MAY 15, 1936
-4NALYTICAL EDITION
I n Table V three different quantities of ammonia nitrogen were added to aliquots of two lots of pooled yolk. The recovery of the ammonia nitrogen was deemed satisfactory in all cases. The period of 1.5 hours a t 38" C. was used for the experiments reported in Tables IV and V and for results reported below.
v.
RECOVERY O F AMMONIA NITROGEN FROM EGG TABLE YOLK CONTA41NING VARYING ADDITIONSOF AMMONIUM
Estimation of Oleomargarine in Ice Cream T. H. W-HITEHEAD AND J. B. DUNSON University of Georgia, Athens, Ga.
SULFATE
(Results expressed as milligrams of ammonia nitrogen per 100 cc.) No. of Determined on Added Calculated .4ctually Detns. Yolk Alone t o Yolk Total Determined 5.28 5.23 4 3.47 1.81 4.30 4.40 4 2.49 1.81 6.85 6.76 4 3.47 3.38 5,87 5.80 4 2.49 3.38 4 3.47 4.73 8.20 8.23 7.22 7.39 4 2.49 4.73
In the procedure for egg white described above, the directions specify the use of liquid white. Firm white could also be used, but the liquid white is much easier to pipet and mix with the carbonate solution than the firm white and has the same percentage of ammonia nitrogen for the same egg. This is ~ h o w nin Table VI, where the values for the three distinct layers of egg white for four eggs are given. All the results are within experimental error. I n practice it was found satisfactory to slit the firm white envelope and pipet from the mixture of outside and inside liquid white.
TABLE VI. DISTRIBUTION OF AMMONIANITROGEN IN Eaa WHITF. (Results expressed as milligrams of ammonia nitrogen per 100 cc.) Outside .Liquid Inside Liquid Egg White Firm White White 1 0.12 0.10 0 11 2 0 14 0.18 0 21 0 18 0.12 3 0.12 4 0 20 0 21 0 20
I n a large number of eggs of similar history the ammonia nitrogen was determined for both white and yolk by the aeration and absorption methods. Both methods were not applied on the same samples. Reference to Table VI1 shows that in general there was satisfactory agreement between the values obtained by the two methods for both white and yolk on material of similar nature. O F THE ANALYSIS TAElLE VII. COMPARISON OF RESULTS OF EGGS BY AERATION AND ABSORPTION METHODS
Method
Material
&44)ration
White Yolk White Yolk .Mixed whole egg
Absorption
No. of Ammonia Standard Samples Nitrogen Deviation Mg./IOO cc. 83 0.24 0.086 83 2.30 0.287 16 0.35 0.137 301 2.41 0.280 6 0.87 0.003
Acknowledgment The eggs used in this study were kindly supplied by the Poultry Section of the Experiment Station.
Literature Cited (1) Conway, E. J., and Byme, A., Biochem. J.,2 7 , 4 1 9 (1933). (2) Hendrickson, N., and Swan,G. C., J. IND. ENG.CHEM.,10, 6 1 4 (1918). (3) Holst, W. F., and Slmquist, H. J., Hzlgurdiu, 6 , 4 9 (1931). (4) Sharp, P. F., and Powell, C. K., IND.ENO.CHEM.,22, 905 (1930). (5) Thomas, -4.W., and Van Hauwaert, M. A., Zbid., Anal. Ed., 6 , 338 (1934). RECEIVE^) February 8 , 1936. Published with the permission of the Director of the Experiment Station as Journal Article 251 (n. a,).
203
A method for determining the percentage of oleomargarine and butter fat in ice cream is given, which consists of a modified Roese-Gottlieb extraction procedure combined with a modified Reichert-Meissl procedure. Formulas are derived for calculating the percentage of oleomargarine in the extracted fat, the fat being calculated in the usual manner.
