THE COMPONENT FATTY ACIDS OF GOAT MILK FAT

BY R. W. RIEMENSCHNEIDER AND N. R. ELLIS

(From the Animal Ilusbandry Division, Bureau of Animal Industry, United States Department of Agriculture, Washington)

(Received for publication, October 29, 1935)

Milk fats from different species of mammals are known to vary considerably in chemical composition. In early work, the butter fat constants were largely used to indicate the differences in com- position. More recently, emphasis has been placed on compari- sons of the component fatty acids of the various types of butter fats. The methods available for separation of the acids are not conducive to high precision. Their lack of uniformity, their dependence upon the manipulative technique, and upon the refine- ment of equipment have led to contradictory results and to differ- ences of opinion as to the presence of certain acids.

The distillation of the methyl esters is the most widely used method of effecting the separation of the components of butter fats. By the employment of this method and subsequent analyses of the distilled fractions, the presence of butyric, caproic, caprylic, capric, lauric, myristic, palmitic, stearic, and oleic acids in the fat of cow’s milk has been established without serious question. How- ever, from time to time, other acids have been reported. Smedley (l), in 1912, inferred the presence of a Cl0 unsaturated acid after he obtained a maximum in the iodine number of a Cl0 fraction in his distillation data. Crow’ther and Hynd (2), in 1917, on the other hand, attributed the unsaturation of the lower fractions of butter esters to be due to oleic acid. Griin and Wirth (3), in 1922, isolated decenoic acid from the lower boiling acids and established the position of the double bond as the (9, 10) position. Bosworth and Brown (4), in 1933, made a detailed study of the component acids of butter fat of cow’s milk in which they, too, found decenoic acid. In addition they presented evidence indicating the presence of a number of other acids; namely, tetradecenoic acid, a C&o, C&,

219

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220 Fatty Acids of Goat Milk Fat

or Cz4 acid containing two double bonds, acids of the arachidonic type probably belonging to the Cz2 series and a mixture of satu- rated acids of high molecular weight consisting principally of tetracosanoic acid and probably small amounts of behenic and cerotic acids. However, Hilditch and coworkers (5, 6) have reported, in addition to the commonly accepted acids, linoleic and arachidic acids. Eckstein (7) also reported the presence of lino- leic acid and added linolenic acid to the list of disputed acids.

Comparatively little work has been done on the composition of goat milk fat. Dhingra (S), in 1933, using the procedure devel- oped by Hilditch and coworkers (5, 6) reported the same acids present in goat milk fat as were reported by the latter in cow’s milk fat. The question of certain unusual characteristics in the fat of goat milk, which were concerned in the development of anemia in infants, has been suggested by a number of workers. De Rudder (9) has intimated that certain acids in goat milk fat may have a hemolytic action, producing anemia in infants, and Stoltz- ner (10) has stated that the high content of volatile acids has a definite effect upon anemia development. However, recent investigations,l of which the present report has formed a phase, have shown no differences between goat and cow’s milk in their hemoglobin-generating properties.

Human milk fat was found by Bosworth (11) to differ consider- ably in chemical composition from cow’s milk fat in that it con- tained linoleic and palmitoleic acids and very little of the volatile acids from butyric to capric. Although Bosworth did not isolate palmitoleic acid in pure form, he obtained evidence that indicated its presence. Since this acid has not been reported in the fat of cow’s or goat milk, there is a possibility that its presence may have been overlooked.

Lintzel has reported evidence (12) which shows that milk fat is produced in the mammary gland from glycerides taken from the blood stream. The question arises concerning the source of these glycerides, their precursors, and mode of formation. The fact that body fats are quite simple in comparison to butter fats and

1 Other phases of these investigations bearing on the nutritive value, composition, and physical properties of goat milk with comparisons to cow’s milk are in progress of publication as a technical bulletin of the United States Department of Agriculture.

