Leopold Hartman

The effect of unsaponifiable matter on the properties of coffee seed oil

The unsaponifiable matter of coffee seed oil has been shown to be responsible for the comparatively low melting-point (approximately 8C) of this oil. The melting point of coffee oil fatty acids, free of unsaponifiable matter, is 40−42C, and their esterification with glycerol produces an oil with a melting point of 34−36C. The unsaponifiable matter is probably responsible for high refining losses of coffee oil since the surface activity of its main constituents facilitates a partial saponification or emulsification of neutral oil during the treatment with alkalies, especially in oils with high acidity.

A study of rice bran oil refining

Examination of a number of rice bran oils revealed the presence of monoglycerides (0.5–1.4%) and other hydroxylated compounds such as diglycerides and glucosides. The hydroxyl numbers of the samples ranged from 8.5 to 27, depending on their acidity. On the assumption that the inordinately high refining losses of rice bran oil are due, along with the acidity, to the presence of hydroxylated compounds, the hydroxyl numbers of several samples of that oil were reduced by progressive acetylation with acetic anhydride. This was accompanied by gradual reduction of the refining losses, which seems to support the above mentioned assumption.

Further observations concerning effects of unsaponifiable constituents on the properties of coffee seed oil

The addition of monoesters of cafestol to triglycerides obtained by re-esterification of coffee oil fatty acids resulted in a behavior similar to that of the original coffee oil when subjecting the mixture to the Wesson procedure, a test for predicting refining losses. Contrary to expectation, the softening point of the triglycerides remained practically unaffected by the above addition.

Determination of hydroxyl value in fats and oils using an acid catalyst

A method for the rapid determination of the hydroxyl value of oils, fats and related products is described. The method uses toluene-p-sulphonic acid as a catalyst and this allows the sample, dissolved in toluene, to be acetylated in 10 min at room temperature. The fatty acid anhydrides formed during the acetylation are decomposed with aqueous sodium hydroxide and tert-butanol, and are then titrated with hydrochloric acid. The addition of an aliquot of the sample to the blank after the decomposition of the acetic anhydride reduces the number of titrations required to two.

About the conversion factor of phosphorus to phosphatides in soybean oil

The factor of 30 recommended by the official AOCS method Ca 12-55 for converting phosphorus to phosphatides in soybean oil is in reality a conversion factor to “acetone insolubles.” While applicable to crude soybean oils, its applications to degummed and refined oils is open to question. A corresponding revision of the method Ca 12-55 seems therefore indicated.

Determination of monoglycerides in crude oils and fats

The periodate oxidation method was adapted for the determination of small amounts of monolycerides present in natural oils and fats. The modification consisted in enriching the monoglycerides by extraction with 90% acetic acid saturated with boric acid in order to eliminate interfering substances prior to the reaction with periodate. A multifold concentration of monoglycerides originally present was achieved. This reduced the error of the standard periodate method to a minimum. Crude oils, such as soybean, rice bran, coconut, and palm, analyzed by the modified method showed monoglyceride contents considerably lower than those obtained by direct reaction of periodate with these oils.

Modified method for the determination of unsaponifiable matter in oils and fats

An inversion of the existing methods for the determination of unsaponifiable matter in oils and fats is proposed. The modified procedure consists in saponifying a 2–2.5 g sample of oil or fat with 2 mol l–1 ethanolic potassium hydroxide solution, dissolving the resultant mixture in 50 ml of pure cyclohexane, removing the soap by addition of 25 ml of water containing 0.5 g of sodium hydrogencarbonate and extracting the separated soap layer with 25 ml of cyclohexane. The combined cyclohexane layers are washed twice with 25 ml portions of 50% aqueous ethanol, cyclohexane is evaporated and the residue is dried in vacuo at 80 °C. Results obtained with the above procedure in the determination of the unsaponifiable matter in four different vegetable oils were in agreement with those given by the IUPAC standard hexane method II.D.5 with economy of solvents and operational time.