54
INDUSTRIAL A N D ENGINEERING CHEIWISTR Y
*
Vol. 16, No. 1
Chemical Constituents of Pecan Oil' By Paul D. Boone BUREAUOF
PL.4NT I N D U S T R Y , W A S H I N G T O N ,
IKCE 1918 the Division of Soil Fertility Investigations, Bureau of Plant Industry of the Department of Agriculture, has conducted fertilizer investigations with pecans. Experiments following the triangle system of fertilizer experimentation2 have been conducted upon the principal soil types of the pecan belt of Georgia, Florida, and Alabama. In addition to finding out the fertilizer requirements of the various soil types for pecans, a laboratory investigation has been made to determine the influence of phosphorus, nitrogen, and potash fertilizers on the filling quality, protein, oil, and carbohydrate content of the kernel. The results of some of these studies have been given in an earlier paper. It was i n connection with this work that the author made an invest.igation of the chemical constituents of the pecan oil. A search of the literature revealed that the pecan has not been extensively investigated, although in recent years the nut has become of commercial importance. The carbohydrates of the pecan kernel have been studied by Friedman,4 and Deiler and Frapsb have recorded the constants of the oil making an estimate of fatty acids based on the observed iodine value. No record is given in Lewkowitsch of identified acids in the oil.
'S
EXPERIMENTAL The nuts used were of the Schley variety obtaiped from the Albany section in the State of Georgia. The shells were removed, and the kernels, which constitute about 60 per cent of the nut, were finely ground and subsequent)ly extracted with ether in a Soxhlet apparatus. The ethereal solution, upon evaporation and drying, yielded an oil representing 75 per cent of the weight of the kernel. The pecan oil has a light yellow color and a pleasant odor and taste. The characteristics are given in the following table :
...........
0.9118 Specific gravity 20°/200 C . . ~aponificationGalue.. . . . . . . . . . . . . . . . . . 191.5 0 . SO Acid value.. ........................... Iodine value (Habl).. . . . . . . . . . . . . . . . . . 9 7 . 1 20"/ZOo C ....................... 1.470
fi2~
HYDEOLYSI~ OF OIL In this investigation 50 grams of the extracted oil were used. This oil was first subjected to steam distillation, but only slight traces of acid came over. The oil was then cooled, sepwated from the water, and the latter extracted with ether to recover some suspended oil. The whole was then hydrolyzed by heating with an alcoholic solution of potassium hydroxide on a steam bath. The alcohol was largely removed by evaporation, the semisolid soaps were dissolved in water and extracted repeatedly with ether. The united ethereal solutions were washed thoroughly and dried with anhydrous sodium sulfate. After the ether had evaporated an impure yellow crystalline mass, about 0.1 gram, was obtained. This was washed with a small amount of alcohol and crystallized from alcohol, whereupon radiating, needle-like crystals (melt1
2 8
Received August 28, 1923. Schreiner and Skinner, J . A m . SOC.Agron., 10, 6 (1918). Skinner, Proc. Georgia-Florida Pecan Growers' Assoc., May 24, 1922,
p. 50. 4
c.
ing point, 134.0"C.) were obtained. When some of the substance was dissolved in chloroform containing a little acetic anhydride and a drop of sulfuric acid was added, a blue coloration was obtained, changing to green and finally to bkown. The habit, melting point, color reaction, and method of isolation show it to be a phytosterol.
FATTYACIDS The solution of potassium salts of the fatty acids which had been extracted with ether as described was acidified with sulfuric acid and the mixture distilled with steam. No volatile acids, however, were obtained. The fatty acids in the flask were taken up with ether; after washing and drying the ether was removed by means of a vacuum. A portion was heated under diminished pressure to remove all traces of ether before recording the constants. The acids, which were liquid a t room temperature, had the following values: Neutralization value. . . . . . . . . . . . . . . . . . . 196.7 Iodine value (Hiibl) . . . . . . . . . . . . . . . . . . . 1 0 0 . 6
In order to effect a separation of the saturated acids, the lead-salt-ether method, as modified by Baughman and Jamieson,6 was employed. The portion of acids which was insoluble in ether yielded 1.9 grams of solid acids melting a t 57" C.