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R. W. Riemenschneider and N. R. Ellis 221

can be greatly influenced by the character of the feed naturally gives rise to the question of how greatly the nature of the fatty acids of milk fat can be changed by the diet of the lactating animal.

The present paper reports the results of a study on the nature and composition of a composite sample of fat prepared from the milk of a goat herd kept on a regulated dietary regimen. Atten- tion was given to the identification and estimation of the approxi- mate amounts of each fatty acid normally present, especially the disputed acids. The findings of Bosworth and Brown (4) on the presence of hitherto unreported and the absence of certain other fatty acids in cow’s milk fat have prompted the use of their proce- dure in the present investigations. Their procedure differs from that used by Hilditch and coworkers (5, 6) in that the separation into liquid and solid acids is not made prior to the distillation of the methyl esters. The extensive series of distillation fractions obtained directly from the mixed esters enables a thorough exam- ination of the individual fractions.

EXPERIMENTAL

Source of Sample-The sample of goat milk fat consisted of 3.5 kilos of filtered butter fat obtained from a herd of twenty-four Saanen and Toggenberg does. Cream was obtained periodically from May to October, 1934, and churned while sweet. The por- tions of filtered butter fat were stored in a refrigerator until the required amount was collected. The goat does received a ration consisting of 1.5 pounds per day of a grain mixture of 8 parts corn, 4 parts oats, 2 parts wheat bran, and 1 part linseed meal, 3 pounds per day of alfalfa hay, and pasturage. The pasturage during May consisted of wheat and barley and thereafter of permanent pasture with access to an abundant growth of browse. From June 1 to July 15 the grazing period was limited to + hour per day and there- after unlimited except for milking periods.

Water-Soluble Acids-After saponification of the butter fat, the water-soluble acids were recovered and estimated by a proce- dure similar to that used by Hilditch and Jones (5). A total of 68.8 gm. of butyric and 7.5 gm. of caproic acids was accounted for from the 3.5 kilos of butter fat.

Preparation and Distillation of Methyl Esters of Insoluble Acids- The water-insoluble fatty acids were esterified with methyl alcohol

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222 Fatty Acids of Goat Milk Fat

and dry HCl. These methyl esters were then divided into three approximately equal portions and each portion was distilled into thirteen fractions, including the residue. Corresponding fractions from each portion were combined. The first ten of these com- bined primary fractions were redistilled, the residue from the lower boiling fraction always being added to the succeeding fraction. Since some decomposition and polymerization usually takes place during the distillation of the higher unsaturated esters, the last three of the combine@primary fractions were not redistilled. The distillations were carried out in a specially constructed electrically heated still similar in design and size to that described by Bush and Schwartz (13). An open tube column 10 mm. in diameter was used. A spiral of nichrome wires containing about 125 turns, wound so as to fit snugly within the walls of the column, and a smaller spiral of about the same number of turns wound in the opposite direction were employed to decrease the “channeling” of the vapors. A 100 cc. Bogert receiver was used to collect the primary fractions, while in the redistillation a Briihl receiver capable of collecting seven 50 cc. fractions was employed. The data from the 63 fractions obtained are given in Table I.

Examination of Distillation Data-The mean molecular weights of Fractions 1 to 3,6 to 9,14 to l&21 to 22,26 to 28,40 to 49, and 57 to 62 indicate the presence of Cg, Cs, Go, CIZ, C14, C16, and Cls saturated acids. From the constancy of the iodine numbers of the fractions mentioned, the presence of C1o, C14, C16, and Cl8 unsaturated acids seems likely. To indicate this more clearly a curve plotting iodine absorption of the fractions against their mean molecular weights was drawn. Those fractions whose mean molecular weights were nearly the same were treated as one fraction. The curve con- structed accordingly is shown in Fig. 1. Definite peaks of iodine absorption occur at the mean molecular weights of Co, C1+ C&, and Cl8 acid esters. The fractions of methyl esters were subjected to further study to obtain more definite proof of their fatty acid con- stituents.

