Submitted to: Proceedings of Florida State Horticultural Society
Publication Type: Abstract Only
Publication Acceptance Date: April 20, 2003
Publication Date: N/A
Technical Abstract: A major component of the citrus juice processing waste stream is fruit peel. Every ton of waste peel contains 300 - 400 pounds of pectin (15 - 20 % on a wet weight basis), a complex polysaccharide in which galacturonic acid (GA) is the major constituent, comprising 80 - 90% of the pectin dry weight. The majority of the GA residues are located in linear homogalacturonan regions in which a variable proportion may be methylated at the C6 position. The functional properties of pectin are largely dependent on the fraction of GA residues that are methylated and their distribution along the homogalacturonan stretches. In order to map pectin fine structure and determine the size and distribution of methylated and demethylated GAs it is necessary to separate, detect and quantify oligogalacturonic acid fragments. We have developed chromatographic methods to accomplish these tasks. Data will be presented on the separation, identification and quantification of oligogalacturonides produced by either enzymatic or chemical hydrolysis. Results from ion exchange and size exclusion chromatography (SEC) will be included. The development of methods compatible with an evaporative light scattering detector (ELSD) have enabled us to accurately estimate masses associated with peak areas. Incorporating a post-column addition of potassium carbonate to a near neutral anion exchange buffer system has allowed us to use integrated amperometry to detect oligogalacturonides ranging in size from one to greater than 10 GA residues. Results from SEC coupled to either an ELSD or refractive index detector also will be presented.