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United States Department of Agriculture

Agricultural Research Service

Title: Mapping Demethylated Block Size and Distribution in Pectin from Citrus Processing Waste

item Cameron, Randall
item Grohmann, Karel - RETIRED USDA

Submitted to: Subtropical Technology Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: October 15, 2004
Publication Date: October 21, 2004
Citation: Cameron, R.G., Grohmann, K. 2004. Mapping demethylated block size and distribution in pectin from citrus processing waste. Subtropical Technology Conference Proceedings. 55:43.

Technical Abstract: The functional properties of pectin are dependent on structural features of the individual pectin molecules in a solution. The primary structural components responsible for pectin functionality are the proportion of galacturonic acid (GA) residues in the homogalacturonan (HGA) region that are methyl esterified, the distribution of the esterified GA residues within the HGA (block vs. random) and the average molecular weight of the pectin molecules that make up the population. We are using a mono-component thermally-tolerant pectin methylesterase (TT-PME) to demethylate pectin and determine its structural affect on demethylated and methyl-protected block size. We investigated the utility of an evaporative light scattering detector (ELSD) coupled to High Performance Size Exclusion and Anion Exchange Chromatography systems to detect and quantify galacturonic acid oligomers released from demethylated pectin by digestion with endo-polygalacturonase and subsequent saponification with lithium hydroxide. Construction of calibration curves demonstrates that the ELSD can detect larger GA oligomers than previously detected and can be used to quantify the amount of individual GA oligomers. Results also indicate that the TT-PME mode of action apparently changes from a single chain mechanism to a multiple attack mechanism dependent on pH of the reaction.

Last Modified: 4/17/2015
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