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Other name  Theobroma Oil; Cacao Butter

Category  Pharmaceutic aid.

Definition  Cocoa butter is the solid fat obtained from the crushed and roasted seeds of Theobroma cacao L. (Family Sterculiaceae)

Origin of plant  Cocoa butter-yielding plant is native to Mexico, Central America and northern South America (Colombia, Ecuador, Venezuela, Brazil, Guyana, Surinam and French Guiana).

Constituents  Cacao Butter contains saturated fatty acids (stearic acid, palmitic acid, arachidic acid, myristic acid, and lauric acid), unsaturated fatty acids (oleic acid, linoleic acid, palmitoleic acid, etc.), and triglycerols.

Description  Yellowish white fat, becoming white on keeping; odour, faint and agreeable; taste, bland and chocolate-like if obtained by pressing or bland if obtained by extraction; usually brittle when cold, becoming soft at 25º.

Solubility  Freely soluble in boiling anhydrous ethanol and in light petroleum, slightly soluble in ethanol.

Packaging and storage Cocoa butter shall be kept in tightly closed containers, protected from light, and stored at a temperature not exceeding 25º.

Relative density About 0.895, at 40º (Appendix 4.9).

Refractive index About 1.457, at 40º  (Appendix 4.7).

Acid value Not more than 4.0 (Appendix 5.4).

Peroxide value Not more than 3.0 (Appendix 5.12).

Saponification value 188 to 198 (Appendix 5.7); use 2.5 g.

Alkaline impurities  Dilute 15 mL of water to 500 mL with  acetone and mix.  Add 2.5 mL of a 0.1 per cent w/v solution of bromophenol blue in ethanol (50 per cent) and mix again.  If the solution is blue or yellow instead of green, neutralize with 0.01 M hydrochloric acid or 0.01 M sodium hydroxide, respectively, to obtain a green solution (solvent mixture).  Melt 50 g of the sample at about 50º and mix thoroughly.  In a 150 mL conical flask, introduce 10.0 g of the melted substance and add 50 mL of the solvent mixture.  Stir vigorously and allow the two layers to separate.  Not more than 2 mL of 0.01 M hydrochloric acid is required to change the colour of the upper layer to yellow; this coloration must persist after vigorous stirring.

Composition of fatty acids  Carry out the test as described in the “Gas Chromatography” (Appendix 3.4).

      Test solution  Transfer about 100 mg of the sample, accurately weighed, to a 50-mL round-bottomed flask, and add 4 mL of 0.5 M methanolic sodium hydroxide.  Add a few boiling chips to the flask, connect the round-bottomed flask to a condenser, and reflux the mixture until the fat globules go into solution.  Add 5 mL of 2.0 M methanolic borontrifluoride to the boiling mixture via the condenser, and continue boiling for 2 minutes.  Add 2 to 5 mL of n-heptane for chromatography to the boiling mixture via the condenser, and boil for 1 minute.  Remove the flask from the source of heat, and remove the reflux condenser.  Add a saturated solution of sodium chloride, and swirl the flask gently.  Add more of the saturated solution of sodium chloride to bring the liquid level into the neck of the round-bottomed flask.  Transfer 1 mL of the organic layer into a glass-stoppered test tube, add sufficient amount of anhydrous sodium sulfate to remove the last traces of water, and filter.  Use the filtrate.

      System suitability solution  Prepare a solution containing 1 mg per mL each of methyl stearate and methyl oleate, in n-heptane.

      Chromatographic system

Detector  Flame ionization.

            Column  A fused-silica capillary column (15 m × 0.25 mm) bonded with a 0.25-µm layer of 25 per cent phenyl-25 per cent cyanopropyl-50 per cent methylsilicone.

Temperature

                COLUMN  The temperature programme is as follows:

 Carrier gas  Helium

            Flow rate  About 48 cm per second (1.4 mL per minute).

             Split ratio  60:1

(Note  The relative retention times are about 0.97, and 1.0 for stearate and oleate, respectively.)

      System suitability

            Sample  System suitability solution

      Suitability requirements

Resolution  Not less than 1.5 between stearate and oleate peaks.

            Relative standard deviation  The relative standard deviation of the peak area responses for the stearate and oleate peaks for replicate injections is not more than 5.0 per cent.

       Procedure  Inject about 0.1 µL of Test solution into the chromatograph, and record the chromatograms. Measure the peak areas of the methyl esters of the fatty acids.

       Calculation  Calculate the percentage content of each fatty acid methyl ester in the portion of Cocoa Butter taken by the expression,

(r_U/r_T)  100,

in which r_U is the response of each peak; and r_T is the sum of the responses of all of the peaks.

                Acceptance criteria See Table 1 below

Table 1