Caprylic acid

Description and assay

Specification history

Prepared at the 82 nd JECFA (2016), published in FAO JECFA Monograph 19 (2016), superseding specifications prepared at the 63 rd JECFA (2004) and published in FNP 52 Add 12 (2004). Small residues of octanoic acid on food (which has been treated with antimicrobial washing solutions) at the time of consumption would not pose a safety concern (63 rd JECFA, 2004).

Chemical name

Octanoic acid

C.A.S. number

124-07-2

Chemical formula

CH 3 (CH 2 ) 6 CO 2 H

Formula weight

144.21

Assay

Not less than 95%

DESCRIPTION

Colourless oily liquid

FUNCTIONAL USES

Antifoaming agent, surfactant, flavouring agent (see JECFA No. 99)

METHOD OF ASSAY

Determine using an appropriate gas chromatographic technique. The selection of sample size and method of sample preparation may be based on AOCS Method Ce 1-62 and Ce 1j-07 and follow the principles of the method described in Vol. 4 (under Analytical Techniques, Gas Chromatography). The percentage of octanoic acid is the area percent of the methyl octanoate peak. Decanoic acid may be determined using the same gas chromatographic technique.

Identification

Solubility (Vol. 4)

Slightly soluble in water; soluble in most organic solvents

frared spectrum (Vol. 4)

The infrared spectrum of a liquid film of a sample corresponds to the reference infrared spectrum in the Annex. Hold 1 to 2 drops of a sample between two optical plates and examine the liquid film of a sample between the plates using an infrared spectrometer. The optical plates are usually made by sodium chloride or potassium bromide.

Acid value (Vol. 4)

Between 366 and 396

Purity criteria

Water (Vol. 4)

Not more than 0.4% (Karl Fischer Method)

Sulfated ash (Vol. 4)

Not more than 0.1% Test 10 g of the sample (Method II)

Unsaponifiable matter

Not more than 0.2% See description under TESTS

Iodine value (Vol. 4)

Not more than 2.0

Decanoic acid

Not more than 3% See description under METHOD OF ASSAY

Lead (Vol. 4)

Not more than 2 mg/kg Determine using a method appropriate to the specified level. The selection of sample size and method of sample preparation may be based on the principles of the method described in Volume 4 (under “General Methods, Metallic Impurities”).

Test: Unsaponifiable matter

Weigh accurately 5.0 g of the sample into a 250 ml flask, add a solution of 2 g of potassium hydroxide in 40 ml of ethanol, and boil gently under a reflux condenser for 1 h or until saponification is complete. Transfer the contents of the flask to a glass-stoppered graduated extraction cylinder. Wash the flask with sufficient ethanol to make a volume of 40 ml in the cylinder, and complete the transfer with warm and then cold water until the total volume is 80 ml. Finally, wash the flask with a few ml of petroleum ether, add the washings to the cylinder, cool the contents of the cylinder to room temperature, and add 50 ml of petroleum ether. Insert the stopper, shake the cylinder vigorously for at least 1 min, and allow both layers to become clear. Siphon the upper layer as completely as possible without removing any of the lower layer, collecting the ether fraction in a 500-ml separator. Repeat the extraction and siphoning at least six times with 50-ml portions of petroleum ether, shaking vigorously each time. Wash the combined extracts, with vigorous shaking, with 25-ml portions of 10% ethanol until the wash water is neutral to phenolphthalein, and discard the washings. Transfer the petroleum ether extract to a tared beaker, and rinse the separator with 10 ml of petroleum ether, adding the rinsings to the beaker. Evaporate the solvent on a steam bath just to dryness, and dry the residue to constant weight, preferably at 75  to 80  under a vacuum of not more than 200 mm of Hg, or at 100  for 30 min. Cool in a desiccator, and weigh to obtain the uncorrected weight of unsaponifiable matter. Determine the quantity of fatty acids in the residue as follows: Dissolve the residue in 50 ml of warm ethanol (containing phenolphthalein TS and previously neutralized with sodium hydroxide to a faint pink colour), and titrate with 0.02 M sodium hydroxide to the same color. Each ml of 0.02 M sodium hydroxide is equivalent to 5.659 mg of fatty acids, calculated as oleic acid. Subtract the calculated weight of fatty acids from the weight of the residue to obtain the corrected weight of unsaponifiable matter in the sample.

Test: Appendix

Infrared spectrum of octanoic acid standard