nonmethylesterified

Nonmethylesterified refers to a chemical state where a substance, typically a pectin or a similar polysaccharide, has not undergone methylation or has had its methyl groups removed. Pectins are complex carbohydrates found in the cell walls of plants. They are composed of galacturonic acid units, and the presence and degree of methylation of these units significantly influence their properties.

Methylation involves the attachment of methyl groups (CH3) to the carboxyl groups of the galacturonic acid units. This process is common in the commercial production of pectin, as it affects solubility, gelling ability, and interactions with other molecules. Pectins are broadly classified into high-methoxyl (HM) pectins and low-methoxyl (LM) pectins, based on their degree of esterification.

A nonmethylesterified pectin, therefore, would represent a state where these methyl groups are either absent from the outset or have been chemically removed, a process known as de-esterification. In a de-esterified state, the carboxyl groups are predominantly in their free acid form. This change in chemical structure alters the pectin's behavior, particularly its interaction with divalent cations like calcium ions. Nonmethylesterified pectins are often more reactive with calcium, leading to gel formation through ionic cross-linking, which is a key characteristic of LM pectins. The term is used to describe the absence of these specific chemical modifications.