Pectin

• USP–NFPectin

Pectinic acid; citrus pectin; apple pectin; high-methoxyl pectin; low-methoxyl pectin; amidated pectin; Genu; E440

Partially methyl-esterified poly(α-(1→4)-D-galacturonic acid), a plant polysaccharide · [9000-69-5]

(C6H10O7)n (galacturonic acid units, partly as methyl esters) · ≈ 30 000–100 000

Gelling agent, viscosity modifier

Typical concentrations: — · Dosage forms: Liquid

Used as a gelling, thickening, suspending and stabilising agent in oral liquids and foods, as an adsorbent in antidiarrhoeal mixtures (traditionally with kaolin), in mucoadhesive and colon-targeted drug delivery systems, and in a nasal spray in which it gels on contact with calcium in the nasal mucosa. It is also used in wound-care hydrocolloid dressings.

A white to yellowish or light brown, coarse or fine powder, practically odourless, with a mucilaginous taste. It is obtained from citrus peel or apple pomace.

Degree of esterification

high-methoxyl grades above 50%; low-methoxyl grades below 50%

Composition (USP)

methoxy groups not less than 6.7% and galacturonic acid not less than 74.0% (dried basis)

Solubility

soluble in water, forming a viscous, opalescent colloidal solution; practically insoluble in ethanol and other organic solvents

Gelation

high-methoxyl pectin gels with sugar at acidic pH (about 2.8–3.5); low-methoxyl pectin gels with calcium ions

pH

aqueous solutions are acidic

The dry powder is stable when kept cool and dry. In solution pectin is most stable at about pH 3–4; at neutral to alkaline pH and on heating it depolymerises (β-elimination) and de-esterifies, losing viscosity. Solutions support microbial growth. Store in an airtight container in a cool, dry place.

Incompatible with strong oxidising agents. Polyvalent cations (especially calcium) cause gelation or precipitation of low-methoxyl pectin, and as an anionic polymer it can interact with cationic drugs, surfactants and preservatives. Alcohol and high electrolyte concentrations precipitate it.

Extracted from citrus peel or apple pomace with hot dilute acid, then precipitated with alcohol, washed, dried and milled; low-methoxyl and amidated grades are made by controlled de-esterification with acid, alkali or ammonia.

Non-toxic and non-irritant. It is not digested in the small intestine but is fermented by colonic bacteria; large amounts may cause flatulence. JECFA has allocated an ADI 'not specified'.

Observe normal precautions for the quantity handled. Avoid generating dust; eye protection, gloves and a dust mask are recommended.

GRAS listed. Accepted as a food additive in Europe (E440). Used in licensed oral and nasal medicinal products.

Alginic acid; sodium alginate; carrageenan; gellan gum; xanthan gum.

Pectin powder tends to form lumps; disperse it with sugar or another dry ingredient, or in a little ethanol or glycerin, before adding water with stirring. The degree of esterification and amidation determines the gelling mechanism and must be matched to the formulation.