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United States Department of Agriculture

Agricultural Research Service

Title: Determination of Galacturonic Acid Content of Pectin Using a Microtiter Plate Assay

item Luzio, Gary

Submitted to: Proceedings of Florida State Horticultural Society
Publication Type: Abstract Only
Publication Acceptance Date: February 28, 2004
Publication Date: N/A

Technical Abstract: The amount of galacturonic acid residues in samples containing pectin is an important parameter in the quantitative and structural analysis of these complex carbohydrates. This paper describes a method to determine the content of galacturonic acids in samples containing pectin, using a glass microtiter plate and microtiter plate-reading equipment with standard interference filters. The assay is a modification of a commonly used procedure involving the hydrolysis of pectin in 80% sulfuric acid at 80°C followed by a coloring step with 3,5-dimethylphenol reagent at room temperature. The previous assay was difficult to apply routinely if large numbers of samples must be analyzed due to color changes that are time dependent and transferring of strongly acidic solutions to a cuvette prior to reading. The use of microtiter plate assay has several practical advantages such as an accurate estimate of background absorbance by multiple reading of the plates and the fact that many samples can be rapidly assayed in one plate to minimize errors due to fading of the final color. This method is particularly advantageous when a large number of pectin samples must be analyzed for their content of galacturonic acid residues.

Last Modified: 4/19/2015
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