Decenoic Acid-Fractions 4 to 17, after bromination in ether, were fractionally distilled, a Claisen flask with the side arm modi- fied to form a short electrically heated column insulated with asbestos cement being used. As shown in Table II, the analyses of the bromide obtained correspond to those of methyl dibromocap-

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R. W. Riemenschneider and N. R. Ellis 223

TABLE I

Data Obtained from Distillation of Methyl Esters of Mixed Fatty Acids and Analyses of the Fractions

Fraction No.

1 2 3 4 5 6 7 8 9

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39

Weight B.p.

gm. “C.

17.5 75- 77 17.7 77- 79 16.9 79- 83

8.1 84- 89 16.6 go-114 16.3 114-116 15.3 116-119 13.7 119-120 12.4 120-125 13.6 126-132 12.2 132-140 11.2 140-144 11.7 144-150 44.0 81- 82 46.1 82 42.1 82 47.2 82- 84 42.0 84- 89

6.2 go- 91 46.7 91- 97 50.8 98-103 41.7 103-117 41.1 119-120 30.6 120 40.5 120-123 42.6 123 37.9 123-124 37.2 124 40.5 124-126 28.8 126 40.3 126-130 34.7 130-136 40.3 136 43.6 136 40.2 136 43.7 136 39.1 136 46.3 136 43.5 136

PIeSSUrt!

mm.

75 75 75 75 75 75 75 75 75 75 75 75 75

l-2 l-2 l-2 l-2 l-2 l-2 l-2 l-2 l-2 l-2 l-2 l-2 l-2 l-2 l-2 l-2 l-2 l-2 l-2 l-2 l-2 l-2 l-2 l-2 l-2 1-2

Acid series I No.

C6 130.7 0.2 C6 130.7 0.2 C6 130.8 0.2 C6&S 134.2 0.7 C6FC.2 149.5 0.8 CS 156.2 0.4 CS 156.4 0.3 C8 158.1 0.6 C8 159.6 0.5 cd& 161.8 0.7 C8-clO 167.8 1.4 cs-Cl0 173.8 2.5 c8-clo 181.4 2.6 C 10 183.8 2.0 C 10 184.6 2.2 Cl0 185.4 3.1 C 10 186.0 3.3 Cl0 188.0 3.2 Cleclz 192.0 3.5 clo-cl2 203.8 3.4 clo-c12 210.5 3.5 crcu 218.7 3.7 ckc14 231.4 3.2 G-C14 235.6 3.9 cn-Cl4 237.5 3.8 Cl4 241.3 3.0 Cl4 241.5 3.5 Cl4 241.7 4.7 CM-CM 244.4 4.0 Cd& 247.3 4.1 CM-CM 252.0 5.9 CA&16 257.2 5.7 CI4J& 260.6 6.0 CM-Cl6 263.6 6.9 CL-CM 263.8 7.0 CL-Cl6 266.1 7.3 c14-Cl.5 266.5 6.7 Cl&16 267.6 6.8 G-G 267.9 6.9

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224 Fatty Acids of Goat Milk Fat

TABLE I-Concluded

Fraction NO. Weight B.p. PESSUE3 Acid series MertIl

mol. wt.

0m. “C. mm.

47.4 136 l-2 Cl6 42.1 136 l-2 Cl6 44.3 136 l-2 CM 41.8 136 l-2 Cl0 48.9 136-138 l-2 Cl6 45.1 138-140 l-2 Cl6 47.9 140-142 l-2 Cl6

52.0 142 l-2 Cl6 42.2 142 l-2 Cl6 42.9 142 l-2 Cl6

44.3 142-145 l-2 Clf7C,8 40.7 145 l-2 crc1.3 39.4 145 l-2 C16dh 43.6 145-150 l-2 c16-c18 42.7 150 l-2 crCL8 44.3 150 l-2 c16-Cl.3 48.8 150-152 l-2 Cl6418

38.9 152 l-2 G-G 8

42.2 152 l-2 Cl&18 39.4 152 l-2 GrC18 65.9 * l-2 cd&

325.0 152-157 l-2 Cle-CI 8

393.6’1 158-162 l-2 Cl8 501.0$ Residue l-2

* Residue from redistillation of tenth primary fraction. t Fractions 11 and 12 of primary distillation. $ Residue from primary distillation, not distilled.

