march, 1939 oil & soap reality our sub-neat to neat transi- tion, although it seems hardly like- ly that earlier workers failed to distinguish between melting to form liquid crystalline neat soap on the one hand and melting to form isotropic nigre on the other. Temperature (° C.) Heating 90 --72.0 95 --61.5 i00 --50.5 105 --38.5 110 --28.0 1t5 --t8.5 116 --16.0 117 --12.5 ACKNOWLEDGMENT i19 (+21.5 to -{-2,9.0) The authors are very heavily 120 45.0 122 50.5 indebted to Dr. A. S. Richardson 125 57.5 of this laboratory, under whose di- 130 67.5 132 73.5 rection the work was initiated and 134 81.0 135 86.0 carried out. His assistance is also gratefully acknowledged in the in- ~36 (90.0 to 101.0) terpretation and presentation of 14o the experimental results, upon 15215° which this paper is based, i56.5 i68,0 160 175.0 162 178.5 (1) Present address: Department of Chemistry, 164 Leland Stanford University. California. 165 (2) Bet. 43¢ 3120 (,1910) Vorliinder 166 (3) Bet, 32, 1598 (1899) Krafft 167 188.0 (4) Alexander's Coil. Chem. Vol, I, Chapter I68 (t90.5) by McBain (1926) I70 I72 208.0 (5) Z. physik Chem. A147, 92-110 (i930) 174 213.0 (6) J. Chem. Soc. p. 921 (1933) McBaln & I76 215.5 Field 177.5 (220.0 (7) International Critical Tables (t929) Vol. to 222.5) V. p. 449. 178 (8) A,S.C.Lawrence Trans. Farad. Soc. 34, 180 232.0 660, (1938). The figures given in Table 182 236.5 V refer to sodium palmitate monohydrate. 184 240.7 If the samples were prepared, as would be 185 inferred, by drying the soap to constant 186 245.0 weight at temperatures just above 100 ° C., 188 249.0 anhydrous soap would result. 190 253.5 (9) See Thiessen & Stauff. Z. phys. Chem. 192 257.0 A176. 397 (1936), (and previous papers). These authors believe that certain "geno- typical" transformations occur within the solid soan at temperatures weIi below 100 ° C. Our expermnce indicates that these changes are relatively small compared with the phase changes discussed herein. (10) J. Am. Chem. Soc, Sept. 1938 p. 2066 Void & Ferguson. Table I. Dilatometric Data for Sodium Palmitate. Reading* (ram.) Cooling (+1o.o to --8.5) +24.0 024.0 to 113.5) 125.5 136.0 156.o 159.5 178.5 183.0 (190.o to 186,0) (191.5) 199.5 204.5 (223) 228.5 232.5 243.0 Temperature Reading* i (° C.) (ram.) Heating Cooling 193 (292.0) 194.5 261.5 195 263.0 196 (265.0 to 269.0) t97 (30'7.0 315.5 to 309.0) 200 322.5 202 326.0 204 331.0 206 335.5 208 340.5 210 345.5 346.5 211 348.5 212 350.0 214 355.0 215 359.0 216 360.0 360.5 217 362.5 218 365.5 220 369.5 370,5 225 380.5 230 391.0 391.5 234.5 402.5 239.5 413.0 4t2.0 242 417.5 245 426.5 249 434.5 251 439.0 439.5 253 444.5 445.0 254.5 449.0' to (450.5) 255.5 459.0 459.5 257.5 464.0 464.0 261.5 474.0 266.5 488.5 272 5oi.5 501.5 277 515.5 282.5 530.0 286 54o.o 288 545.5 291,5 554.0 552.5 293.5 559.5 558.5 294.5 562.0 295.5 570.5 297 574.0 299 580.0 580.5 304.5 593.5 The diiatometer readings represent the dis- tance of the mercury menis~:us from a fixed reference point. These readings are directly proportional to the volume of the soap and could be converted to a volume basis by using capillary calibration, and corrections for the mercury, the dilatomer volume, etc, ( ) represents points in a state of adjustment to the stable equilibrium curve. LECITHIN-Its Manufacture and Use in the Fat and 0il Industry Abstract By J. EICHBERG AMERICAN LECITHIN CO., INC., ELMHURST, L. I., NEW YORK Lecithin, produced economically and on a commercial sc~Ae from soybeans, has been on the market in this country only since 1929. The lecithin and associated phosphatides are extracted with a petroleum solvent and separated mechanically from the rfiass of oil, Special grades may be prepared by subjecting to further solvent purification and fractional crystalizatlon. In the fat and oil industry the properties of lecithin are used to inhibit rancidification and to modify interracial tension relationships. Quantities used range from .01% to 1.0%. Various applicatlons are noted as in oleomargar- ine, shortenings, confections, coatings and ic- irtgs, vitamin oils and for industrial purposes. W HILE lecithin was first prepared many years ago from egg yolk and brain substance, its development from a laboratory curiosity and costly pharmaceutical into an industrially useful commodity, available in quantity, is of recent date. And this *ransition waited upon recognition of the natural connection between lecithin and the production of edible oils 1, for essentially lecithin is a close relative of ordinary oils and fats. Indeed, lecithin is a tri-glv- ceride except for substitution of one of the fatty acid radicals by phosphoric acid combined with a nitrogen containing basel For years the term "lecithin" was used inclusively. The broader term