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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

Authors
item Cameron, Randall
item Grohmann, Karel - RETIRED, USDA

Submitted to: Annual Meeting of the Institute of Food Technologists
Publication Type: Abstract Only
Publication Acceptance Date: July 9, 2004
Publication Date: July 16, 2004
Citation: Cameron, R.G., Grohmann, K. 2004. Mapping demethylated block size and distribution in pectin from citrus processing waste. Annual Meeting of the Institute of Food Technologists. Book of Abstracts. p. 147. Paper No. 56-5.

Technical Abstract: The citrus processing waste stream is composed mainly of the fruit peel and any rag tissue (segment membranes, core tissue) remaining after juice extraction. Current practice is to convert this waste material to citrus peel pellets (CPP) which are marketed as a low priced animal feed. For the 2002-2003 season over 750,000 tons of dried CPP were shipped at a price of only 3 - 4 cents per pound. The major component of citrus peel that possesses functionality and value is pectin. Functional properties of citrus pectin are primarily dependent on molecular weight (a function of the degree of polymerization of galacturonic acid residues) and the proportion of the galacturonic acid (GA) carboxyl groups that are methyl esterified (degree of esterification). More recently it has been demonstrated that the distribution of methyl esters (random vs. ordered) along the homogalacturonan chain also affect functionality. Functionality also may be influenced by block size (number of contiguous de-esterified GA residues) and their distribution along the homogalacturonan chain. Functional properties that are, or may be, affected by methyl ester distribution are rheology, calcium sensitivity, cation exchange capacity, gel elasticity, response to compressive strain, gel pore size and structure and water holding capacity. In order to understand the relationship between methyl ester distribution and functionality it is necessary to determine the size distribution of esterified and de-esterfied blocks, the frequency of each size class and how changing these variables affects functionality.

Last Modified: 8/22/2014
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