40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63

-

_-

-

268.9 6.3 269.1 7.4 269.2 7.4 269.8 7.9 270.3 8.7 270.3 10.2 270.4 7.8 270.4 8.9 271.4 10.3 271.6 12.0 272.6 14.3 273.6 18.0 275.1 19.9 279.1 32.4 280.2 38.0 284.6 51.2 286.8 59.0 291.2 71.4 291.2 71.5 291.3 69.8 292.0 60.3 290.7 62.5 295.0 65.1

I No.

rate (theory, Br 46.13 per cent). After debromination with Zn dust and alcohol, followed by saponification, subsequent acidifica- tion and extraction, 1.4 gm. of material were obtained whose analyses, as given in Table II, compared favorably with the theory for decenoic acid (mean mol. wt. 170.2, iodine number 149.3). Grim and Wirth (3) and Bosworth and Brown (4) have reported comparable values.

Tetradecenoic Acid-Fractions 18 to 30 were subjected to the same treatment as above. However, the original fraction of the dibromides obtained was still impure, as indicated by the boiling point and bromine content. The fraction was debrominated and

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R. W. Riemenschneider and N. R. Ellis 225

25

24

23

22

21

20

19

18

17

16

g I5 I I

-!H i i I i

---I i

I i : i : i

i

I H/d. 1 a:~~-~~~~~~~~ I “170 190 210 230 250 270 290

180 200 220 240 260 280 300 MEAN MOLECULAR WEIGHT OF METHYL ESTER

FIG. 1. Iodine absorption in relation to the mean molecular weight of the methyl ester fractions. Curve 1, iodine absorption per fraction; Curve 2, iodine absorption per fraction f 10; Curve 3, iodine absorption per fraction f 100.

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226 Fatty Acids of Goat Milk Fat

the reprepared methyl esters were fractionally distilled. Three fractions were obtained, the middle one (mean mol. wt. 239.7, iodine number 89.2) after rebromination and distillation yielded a fraction (b. p. 140-145”, 0.5 mm.) whose bromine content, as given in Table II, agreed within 1 unit per cent of the theoretical value of 39.95 per cent for methyl dibromomyristate. The values for molecular weight (225.2) and for iodine number (110.6) of the material recovered after debromination agreed well with the theoretical values for tetradecenoic acid (mol. wt. 226.3, iodine

TABLE II

Examination of Unsaturated Acids, Their Methyl Esters, and Bromine Addition Products Obtained from Fractions 4 to 48

0 A

8 pi

Compound B.p. 2 2

2 F; '2 g%

M gc g2

c? z i

8 8 L-4 ---

*c. mm,. PW cent Methyl dibromocap-

rate................. 120-123 0.5 44.021.4925 Decenoic acid. . 155-158 14.0 173.0 1.4468147.9 Methyl dibromomyri-

state................ 140-145 0.5 38.961.4890 Myristoleic acid (tetra-

decenoic) 183-186 14.0 225.2 1.4558 110.6 Methyl dibromopalmi-

tate 165-170 0.5 37.24 1.4857 Methyl palmitoleate . 110-111.5 0.5268.1 1.4498 94.0 Palmitoleic acid (hexa-

decenoic). Obtained from ester 253.5 1.4587 99.4 by saponification

number 112.2). Bosworth and Brown (4) reported values for the dibromide which are in good agreement with the values reported here.

Palmitoleic Acid-As already indicated, no data have been reported on the presence of palmitoleic acid in the milk fat of the cow or goat. However, the distillation data suggested its presence and confirmatory work was accordingly undertaken.