is "phosphatide" and from a strict- ly technical standpoint lecithin is that alcohol soluble phosphatide containing the base choline. How- ever, commercial lecithins have al- ways consisted of mixtures of phosphatides a, especially lecithin and cephalin (alcohol insoluble, with amino-ethyl alcohol as the base) along with a carrier of oil and are still generally referred to in the trade as "lecithin." The com- mercial product may or may not contain an appreciable proportion of carbohydrate. The fatty acid radicals vary depending, for ex- ample, on the species of bean and the environment so that phos- phatides from American grown beans will differ slightly from those of Manchurian origin. There is always one unsaturated fatty acid radical, however, which appears to 51
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`oil & soap march, 1939 play a major physiological role. It follows that in analytical work the factor of 26 x P, used to cal- culate the purity of egg lecithin, should be applied relatively rather than literally to commercial veg- etable lecithin. An analysis of oil- free soybean phosphatide, gave 3.1 total phosphorus, indicating a high- er factor. However, egg lecithin as produced is often a mixture and not a pure chemical entity and even very highly purified egg lecithin may exhibit a tendency to become in part alcohol insoluble. For con- venience the term "Lecithin" here- inafter refers to the soya-lecithin of commerce unless qualified by the context. Depending upon the raw mate- rial and method of manufacture the free fatty acid content of leci- thin products will vary but, to avoid an excessively high figure in any case, should not be determined by direct titration in the usual way. "INe lecithin and other phosphatides tend to react with the alkali. Be- sides saponifying more readily than ordinary oils and fats, lecithin con- tains a free acid hydroxyl in the phosphoric acid group~; cephalin in particular has somewhat of an "organic acid" character and is isoelectric at a pH of about 5. The free fatty acid should be run on the matter extracted by washing with an excess of cold acetone. Preliminary addition of a small amount of ether facilitates this operation; the acetone may be mixed in warm but the whole mass should be chilled to -15 ° C. Probably the first to envisage the possibility of producing vegetable lecithin commercially from soy- beans and to devise feasible proc- esses and equipment was Hermann Bollmann of Hamburg. Bollmann concerned himself with solvent extraction. After the war soy- beans were handled increasingly by the German oil mills and being relatively rich in lecithin afforded an excellent source for this sub- stance. Bollmann originally used a combined solvent of about two parts alcohol and three parts ben- zol or a volatile liquid hydrocarbon on the theory that the residual meal would be more palatable 5. Also this combined solvent gave a larger lecithin yield by loosening or breaking the lecithin-protein com- bination in the bean. The current of solvent moved counter to the direction of bean travel and a simi- lar counter-current principle was employed in steaming the meal to remove traces of solvent 6. Conway and his associates in this country as early as 1923 appre- ciated the possibilities of solvent extraction including lecithin re- covery, and negotiated with Boll- mann for licenses under the latter's American patents. A pioneer plant was put under construction in Nor- folk but for various reasons the project did not progress to regular commercial operation. This enter- prise, however, gave impetus to the introduction of soya-lecithin as well as stimulated interest in the extrac- tion of oil seeds. Since that time the domestic supply of soybeans has grown tremendously, centering in Illinois, and the past five years have seen solvent extraction be- come a large scale reality. Boll- mann's methods for separation and purification of lecithin as an inte- gral part of the extraction process are being successfully applied here as in Europe. Today, a single sol- vent derived from petroleum seems to be preferred to Bollmann's com- bined solvenff. Soybeans contain about 1½% to 3% of phosphatide but not all is removed during ex- traction so that the meal retains about 1%. While the single sol- vent does not afford as large a yield the refined lecithins are much freer from carbohydrates. Before passing through the sol- vent the beans are cleaned, dried and flaked. The oil and lecithin dissolve out and after evaporation of the solvent moisture is intro- duced to hydrate the lecithin. It is then possible to effect a good sepa- ration with high speed centrifugals. The operation is continuous. A small proportion of oil remains "bound" to the