De-esterification of pectin by alkali, plant and fungal pectinmethylesterases and effect on molecular weight

Commercial high methoxyl pectin was de-esterified using chemical saponification or by pectinmethylesterases. A commercial fungal pectin methyl esterase (PME) (EC 3.1.1.11), free of polygalacturonase, or a citrus Valencia PME was used to de-esterify pectin enzymatically to a targeted degree of esterification. The apparent molecular weight of pectin did not change by extended times of Valencia PME treatment and ranged from 154100 to 183500. Fungal PME-modified pectins had moderately increased apparent molecular weight that ranged from 123900 to 169800. The increase in molecular weight was attributed to aggregation. The molecular weight of pectins that were de-esterified by alkali decreased from about 156200 to 91200. Citrus Valencia or fungal PME modification alters the charge of pectin without loss of high molecular weight.