Fractions 34 to 48, when combined and subjected to the lead salt- alcohol separation, yielded a “liquid” acid fraction with a mean

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R. W. Riemenschneider and N. R. Ellis 227

molecular weight of 261.9 and iodine number of 69.5. The methyl esters of this fraction were fractionally distilled into two portions: Fraction A, boiling range of 116122” at 0.5 to 1.0 mm. pressure and Fraction B, boiling range 122-135” at 0.5 to 1.0 mm. pressure. Fraction A was brominated in anhydrous ether at 0” and after removal of the ether the residue was fractionally distilled. A fraction of 14.0 gm., the bulk of which distilled sharply at 170” at 0.5 mm. pressure, proved to be nearly pure methyl dibromopalmitate. This bromide was a heavy amber- colored liquid, nE” = 1.4587, and contained 37.24 per cent bromine as compared to the theoretical percentage of 37.35. After deter- mination, the reesterified recovered material was distilled, yield- ing 8.5 gm. of nearly pure methyl palmitoleate, as indicated by the data given in Table II.

The acid obtained from the ester fraction also gave values (Table II) in good agreement with theory. Upon hydrogenation of a portion of the acid with Pd-BaSO1 used as catalyst, the crystallized product gave the accepted value of 62.5” for the melt- ing point of palmitic acid. The data establish without doubt the presence of palmitoleic acid in goat milk fat.

Oleic Acid-The presence of some oleic acid accompanying the palmitoleic acid in the fractions reported above was demonstrated by further examination of Fraction B with a boiling point of 122- 135” at 0.5 to 1.0 mm. pressure. Upon redistillation, a fraction of 5.1 gm. was obtained, which had a mean molecular weight of 287.5 and an iodine number of 89.2. A portion of the acids obtained from this fraction, after hydrogenation with Pd-BaSOc as catalyst, yielded a saturated product which after several crystallizations gave the following analyses: molecular weight 284.2, melting point 68.9. Stearic acid, the hydrogenation product of oleic acid, has a molecular weight of 284.3 and a melting point of 69.3’. The presence of oleic acid was also established in later fractions, incidental to a search for higher unsaturated acids.

Linoleic Acid-Since the boiling points of methyl oleate and methyl linoleate are nearly identical, the fractions containing the bulk of the methyl oleate should also contain methyl linoleate if that ester were present. Accordingly, Fractions 57 to 62 were subjected to lead salt-ether separations. The mean molecular weights of the liquid acids from Fractions 57 to 61 ranged from

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228 Fatty Acids of Goat Milk Fat

281.6 to 283.3 and the iodine numbers from 88.8 to 91.8; the liquid acids of Fraction 62 had a mean molecular weight of 284.2 and an iodine number of 99.1. These unsaturated fractions were bromi- nated in anhydrous ether at 0’. Traces of ether-insoluble bro- mides were obtained from Fraction 61 and a larger amount (0.264 gm.) from Fraction 62. The weights of the samples taken for lead salt separations range from 6.4 to 7.0 gm. These insol- uble bromides proved to be identical and had an average bromine content of 67.6 per cent, which corresponds closely with the theoretical amount of 67.8 per cent for octabromoarachidic acid. The bromides blackened at 230-232” without showing a definite melting point.

The ether was removed from each of the above brominations by distillation and low boiling petroleum ether added. The bromides dissolved completely and the solutions were stored in the refrigera- tor at O-5”. After several days storage no crystals of tetrabro- mide were obtained. A slight precipitate was obtained from Fraction 62, which proved to be octabromides.

While traces of linoleic acid may possibly have been present in the sample investigated, the data agree with that of Bosworth and Brown on cow’s milk fat in support of the conclusion that this acid was not present in appreciable amounts.

Highly Unsaturated Acids in Fraction BS-Fraction 63, the un- distilled residue from the primary distillation, had a dark red coloration. Determination by the modified Kerr-Sorber method (14) showed the presence of 0.13 per cent of unsaponifiable mate- rial as a residual product from the entire sample of butter fat.

