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United States Department of Agriculture

Agricultural Research Service

Research Project: ENHANCED UTILIZATION OF CARBOHYDRATES AND POLYSACCHARIDES FROM CITRUS PROCESSING WASTE STREAMS

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Title: Contactless conductivity: an HPLC method to analyze degree of methylation of pectin

Authors
item Luzio, Gary
item Cameron, Randall

Submitted to: Proceedings of Florida State Horticultural Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 5, 2010
Publication Date: December 29, 2010
Citation: Luzio, G.A., Cameron, R. 2010. Contactless conductivity: an HPLC method to analyze degree of methylation of pectin. Proceedings of Florida State Horticultural Society. 123:213-216.

Interpretive Summary: Pectin, which is both a polyester and a polysaccharide, is a major component of citrus peel byproducts. In order to understand the functional properties of pectin being used to create new industrial materials from citrus waste it is important to verify its composition such as its ester content. The ester content of pectin has a significant on its functional properties. Measuring the ester content by traditional procedures is cumbersome and time consuming. We have devised a new approach for measuring the ester content which can be applied simultaneously to the measurement of molecular weight which is also and important attribute. This will be a valuable aid for new product development.

Technical Abstract: After removal of soluble sugars and other compounds by washing, citrus peel is largely composed of pectin, cellulose and hemicellulose. One of the major components, pectin can be modified using pectinesterases which reduces the degree of methylation (DM) to produce lower DM pectins which have great utility in the food industry and other applications. These lower DM pectins have been shown to have calcium sensitivity which is an important functional property of pectins for use in applications which require suspension, metal ion binding or water absorption. Thus the measurement of degree of methylation is an important attribute. Reduction in DM results in production of carboxyl groups which are ionic and conductive. Data shows that the conductivity as measured by CC4 conductivity meter increases with decreasing DM with values ranging from 94.0 to zero when pectins are analyzed on size exclusion chromatography columns (SEC) with concentration data measured with interferometric refractive index detector (RI). Best data fit is linear equation of y = -5.96 x 10-3 + 0.592 correlation coefficient of 0.998. Data demonstrates the DM can be measured simultaneously with molecular weight on SEC.

Last Modified: 10/22/2014
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