Pectins
Molecular structure
The pectin molecule is basically a chain of galacturonic acid units. The regular structure is interrupted by the presence of a methylpentose, L-rhamnose, which causes deviations called "pectic elbows". The L-rhamnose is linked by carbons 1 and 2.
GALACTURONIC ACID INTERRUPTED BY RHAMNOSE
A certain proportion of these galacturonic acids are in the methyl ester form. The percentage of the galacturonic acids that are esterified is called the degree of esterification (DE) or degree of methoxylation (DM).
High methoxyl (HM) pectins are defined as those with a DE above 50, while low methoxyl (LM) pectins have a DE of less than 50. LM pectins can be acid or alkali-treated. LM pectins can be either amidated (LMA) or non-amidated (LM).