Malic acid

• BPMalic Acid
• Ph. Eur.Malic Acid
• USP–NFMalic Acid

DL-Malic acid; hydroxybutanedioic acid; hydroxysuccinic acid; apple acid; acidum malicum; E296

(RS)-Hydroxybutanedioic acid · [6915-15-7]

UNII 817L1N4CKP · PubChem CID 525

C4H6O5 · 134.09

pH adjuster, buffering agent, Flavouring agent

Typical concentrations: — · Dosage forms: Liquid, Solid

Used as an acidulant, flavour enhancer and pH adjuster in oral liquids and chewable or effervescent products, where it gives a smooth, persistent sour taste and helps mask bitterness; it can replace citric acid in effervescent couples. It also acts as a mild chelating agent and antioxidant synergist, and is used in topical and cosmetic products.

White or almost white crystalline powder or granules with a slight odour and a strongly acidic taste. The pharmacopoeial material is the racemate; L-malic acid occurs naturally in fruits.

Melting point

about 128–132 °C (DL-form)

pKa

≈ 3.4 and ≈ 5.1 (25 °C)

Solubility

very soluble in water; freely soluble in ethanol (95%)

Density

≈ 1.6 g/cm³

Stable up to about 150 °C; at higher temperatures it slowly loses water, forming fumaric and maleic acids. It is less hygroscopic than citric acid. Store in a well-closed container in a cool, dry place.

Incompatible with strong oxidising agents and bases; reacts with carbonates and bicarbonates (the basis of effervescence). It can corrode some metals in the presence of moisture.

The racemate is made synthetically by hydration of maleic or fumaric acid at high temperature and pressure; L-malic acid can be produced by enzymatic hydration of fumaric acid.

A normal metabolite (in the citric acid cycle) and regarded as non-toxic at excipient levels; the concentrated acid is irritant to eyes and skin. Use of the DL-form in foods for infants is not recommended because of uncertainty about metabolism of the D-isomer.

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 (E296). Included in the FDA Inactive Ingredient Database (oral preparations) and in non-parenteral medicines licensed in Europe.

Citric acid; fumaric acid; maleic acid; tartaric acid; succinic acid.

Its sourness develops more gradually and lasts longer than that of citric acid, so it is often blended with citric acid to shape the taste profile of flavoured products.