T
HE lower price of ole-margarine as compared to butter fat a t present has led some manufacturers of ice cream
to substitute oleomargarine to some degree for butter fat. This may soon bring about serious consequences; it is illegal in many states and some investigators (3) have shown that ice cream made of olecmargarine is deficient in certain vitamins. It would seem obviously unfair to sell as ice cream a product that is not made of butter fat, but any ruling of fair trade competition must first have some basis for classification. This problem led the authors to work on a method for determining the relative amounts of oleomargarine and butter fat in ice cream with a reasonable degree of accuracy. The problem is more difficult than it first seemed, Modern homogenizing equipment has made microscopic examination and staining almost useless as a means of detecting oleomargarine, and refractive index and specific gravity gave no suitable quantitative data. The iodine value gave qualitative indication, but because of the diversity of oleomargarines on the market did not give quantitative confirmation. The Kirschner-Flanders (4)method did not give quantitative results when tried on the authors' samples. The usual Reichert-Meissl method (1)was also soniewhat unsatisfactory and gave erratic results. However, it was found that if the Roese-Gottlieb extraction procedure and the Reichert-Meissl procedure were slightly modified, a precise method was obtained.
Experimental
APPARATUS. The usual apparatus for determining the fat percentage in butter was used (6). REAGENTS. Oleomargarine was furnished by the Joseph Costa Co., Athens Ga., and had the following composition: 70 Total fat Oleic oil Neutral oil Cottonseed oil Moisture Salt Milk solids
34 34
15
% 83
12 3 2
Ammonium hydroxide, ethyl alcohol, diethyl ether, and petroleum ether as given by the method of the Association of Official Agricultural Chemist (2). Sulfuric acid: 31.5 cc. of acid (sp. gr. 1.83) per liter.
INDUSTRIAL AND ENGINEERING CHEMISTRY
204 90
I
80
TABLE I. REICHERT-MEISSL VALUESOF EXTRACTED FAT
PER C E N T B U T T E R FAT 70 60 $0 40 30
20
lo
0
Sample
Butter Fat
Oleomargarine
%
%
100.0 80.72 76.74 65.67 56.33 32.36 0.00
0.00 19.28 24.26 44.33 44.67 67.64 100.00
Reichert-Meissl Value 30.96 24.96 23.24 16.65 16.45 10.02 0.38
Duplicate determinations on butter fat varied *0.1 in the Reichert-Meissl value and * 0.03 on oleomargarine duplicates. Taking 30.96 and 0.38 as reliable averages and the slope of the curve in Figure 1 as 0.31, it was possible to obtain a formula by substitutions in the classical equation for a straight line, y = mx b, where m is the slope a n d b a constant.
+
50 0
VOL. 8, NO. 3
IO
20
30
44
PER CENT
50
60
70
80
io
100
OLEOMARGARIN€
FIGURE 1. RELATIONOF REICHERT-MEISSL VALUE TO PERCENTAGE OF OLEOMARGARINE AND BUTTERFATIN ICE CREAM
Procedure EXTRACTION OF FATFROM ICECREAM. The ice cream is al-
lowed to soften at room temperature. The fat soon separates and rises to the top, and the sample is then thoroughly mixed with an egg beater or other mechanical stirrer. Aliquot portions of about 100 grams each are accurately weighed and the fat is extracted by using 12.5 cc. of ammonium hydroxide solution, 50 cc. of ethyl alcohol, 100 cc. of diethyl ether, and finally 100 CG. of petroleum ether. After the addition of each the mixture is thoroughly agitated in the separatory funnel for 30 seconds, and is then allowed to stand for 20 minutes, before separating the layers. As much as possible of the etherfat solution is drawn off into a flask through a small, quick-acting filter. A second extraction, with 100 cc. of each ether, is necessary to insure complete removal of fat. The clear solution is drawn off through a small filter into the same flask; and the tip of the separatory funnel, the filter, and the funnel are washed with a few cubic centimeters of a mixture of equal parts of the two ethers, free from suspended water. The greatest portion of ether is distilled off, and the fat is dried in an oven a t 90’ C. to constant weight. The flask is weighed with a similar flask as a counterpoise. The fat is now ready for use, and can conveniently be handled a t about 40’ C. (A volume of about 5.5 cc. at this temperature weighs about 5 grams.) After samples have been taken from the flask, the fat is completely removed with petroleum ether. The weight of the dried flask with residue is deducted to obtain the weight of the fat.
