Propylene glycol alginate

• USP–NFPropylene Glycol Alginate

alginic acid propylene glycol ester; hydroxypropyl alginate; propane-1,2-diol alginate; Kelcoloid; Manucol Ester; E405

Propylene glycol ester of alginic acid (alginic acid partly esterified with propylene glycol; the remaining carboxyl groups free or neutralised) · [9005-37-2]

(C9H14O7)n (esterified unit)

Gelling agent, viscosity modifier

Typical concentrations: — · Dosage forms: Liquid

Used as a suspending agent, stabiliser, emulsifier, thickener and gelling agent in oral and topical preparations and, very widely, in foods such as salad dressings, sauces and beer (as a foam stabiliser). Its main advantage over sodium alginate is that it remains soluble and effective in acidic media. It is used at low concentrations, generally well below 1% w/w.

A white to yellowish, fibrous or granular powder that is practically odourless and tasteless. Grades differ in degree of esterification and in solution viscosity.

Solubility

soluble in water and in dilute organic acids, forming viscous colloidal solutions; practically insoluble in most organic solvents

Acid tolerance

remains in solution at low pH (down to about pH 3), where sodium alginate would precipitate as alginic acid

Viscosity

grade-dependent; low- to high-viscosity grades are available

The powder is stable when stored in a well-closed container in a cool, dry place. Aqueous solutions are most stable in mildly acidic conditions; in alkaline solution the ester groups are saponified and the material reverts to an alginate salt. Solutions are susceptible to microbial spoilage and may need a preservative.

Incompatible with alkalis, which hydrolyse the ester, and with strong oxidising agents. Because many carboxyl groups are esterified, it is less sensitive to calcium and other polyvalent cations than sodium alginate.

Alginic acid extracted from brown seaweeds is reacted with propylene oxide under controlled conditions so that part of the carboxyl groups are esterified; the remainder are left free or neutralised with an alkali. The product is then dried and milled.

Widely used in foods and regarded as non-toxic and non-irritant. It is poorly absorbed, and part of the propylene glycol may be released by hydrolysis in the gut. JECFA has allocated an acceptable daily intake of 0–70 mg/kg body weight.

Observe normal precautions for the quantity handled. Eye protection and gloves are recommended, and a dust mask where dust is generated.

Approved as a direct food additive in the USA and accepted in Europe as a food additive (E405).

Alginic acid; calcium alginate; potassium alginate; sodium alginate; propylene glycol.

Propylene glycol alginate is chosen over other alginates for acidic liquids and for systems that contain calcium. Its partial ester structure also gives it some surface activity, which contributes to its emulsifying and foam-stabilising action.