ARS | Publication request: EFFECT OF PH ON DE-ESTERIFIED AND METHYL-PROTECTED BLOCK SIZE IN PECTIN TREATED WITH THE SALT-INDEPENDENT PECTIN METHYLESTERASE FROM CITRUS FRUIT

Submitted to: Pacifichem Symposium
Publication Type: Abstract Only
Publication Acceptance Date: November 10, 2005
Publication Date: January 1, 2006
Citation: Cameron, R.G., Luzio, G.A. 2006. Effect of pH on de-esterified and methyl-protected block size in pectin treated with the salt-independent pectin methylesterase from citrus fruit. Pacifichem Symposium. Paper No. 22.

Technical Abstract: Degree of esterification (DE) is a primary determinate of the functional properties of commercial pectin. More recently it has been demonstrated that pectin rheology is dependent on the method of deesterification (ordered vs. random) as well as the overall DE. Previously we have shown that non-calcium sensitive pectin (DE = 73%) can be converted to calcium sensitive pectin with a minimal (6%) decrease in DE. Calcium sensitive pectins show a characteristic increase in solution viscosity in the presence of calcium ion whereas non-calcium sensitive pectins are not affected by calcium ion. The structures of these pectins have not been characterized. More recently we have developed a methodology enabling us to detect and quantify galacturonic acid oligomers up to a degree of polymerization of 70 and thereby determine structure. We have used this technology to study deesterification patterns produced by the thermally-tolerant pectin methylesterase (PME) and the mode of action of endo-polygalacturonases on oligomers with a DP greater than 8. In this work we will be presenting results of the above studies and structural (demethylated and methyl-protected block size) data resulting from the stepwise decrease in DE of non-calcium sensitive pectin after demethylation at pH 4.5 and 7.5 with the salt-independent PME from citrus fruit peel.