A Method for the Detection of Foreign Fats in Dairy Products

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Abstract
Ten g. of melted fat was weighed into an Erlenmeyer flask, 100 ml. of hot absolute ethanol added, the clear soln. cooled to room temp. and kept at 20[degree]C. for 2 hrs. The precipitate was washed with 10 ml. ethanol, freed from solvent under vacuum and its refractive index detd. at 40oC. A 10 ml. aliquot of the filtrate or alcohol soluble fraction was transferred to a small tared petri dish, freed of solvent, weighed and its refractive index detd. Five ml. of 0.001% Na methoxide was added to 75 ml. of the remaining filtrate and after 1 hr. of ethanoly-sis neutralized with dilute phosphoric acid. The ethyl es''ters were extracted with ethyl ether from 50 ml. of the clear filtrate and their refractive index also detd. at 40[degree]C. Admixtures of butterfat and 10 % of various substitute fats had different solubilities in ethanol and different refractive indices and rates of ethanolysis from pure butter fat. Twenty different samples of authentic butter-fat contained 70 [plus or minus] 4% of alcohol soluble triglycerides at 20oC. The alcohol insoluble fraction had an avg. refractive index of 1.4542 which was significantly different from 1.4550 the avg. value of an admixture of butterfat containing 10% of substitute fat other than coconut oil. The addition of 20% coconut oil significantly lowered the refractive index of the alcohol soluble fraction of butterfat from 1.4540 to 1.4532.

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