lecithin, amounting to about 30% of the weight of the lecithin, and this later serves as a carrier. The lecithin emulsion is sub- jected to vacuum distillation to drive off the water and this treat- ment also improves the taste and odor s . For certain purposes light colored grades are desired and bleaching with peroxides, for ex- ample hydrogen peroxide, effects a substantial reduction in the degree of red and yellow coloration 9, The temperatures applied during proc- essing do not prove injurious due to the protective presence of the oil and moisture. The carrier of soya oil in the finished lecithin guards against change of the active substance, which it renders soft and convenient to use. Purified lecithin, free from oil, is waxy and gummy and less solu- ble. The demand for this type comes chiefly from the pharmaceu- tical trade. The production cost is high. Less costly but still more expensive than the straight soya- lecithin are those grades which can be made by substituting some other oil or fat for soya oil as the carrier. For use in pure chocolate coatings, a purified grade with a cocoabutter carrier most fully answers trade requirements. The soya-lecithin after bleaching is washed with a selective solvent, usually acetone, in which the oil dissolves but the lecithin does not. The supernatant liquid is drawn off and the specified carrier, such as hydrogenated short- tening or refined cocoanut whole oil, is mixed in. The residual sol- vent can then be evaporated 1°. Commercial soya-lecithin can be split up into several closely related components by treating with alco- hol, separating the residue insolu- ble at about 60 ° C. and subjecting the solution to fractional crystalli- zation by cooling n. So far no im- portant commercial advantage or superiority has been found for any of the phosphatide fractions com- pared to the soya-lecithin obtained by the above described process which would justify the cost of separation. While it has been re- ported that highly purified cephalin is a more effective anti-oxidant than highly purified lecithin 12, it should be borne in mind that we are dealing with a natural extract, obtained by mechanical rather than chemical means. Indeed, for most purposes the natural lecithin-oil complex seems superior to the separated fractions and to a con- siderable extent the process of iso- lation may denature or change the original potency, even if the com- ponents should be later mixed back together in the same proportions. Nevertheless, future research will probably include a more detailed study of the individual vegetable phosphatides as well as of stable lecithin-protein combinations which might be used in acid media, as in mayonnaiselS, 14 As early as 1924 Bollmann pointed out that ordinary refining and deodorizing methods destroy the lecithin naturally present m oils from seeds and that the addi- tion of small fractions of a percent of lecithin to refined oils retards rancidity 1~. He observed too that in frying the oil did not squirt or spatter in the usual way. Lecithin is now widely used in various vege- table and animal oils and shorten- 52
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`march, 1939 oil & soap ings to inhibit oxidation and ran- cidity, in quantities up to 0.15%. Continued use by the trade as well as many accelerated tests have shown its value as an anti-oxidant, and as would be expected the most striking results are obtained with the more unsaturated oils and fats. Beyond 0,15% the improvement is not proportionate and in some cases from 0.05% to 0.1% has been adequate~6, ~7. It is interesting to note that in cod liver and halibut liver oiI preparations vitamin po- tency is being prolonged by incor- poration of soya-lecithin ~s. Besides counteracting rancidity (and retarding hydrolysis TM) leci- thin, because of its colloidal effects, can be advantageously used in mix- tures of different melting point fat- ty oils such as exemplified by com- pound shortenings ~°, or in fats con- taining glyceride components of different melting points such as coconut oiI products or cocoabutter. The lecithin, pre-mixed with part of the melted oils, should be added iust prior to chilling. Lecithinated shortening exhibits greater physical stability, being less subject to "sep- aration," "streaking" and "granu- lation." The fact that the mass of plasticized shortening is better adapted to bind the bubbles of air is evidenced indirectly by the foam- ing which occurs while testing in the Swift Stability Apparatus. On the other hand, the interracial tension relative to water is reduced as indicated by smaller droplets when slices of potatoes are deep fried 2~. Shortenings containing about 0.05% or more of lecithin darken very considerably during deep