of extended research. Czapek (18), von Lippmann (36), Grafe (1), Beilstein (4), and Toll ens (50) have summarized these investigations. Bigelow, Gore, and Howard (5) give a review, with an extended bibliography, of the work done up to 1905. More recently Ehrlich (20), Oden (39), and Fellenberg (24) have published work on this subject. Confusion in designating substances of a pectinous nature has always existed. Fellenberg's exhaustive research helps to clarify the matter by giving the relations between the compounds. All pectinous materials are derived from pectose, or protopectin, an insoluble substance which forms the covering of the intercellular walls and middle lamella of unripe and some ripe, but no overripe, fruit.