Determination Weigh out accurately a sample of about 5 grams of extracted fat in a tared glass vessel, add 10 cc. of ethyl alcohol and 2 cc. of sodium hydroxide solution, and saponify on a water bath (usually 1 hour). Allow the flask to cool to room temperature after all alcohol has evaporated, taking care to prevent any loss of soap. The last traces of alcohol can be removed by waving the cool flask to and fro, mouth down. Dissolve the soap in 100 cc. of recently boiled distilled water and transfer to a 250-cc. distilling flask. Heat the flask up to 60’ to 70’ C. and add 40 cc. of sulfuric acid solution. Drop in a few pieces of pumice stone and connect to the condenser. Warm the flask until the fats separate as a clear layer, then continue the heating until 110 cc. of distillate have been collected in a graduated cylinder. The time of distillation should be between 28 and 32 minutes. Titrate a 100-cc. portion of the distillate with standard 0.1 N sodium hydroxide solution, using phenolphthalein as indicator. The ReichertMeissl value is calculated from the usual formula. Reichert-Meissl value =
cc. of NaOH X 1.1 X 5 grams of sample
The procedure followed was to make u p samples of ice cream varying from 100 to 0 per cent of butter fat and from 0 to 100 per cent of oleomargarine, and to analyze these according to the procedure outlined above. The results are given in Table I and Figure 1.
Per cent of oleomargarine in fat = 30.96 - Reichert-Meissl value (1) 0.31 Per cent of butter fat in fat = 100 - per cent of Reichert-Meissl value - 0.38 oleomargarine = (2) 0.31 Since the variation in 0.38 is greater than that in 30.96, it is safer to subtract from 100 per cent to get butter fat. To test this formula, samples of varying composition were prepared and submitted for analysis to Mr. Dunson, who did not know their composition. The results are shown in Table 11.
TABLE 11. ANALYSES OF UNKNOWN SAMPLES
Oleomargarine Butter fat Oleomargarine Butter fat Oleomargarine Butter fat
Sample 1 1 2 2
3 3
ReichertTbeoretiMeiaal Calculated oal DeviaValue Percentage Percentage tion 6.57 82.0 83.0 -1.0 5.57 18.0 17.0 $1.0 13.25 57.1 57.2 -0.1 13.25 42.9 42.8 +0.1 27.45 11.3 12.0 -0.7 27.45 88.7 88.9 +0.7
The percentage of fat may be calculated as.usua1. Per cent of fat in ice cream
=
grams of fat x 100 grams of ice cream
The composition of this fat is then calculated by Formulas
1 and 2. The grams of oleomargarine and butter fat can b e calculated easily and the percentage of oleomargarine in the original ice cream sample found by substituting grams of oleomargarine for grams of fat.
Discussion Although this paper offers no new qualitative differentiation between butter fat and oleomargarine, i t does offer a more exact quantitative determination, accomplished by standardizing the extraction method for ice cream, and by increasing the strength of the sulfuric acid in the usual Reichert-Meissl procedure. I n this way more reliable results were obtained. Only vanilla ice cream was used, but the method should apply to other flavors, particularly chocolate, caramel, and nut flavored ice cream. The precision and accuracy are evident from the data presented.
Literature Cited (1) Allen’s Commercial Organic Analysis, 5th ed., Vol. 11, Philadelphia, P. Blakiston Son’s Co., 1924. (2) Assoo. Official Agr. Chem., Official and Tentative Methods of Analysis, 1930. (3) Ellis, “Hydrogenation of Oils,” p. 355, New York, D. Van Nostrand Co., 1919. (4) Flanders and Truit, IND. ENG.CHEM.,Anal. Ed., 6,286 (1934).
RECEIVED February 8,
1936.