-
ANALYSIS
0.1386 gram gave 0.3830 gram COa and 0.1587 gram HaO. C = 7 5 . 4 ; H 12.7 0.2073 gram neutralized 7.5 cc. 0.1 N KOH. Neutralization value = 202 9 CisHszOa requires C = 75.0 per cent; H = 12.5 per cent. Neutralization value = 219.1 CisHsaOa requires C = 76.1 per cent; H = 12.7 per cent. Neutralization value = 197.5
Fractional crystallization from alcohol was resorted to in order to accomplish a partial separation. Three fractions melting 66" to 67", 60" to G l " , and 57" to 58" C. were obtained; the first was small in amount. The melting point of the first fraction of the saturated acids indicates stearic acid. The acids melting at 60" to 61" C. and 57" to 58" C. crystallized in glistening tufts. The melting point and habit identify the second as palmitic acid. The last of these fractions would appear to be a mixture of the two acids, probably with a larger proportion of palmitic. The portion of lead salt which was soluble in ether was shaken with hydrochloric acid to convert it into the fatty acid. After washing and drying, the constants of the fatty acids were recorded: Specific gravity, 20°/200 C.. ........... 0.8962 Neutralization value.. . . . . . . . . . . . . . . . . . 197.1 Iodine value (Hubl) . . . . . . . . . . . . . . . . . . 105.4
The bromine addition derivatives of the unsaturated acids were then made and separated according to the method of Eibner and Muggenthaler.7 A 4-gram sample of the fatty acids was dissolved in dry ether, the mixture cooled to - 10" C., and bromine added very slowly. After standing for 2 hours a t -5" C. no crystals separated, thus indicating the absence of linolenic acid since linolenic hexabromide is insoluble in ether. The excess of bromine was then removed by washing with a solution of sodium thiosulfate, and after evaporating off the ether the bromine addition compounds Cotton Oil Press, 6, 41 (1922). Lewkowitsch, "Chemical Technology and Analysis of Oils, Fats and Waxes," Vol. I, 5th ed., p. 573. e
J . A m . Chem. Soc., 42, 11 (1920). Am., Chem. J . , 43, 90 (1910).
D.
7
January, 1924
INDUSTRIAL A N D ENGINEERING CHEiMISTRY
were dissolved in hot petroleum.ether and allowed to stand over night in the ice box. A white compound separated out and was filtered and washed with petroleum ether. The melting point was 114' C. This was evidently the tetrabromide of linolic acid. Ten grams of the unsaturated fatty acids were further examined by oxidation with a dilute solution of potassium permanganate by Hazura's method.8 The acids were converted into the potassium salt and an equal amount of potassium permanganate was added. The product of oxidation was digested with small amounts of ether to remove any unoxidized acids. It was then exhausted with large quantities of ether and the ethereal solution evaporated to small volume. A substance melting a t 127" to 128" C. separated. Upon
* Lewkowitsch, "Chemical Technology and Analysis OF
55
crystallizing from alcohol, glistening laminae separated, melting a t 130" C. ANALYSIS 0.1047 gram gave 0.2628 gram COa and 0.1093 gram HnO. H = 11.6. C1sHaaO4requires C = 68.4; H = 11.4
C = 68.5;
This is evidently dihydroxystearic acid, obtained on oxidation of oleic acid (melting point 136" C.). Using the iodine number of the unsaturated acid (105.4) and the theoretical values of oleic acid (90) and linolic acid (181.4), the percentages of acids in the unsaturated acid fraction were calpulated to be 83.3 per cent oleic and 16.8 per cent linolic. The composition of the oil is therefore approximately as follows:
Oils, Fats and
Waxes," Vol. I, 5th ed., p. 563,
. . . .. .. .. .. . . . . . . . . ........ g ~ ; ~ i ~ a ~] ; d Oleic acid, as glycerides.. . . Linolic acid, as glycerides.. . . .
Phytosterol (m. p . , 134' C , ) . . , ...
Per cent
80.0 16.0 4.0 Present
Influence of Water-Insoluble Matter w o n Polarization of Raw Cane Sugars' By G. H.Hardin N E W YORKS U G A R TRADELABORATORY, NEW YORK,N.
