ARS | Publication request: INVESTIGATION OF GALACTURONIC ACID COLORIMETRIC ASSAY OF PECTIN IN CITRUS PEEL

Submitted to: Subtropical Technology Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: October 15, 2004
Publication Date: October 21, 2004
Citation: Luzio, G.A. 2004. Investigation of galacturonic acid colorimetric assay of pectin in citrus peel. Subtropical Technology Conference Proceedings. 55:42.

Technical Abstract: The amount of galacturonic acid residues in samples containing pectin is an important parameter in the quantitative and structural analysis of this complex carbohydrate. This presentation describes a method to determine the content of galacturonic acid in samples containing pectin such as citrus peel, using a glass microtiter plate and microtiter plate-reading equipment with standard interference filters. The assay is a modification of a 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 that involve 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 many samples can be rapidly assayed in one plate to minimize errors due to fading of the chromophore. This method is particularly advantageous when a large number of pectin samples must be analyzed for their content of galacturonic acid residues and is applicable to standard AOAC assays for pectin in fruits and vegetables.