fry- ing or on heating to elevated tem- peratures 22. This may be ascribed to carbohydrate and perhaps indi- rectly to the phosphoric acid group in the lecithin molecule. Strangely enough with some compounds tested, but not all, the addition of 0.01'% of lecithin resulted in a slightly lower Lovibond reading initially and did not increase the coloration after heating to 200 ° C. and frying potatoes. The control sample emitted a more pungent odor and during frying the bubbles were larger and less uniform. It is known, of course, that lecithin reduces interracial tension between oils and veater ~3. Evidently the composition of the compound and the character of its oils and fats determines the maximum amount of lecithin which can be used where deep frying is a factor, so that a series of tests should be made for each formula. Just as lecithin inhibits granula- tion so does it retard crystalliza- tion of stearine from refined cot- tonseed oil at lower temperatures 24. An analagous effect has been noted in the setting of eocoabutter at temperatures where some of the lower melting point fractions re- main liquid2L An effort was made to utilize the action of lecithin on surface tension to facilitate the pressing of oils, as with cocoabutter from chocolate liquor, but this has not yet proven significant 26. Adding 0.5% to 2% of lecithin to shortening substantially increases the lubricating properties (shorten- ing value) and emulsifiability 27,.2s Such a shortening would be m- tended for bakery use exclusively, in bread or cakes or biscuits and crackers. The lecithin causes the shortening to spread more readily throughout the dough and promotes uniformity and better moisture re- tention as well as increases tender- ness. Instead of blending the leci- thin directly with the shortening it may be first emulsified with water and then mixed with the fat but this should preferably be done shortly before use ~9. In any event, to assure optimum results the bak- ery formula should be kept proper- ly balanced. Lecithin forms perfectly homo- geneous milky emulsions with wa- ter which may be diluted almost indefinitely. One of the first uses for soya-Iecithin was in oleomar- garine Where it replaced more ex- pensive egg yolk added to improve the frying properties 3°. Up to 0.30% of lecithin incorporated at any stage, usually in the churn, counteracts spattering and the sticking of milk solids in the frying pan and imparts desirable foaming and browing effects. At the same time there is some increase in spreadability and shortening value. Thus, with lecithin oleomargarine is a more universal household fat, for kitchen as well as table use. Butter, of course, contains a frac- tional percentage of lecithin derived from the milk TM $2; favorable re- sults have been reported with proc- ess or renovated butter. Oleo- margarine and butter are emulsions containing much more fat than water. Several examples of the other type where water is the con- tinuous phase may be given. In a 3% emulsion of oleo resin of cap- sicum 0.50% of lecithin was satis- factorily used as the emulsifying agent, while with a 50% castor oil or cod liver oil emulsion 4% to 5% of lecithin was used in a prepara- tion stable for months. Cake fillings and icings compris- ing shortening and water cream up to larger volume when lecithin is used. The moisture is more finely divided and uniformly dis- tributed and the texture apprecia- bly smoother ~3. Likewise fhe sur- face of icings finishes with a more attractive lustre. "Lecithinated" fats for pan or slab greasing are more spreadable and go further. Another instance of lecithin util- ity where fats must be emulsified in the presence of moisture may be seen in the manufacture of con- fectionery, especially chewing can- dies, such as caramels. Ordinarily the added fat floats on top during the cook and the candy itself tends to be greasy to the touch, the film of fat being readily oxidizable. A fractional percentage of lecithin causes the fat to disappear and mix throughout the batch during cook- ing and improves the handling and keeping properties of the caramel. Moreover, the caramel cuts better and cleaner due to the greater lub- ricating value of the fatS% Leci- thin can be used to similar advan- tage in boiled icings, such as butter- scotch. Having an affinity for both oil and water and being adsorbed at interfaces, lecithin promotes the rapid and complete wetting by oils or fats of a wide variety of solid particles. This property, plus the fact that the oil will form a thin- ner continuous film, makes lecithin a time, labor and material saver. Thus, where plastic cocoanut butter or shortening is to be mixed with sugar to form a wafer filling, leci- thin permits a higher solids content while maintaining the necessary workability; the mass has a better body and the fat is less likely to bleed from the sugar. So too in coatings where oil or fat is the liquid phase lecithin facilitates grinding and uniform dispersion and improves the flow and covering propertiesSL The first 0.10% shows the greatest effect and with in- creasmg additions the viscosity curve flattens out, depending on the physical properties of the solid and the proportion of free liquid. It may be noted that when mixed with oils as with water, lecithin gives a colloidal solution. However, while lecithin wilt form a stable emulsion or dispersion with water in any proportion, only relatively 53