I
Y.
This table shows without N THE study of some of The water-insoluble matter content of a large number of raw cane explanation the relationthe more pressing probsugars is given. The average specific gravity of the water-insoluble ships of the various inlems pertaining to cane matter was found to be 1.87. The average percentage of watergredients tabulated. The sugar manufacture, cominsoluble matter of 96 degrees Cuban centrifugal sugar was found to majority of Cuban sugars paratively little attention be 0.159, the range extending from 0.017 to 0.423. The waterdo not contain sufficient has been paid to the presinsoluble matter consists of 87.5 per cent organic matter (cane fiber. ext,raneous substances to ence of extraneous subetc.) and 12.5 per cent mineral matter (earth. scale, lime salts, etc.). have an appreciable effect stances in raw sugars and The average error in polarization resulting from the presence of wateron the polarization, and it their effect on the polarizainsoluble matter is $0.021 sugar degree, the range extending from is only when percentages tion. While occurring in +0.001 to +0.057. I n the case of a sugar contaminated with of 0.2 and above are found relatively small amounts, 3.48 per cent sand, the error in polarization was found to be +0.35 that we may expect errors these substances should sugar degree. Owing to the high water-absorption capacity of cane of sufficient magnitude for neither be ignored nor confiber, a direct ratio is noted between moisture content of the sugars consideration. Much less sidered in any degree a and the insoluble constituents. interference is caused by negligible quality, but as a the inorganic matter, which factor of some importance in the fabrication and marketing of the raw commodity. has been reduced to almost a minimum in the improved Cuban raws contain varying amounts of bagacillo and foreign methods of manufacture. Consisting for the most part of matter, the latter consisting largely of minute particles of earth, lime particles, and iron rust and scale from the factory lime, scale, and earth. Since we are chiefly concerned with machinery, it constitutes a more or less stable factor in the the volumetric changes produced by these substances col- estimation of undissolved impurities, and apparently bears lectively, no attempt has been made to separate them further no well-defined relationship to other ingredients. Referring than dividing them into two general groups-viz., organic to the figures in the table, we find that 0.2 per cent of waterand inorganic matter. insoluble matter will cause an increase in volume of 0.028 Typical Cuban sugars, selected from samples received a t cc. for 26 grams of a sugar of 96 test. Bearing in mind that this laboratory, were used for examination and for ascertain- the divisions on the scale of the saccharimeter usually do not ing the effect of extraneous matter on polarization. The permit of a reading lower than 0.05 of a degree, the small settlings accumulated in the dissolved sugars were washed error might be assumed to be negligible; but taking the thoroughly with water by decantation, collected on filter premise that the small errors in sugar testing are largely addipaper, and dried. A weighed amount not exceeding 1 gram tive and that small differences are recorded in a general was taken for the determination of specific gravity. The average, no error of even 0.01 degree is too small to be igaverage specific gravity of the settlings from a number of nored. Not less significant from a commercial point of view different sugars was found to be 1.87. Results of the analyses is the fact that buyers and sellers of raw sugar employ averages of more than one hundred Cuban marks compiled by the t o the fourth decimal in settlement of their transactions. Roughly estimated, about 15 per cent of the Cuban raw laboratory when averaged gave 0.094 per cent of waterinsoluble matter, the percentages ranging from a minimum of sugars analyzed a t this laboratory contained on an average 0.017 to a maximum of 0.65 per cent. The figures of Table I of 0.25 per cent of water-insoluble matter, which, calculated arranged conveniently for quick comparisons will show the to volume in 26 grams, will give an increase in polarization proportion of inorganic to organic matter in the water-insolu- of 0.03 per cent. Furthermore, instances have been freble and the volume occupied by the latter in 26 grams of sugar. quently recorded of sugars running as high as 0.45 per cent in water-insoluble, but such sugars are not representative and 1 Presented before the Division of Sugar Chemistry at the 66th Meeting point to carelessness in manufacture. The effect on the polarof the American Chemical Society, Milwaukee, Wis.,September 10 to 14,1923.
