pectin

Pectin
Source: Cell walls of higher plants (citrus rind)
Structure: Largely a linear polymer of polygalacturonic acid with varying degrees of methyl esterification. 
>50% esterified is a high methoxy (HM) pectin
<50% esterified is a low methoxy (LM) pectin
Functional Properties:
High methoxy pectin will gel in the presence of acid and high sugar concentrations.   Low methoxy pectin will gel in the presence of calcium.
Pectin is a naturally occurring biopolymer that is finding
increasing applications in the pharmaceutical and biotechnology
industry. It has been used successfully for many years in the food
and beverage industry as a thickening agent, a gelling agent and a
colloidal stabiliser.
 
Most commercial pectins come from apple or waste from manufacture of apple products (10-15% pectins), citrus wastes (20-30% pectins) and from sugar beet processing.
Pectins are extracted by heating the plant materials in water (60-95 C) and at an acidic pH (2.5).
The pectins are precipitated with ethanol and removed by centrifugation.
As is true for gums, humans are incapable of digesting pectins.
However, bacteria in our gut ca