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`oil & soap march, 1939 small amounts can be dissolved in oils and fats. Its solubility is, of course, greater at high tempera- tures. The addition of lecithin does not reduce the viscosity of a fatty oil per se, the tendency is rather the reverse. Lecithin finds many miscellane- ous applications with oil and fat products. A small percentage in- corporated in citrus oils and other oil soluble flavors acts as a fixative, reducing flavor losses due to volatil- ization, and at the same time as- sures better flavor distribution, particularly in the presence of moisturea% Cosmetics, including shaving creams, made with lecithin possesses enhanced softening and penetrating value 37, 38. Liquid soaps so treated are milder and more thorough in cleansing action 39, 40 Peculiarly enough lecithin, which forms milky emulsions with water, gives a clear solution with liquid soap. Still other uses in conjunc- tion with oily materials are in the drumming or fat liquoring of leath- ers 41 and in the sizing of textile materials 42. The addition of about 15% benzyl alcohol to the lecithin has been found helpful in making water enmlsions without undue stir- ring4L Hardly ten years have elapsed since lecithin became available com- mercially and was introduced to industry. In that period a variety of uses have been developed and factories built in the United States which are currently producing all that can be sold, with considerable capacity to spare. As consumption has mounted, the price trend has been downward to about 1/3 of the 1929 level. This is simply an ex- pression of the normal relationship between the cost of producing and selling as the numerator and the tonnage as the denominator. Many patents on methods of manufac- ture and use have encouraged mis- sionary work in this field and made possible enlisting the interest and capital necessary for research and for plant equipment. The recovery of lecithin has increased the value of farm products and provided a new and useful material; its future depends more on expanding exist- ing markets and discovering new uses than on solving manufacturing or technological problems. 1. Rewald -- Pharm. Zeitung, No. 88, 1928. 2. MacLean -- Lecithin and Allied Sub- stances, p. 6. 3. Leyene -- Jour. Biol, Chem. p. 759, Jan. 1925. 4. Mathews -- Physlological Chemistry, p, 108. 5. U. S. Patent N,o. 1464557, 6. U. S. Patent No. 1371546. 7. U. S. Patent No. 2024398. 8. U. S. Patent No. 1776720. 9- U. S. Patent No. 1893393. 10. U. S. Patent No. 1895424. 11. U. S. Patent No. 1667767. 12. Olcott & Mattill -- Oil & Soap 13 (4) p. 100, ,1936. 13. Olsen -- Ind. & Eng, Chem,, Vol. 27, D. 1222, Oct. 1935. 14. g$~hitaker -- Jour. Dairy Science, Vol. XIII, No. I. 15. U. S. Patent No. 1575529. 16, Royce -- Soap, p, 25, Sept. 1931. 17. Evans -- Ind. & Eng. Chem., p. 329, Mar. 1935. 18. Holmes -- Ind. & Eng. Chem., p. 133, lan. 1936. 19. Trusler -- Oil & Fat Ind., April 1931. 20. U. S. Patent No. 1831728. 21. Oil & Soap, p. 261, Oct. 1936. 22. U. S. Patent No. 1982186. 23. Drug & Cosmetic Ind., May 1932. 24. U. S. Patent No. 2050528. 25. Manf. Confectioner, Nov. 1929'. 26. U. S. Patent No. 1903397. 27. Bakers Review, April .1931. 28. Siebel Tech. Review, Jan. 1931. 29. U. S. Patent No. 1936718 30. German Patent No. 142397. 3l. Horrall, Purdue Univ., Bul. 401. 32. Fleming -- Anal. Ed, Ind. & Eng. Chem., Vol. 4, p. 362, Oct. 15, 1932. 33. Glabau -- Bakers Weekly, Nov. 29, 1930. 34. U. S. Patent No. 1859240. 35. U. S. Patent No. 1781672 36. U. S. Patent No. 2019494. 37. Augustin -- Amer. Perfumer, Sept. 1932. 38. MacDougall -- Proc, Am. Philo. Soc., p. 33, Vol. LXVII, 39. Soap, p. 55, June 1933. 40. Seifensmder -- Zeit., Nr. 5I, Dec. 1933. 41. U, S. Patent No. 1779012. 42. U. S. Patent No. I946332. 43. U. S. Patent No. 1934005. lVinterizing Coolers A MODERN OIL REFINERY Tank Farm and filling equipment A. E. Staley & Company Decatur, Illinois Deodorizers 54 Bleaching Presses Exterior Oil Refinery Centri[uges
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