The fatty acids of Fraction 63 were subjected to the lead salt- alcohol separation and the liquid acids converted to their methyl esters and fractionally distilled. The fractions obtained upon bromination yielded both ether-insoluble and ether-soluble bro- mides. The results given in Table III show a very close agree- ment between the average bromine content of the ether-insoluble bromides (66.7 per cent) and the theory for methyl octabromo- arachidate (66.8 per cent). The melting point, indistinct though it was with blackening at 228’, is in agreement with the observa- tions reported. Undoubtedly arachidonic acid was present in the sample.

The small amount of bromides (0.60 gm.) soluble in ether but

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R. W. Riemenschneider and N. R. Ellis 229

insoluble in petroleum ether represents all that was obtained from the entire sample. The bromine content (64.2 per cent) agrees with the theory for the methyl ester of a CZz acid octabromide (64.9 per cent) more closely than for methyl octabromoarachidate. This bromide was a pale orange, soft, amorphous, light powder, whereas methyl octabromoarachidate is a hard, nearly white, somewhat granular material. Bosworth and Sisson (15) reported evidence indicating that the octabromoarachidate as usually obtained (m. p. 228-230’) is a mixture of at least two isomers. They obtained fractions of these bromides melting at 162’, 208”, and 262” from butter fat from cow’s milk. No evidence of the presence of linoleic acid was found in Fraction 63.

TABLE III

Data Obtained from Distillation of Methyl Esters of Liquid Acids of

63-a 63-b 63-c

Weight

gn.

149. I 121.6

58.2

-

.I il !I -

-~ “C.

132-135 292. I .35-145 300. ( .45-180 316. (

Fraction 63

INo. 1 !

1 Weight1 M.P. 1 ,!$z, 1 Weight 1 M.p. / tfz, __-__-- --

gm. “C. per cent g?n. “C. per cent

89.5 0.40 228 66.3 None 92.7 0.87 228 67.0 “

105.5 2.96 228 66.7 0.60 148-150 64.2

Saturated Acids from Butyric to Xtearic Acid-Little difficulty was encountered in isolating in pure form the acids of even number of C atoms from caproic to stearic from those fractions whose molec- ular weights approached closely the theoretical value for their esters. The accepted values for the melting points of caprylic, capric, myristic, palmitic, and stearic acids were obtained after a single crystallization. However, it was necessary to redistil the fractions containing methyl laurate in order to obtain the acid of accepted melting point 43.6”.

Butyric acid was isolated from the water extract of the total mixed acids. Caproic acid, obtained from Fractions 1, 2, and 3, boiled at 200-202’.

Saturated Acids of Higher Molecular Weight Than Xtearic Acid- The analyses of the saturated acids obtained from the lead salt-

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230 Fatty Acids of Goat Milk Fat

alcohol separation of the fatty acids of Fraction 63, following a crystallization from alcohol, gave the first indication of the pres- ence of saturated acids of high molecular weight. A total of 159.7 gm. of solid acids with a mean molecular weight of 290.2 and an iodine number of 1.6 was obtained.

The methyl esters of these acids were fractionally distilled from a Claisen flask, modified as previously described. The results of the distillation and mean molecular weights of the fractions are

TABLE IV

Distillation of Methyl Esters of Solid Fatty Acid Obtained from Lead Salt-Alcohol Separation of Fraction 63

Fraction No.

63-a 63-b 63-c 63-c 63-d 63-e 63-f 63-g 63-h 63-h-a? 63-h-b

1

_-

B.P. at 1 mm. Weight

“C. cm.

135-142 27.1 142 30.5

142 36.9 142 33.0 142-144 25.7 144-150 7.2* 150-155 2.1 Residue 4.7 170-180 3.6 Residue 0.13

1

297.0’

299.2

> 297.0

298.3

298.6,

303.6 319.2 377.6 381.2 412.8

Crystalliaation of acids

Mean mol. wt. M.p.

“C.

284.5 69.3

286.5 321.0 378.9 368.7

68.0-68.5 66.3-67.0 74.1-74.3 74.5 78.0

* 5.1 gm. of impure stearic acid (mean mol. wt. 286.5, m.p. 6S.0-6S.5°) were obtained from this fraction as first crop; 1.9 gm. of crystals (mean mol. wt. 310.2, m.p. 66.0-66.5’) were obtained from the mother liquors.

t The acids from Fraction 63-h after crystallization (mol. wt. 378.9) were esterified and distilled to give Fractions 63-h-a and 63-h-b.

given in Table IV. Fractions 63-a, 63-b, 63-q 63-d, and 63-e, because of their similar boiling points and molecular weights, were combined. The acids obtained from these fractions after one crystallization had a mean molecular weight of 284.5 and a melting point of 69.3’, which indicate nearly pure stearic acid. Fraction 63-f (Table IV) upon crystallization yielded 1.9 gm. of acids with a mean molecular weight of 310.2 and 5.1 gm. of impure stearic acid, which had a mean molecular weight of 286.5 and melted at 68.0-68.5".

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R. W. Riemenschneider and N. R. Ellis 231

Because Fraction 63-g was comparatively small and the preced- ing fraction was largely stearic acid, it was considered doubtful if any CzO or Czz saturated acids were present, in more than traces. This view was also supported by the abrupt increase in molecular weight of Fraction 63-h and also by the low melting point of the higher molecular weight fraction obtained from Fractions 63-f and 63-g.

The mean molecular weights of the acids obtained from Frac- tion 63-h indicated a mixture of Cz4 and a higher acid, probably cerotic acid. The results of the analyses of Fractions 63-h-a and 63-h-b confirmed this view. The results of these analyses on Fraction 63 indicate that the saturated acid consisted principally of stearic acid, along with small amounts of lignoceric acid (CX4HJ80.J and traces of cerotic acid (C2~H6202). The presence of arachidic acid (Cz0H4002) or behenic acid (C22H440.J is questionable.

Estimation of Component Fatty Acids-In distillations of mixed saturated and unsaturated esters, it has been observed that the unsaturated acids are distributed chiefly with the fractions con- taining saturated acids of 2 less carbon atoms and of the same number of carbon atoms.

In the present work the assumption has been made that the unsaturation of Fractions 1 to 18 was due to methyl decenoate, Fractions 19 to 28 to methyl tetradecenoate, Fractions 29 to 49 to methyl palmitoleate, Fractions 50 to 59 to methyl oleate, and Fractions 60 to 63 to methyl oleate and methyl arachidonate. This assumption was, in general, supported by the findings re- ported. The calculations of the unsaturated components of Fractions 60 to 62 were based on the iodine numbers of the un- saturated acids as obtained by the lead salt-ether separations. The calculations of the unsaturated acids of Fraction 63 were based on the results reported in Table III.

After the amounts of unsaturated esters in a given f,raction were calculated, the saponification number of the saturated esters in that fraction was calculated, from which the saturated compo- nents were deduced on the assumption that not more than two are present.

The results of the calculations are given in Table V. Since decenoic and tetradecenoic acids are present in very small amounts, the assumption made for their calculation should not seriously affect the other components.

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232 Fatty Acids of Goat Milk Fat

Results of the calculations which are given in Table V show excellent agreement with those obtained by Dhingra (8) in his work on milk fat from Indian goats with the method developed by Hilditch and coworkers (5, 6) for most of those acids present in considerable amounts. However, it should be recalled that he does not report decenoic, tetradecenoic, palmitoleic, and arachi- donic acids and does report some linoleic acid, whereas its presence

TABLE V Component Fatty Acids in Entire Sample of Goat Milk Fat

Acid

Butyric . . . . . . . . . Caproic . . . . . . . . . . Caprylic. . . . . . . . . . Capric.. . . . . . . . . . . . . Laurie.. . . . . . . . . . . Myristic.. . . . . . . . .

Palmitic.. . . . . . . . . . Stearic . . . . . . . . . . . . Saturated acid of

higher mol. wt. than stearict . . . .

-

I?

_-

-

Per {eight* “$

weight --

gm. 69.3 2.1 63.8 1.9 88.3 2.7

261.0 7.9 114.8 3.5 336.0 10.2

943.0 28.7 265.2 8.1

14.6 0.4

Acid wiel

C4 CfJ CS Cl0 Cl2 Cl4

Cl6 C 18

Cl8

Unsaturated

Acid Per

Weight* “,$ weight

-- Bm.

Decenoic . . . . . . . . . 5.4 0.2

Tetradecenoic . . . . . 12.9 0.4 Hexadecenoic (pal-

mitoleic) . . . . . . . . 68.2 2.1 Oleic.. . . . . . . . . . . 1028.0 31.2 Arachidonict and

(C,,?). . . . . . . . . . . 23.0 0.7

* Corrected to complete recovery. i Calculated as tetracosanoic (lignoceric), since the examination of

Fraction 63 indicated that this acid is present in greater amount than arachidic or cerotic acid.

$ Calculated as arachidonic acid although evidence of a C&Z acid contain- ing four double bonds was found.

was not detected in the present work. Dhingra also reported arachidic acid present, whereas the evidence found in this investi- gation indicates lignoceric rather than arachidic acid.

SUMMARY

A composite sample of fat from goat milk, consisting of 3.5 kilos, was converted to methyl esters, and fractionated into 63 fractions for determination of the component fatty acids.

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R. W. Riemenschneider and N. R. Ellis 233

A study of the distillation data indicated the presence of decen- oic, tetradecenoic, palmitoleic, oleic, caproic, caprylic, capric, myristic, palmitic, and stearic acids. Subsequent examination of the fractions established the presence of these acids and also of arachidonic acid.

Traces of an octabromide of an unknown acid were found (prob- ably a C&Z acid or an impure isomer of arachidonic acid).

A mixture of saturated acids with higher molecular weight than stearic acid was isolated, consisting principally of tetracosanoic acid along with traces of cerotic acid.

Estimations on the content of the component fatty acids present show general agreement with previously published analyses except for the absence of linoleic acid and the presence of small percent- ages of decenoic, tetradecenoic, and hexadecenoic acids in the sample.

BIBLIOGRAPHY

1. Smedley, I. P., Biochem. J., 6,451 (1912). 2. Crowther, C., andHynd, A., Biochem. J., 11,139 (1917). 3. Grtin, A., and Wirth, T., Ber. them. Ges., 66,2197 (1922). 4. Bosworth, A. W., and Brown, J. B., J. Biol. Chem., 103,115 (1933). 5. Hilditch, T. P., and Jones, E. E., Analyst, 64, 75 (1929). 6. Hilditch, T. P., and Sleightholme, J. J., Biochem. J., 24, 1098 (1930);

26, 507 (1931). 7. Eckstein, H. C., J. Biol. Chem., 103, 135 (1933). 8. Dhingra, D. R., Biochem. J., 27,851 (1933). 9. de Rudder, B., Klin. Woch., 3,876 (1924).

10. Stoltsner, W., Mtinch. med. Woch., 69,4 (1922). 11. Bosworth, A. W., J. BioZ. Chem., 106,235 (1934). 12. Lintzel, W., Tierzticht. u. Ziichtungsbiol., 29, 219 (1934). 13. Bush, M. T., and Schwartz, A. M., Ind. and Eng. Chem., 4,142 (1932). 14. Jamieson, G. S., Vegetable fat and oils, American Chemical Society

monograph series, New York (1932). 15. Bosworth, A. W., and Sisson, E. W., J. BioZ. Chem., 107,489 (1934).

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R. W. Riemenschneider and N. R. EllisGOAT MILK FAT

THE COMPONENT FATTY ACIDS OF

1936, 113:219-233.J. Biol. Chem. 

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