SOYBEAN OIL in the Food Industry M. M. DURKEE A. E. Btaley Manufacturing Company, Decatur, Ill.
COlkTtPSy,
irig wine other oil seeds, such as linseed or cottonseed. The lreans are ground or Aaked, dried to a moisture content of 3 to -1 per cent, heated and tempered in a cooker, then formed into a cake before pressing. Much hand labor is required, and the irocess is not continuous. I n Europe, solvent extraction is the preferred method. In fact', t h e largest soybean plant in the world, handling over -10,000 bushels per day, uses this process. From all information available this is operated as a Continuous method, I n (iur own country disastrous explosions have retarded the de\-elopment of solvent extraction. Extraction is the logical iiiethod and the one that undoubtedly will eventually be adopted, since it should be possible to overcome the explosion hazard. There is, a t present, a prejudice against the low-oil meal resulting from this process, possibly with some justification, but this may be overcome by a widespread selling program or technical improvement, or both. The continuous high-pressure process by means of expellers i* the method most widely used in this country. Properly cleaned beans are ground, dried to a low moisture content, and while hot are conreyed to expellers. I n these machines, by means: of a heavy shaft carrying discontinuous spiral projections, a pressure of 5 to 10 tons per square inch is set up in a strong slotted cage. The bars forming the cage are spaced only a few t'housandths of an inch apart. Under the high temperature and pressure the protein cell structure of the bean becomes plast,ic, the oil is pressed out and drains through the narrow dots between the bars of the expeller barrel, while the solid portion of the beans discharges past the exit jaws around the shaft in a thin cake. The meal made from the cake has a protein cont'ent of about 42 per cent, and is said to be the only protein concentrat'efrom a vegetable source capable of supplying all the protein needs of animals. The crude soybean oil is *trained in a rotary strainer to remove particles of meal and i- then filtered.
Herald-Reizeu', Decatur, I11
ESDLESSS C R E W RATE
OF
C o N V E Y o R S F O R MOVING THE BEASS .4T THE 10,000 BUSHELS.I DAY FROM O N E PROCESS TO ANOTHER IIC THE PLANT
OR fifteen years there has been an aatoiiicliing growth in the acreage devoted to soybeans by the farmers of the Middlewest. Originally introduced a. a curiosity in 1804 and grown as such in Sort11 Carolina during the last century, the culture of the soybean is ~ O T Ttaking its place as one of the smaller major crops of our country. Only 50,000 acres were planted in the United States in 190i; by 1924 this had jumped to 2,500,000, and in 1935 more t'han 5,000,000 acres were planted. In 1934, 18,627,000 lxishels were harvested, in 1935,39,637,000bushels, and it is reasonable to suppose that a further increase will take place this year now that the niidweet,ern farmer has becoiiie convinced of the merits of thi. crop. Industry has been faced with the challenge of developing a technology for making use of soybeans! adapt'ing the methods, and meeting the needs of this country.
Composition
Pressing
111 crude oil the free fatty acids present usually range around 0.5 per cent, indicating considerable natural protection against hydrolysis in sound beans. It should contain less than 0.1 per cent of moisture and volatile matter: it has a rather dark color, reading about 120 yellon- and 22 red on the Lovibond coloriiiieter. The crilor of this oil is peculiar and will be dis-
T h e e method. are iii general lice for separating oil froiii the bean: expelling, hydraulic pre:*iiig, and solvent extraction. The oldest method for remoi-ing the oil utilized the aiicient wedge press of 3Ianchuria. It-. modern counterpart is the hydraulic pre.5, no^ u*ed in Anierica hy iiiills formerly crush-
Symposium on the Chemistry I
Presented before the Division of .agricultural and Food Chemistry a t the 9 l s t Meeting
898
vussed later. Expeller oil holds 1 to 2 per cent of phosphatides, a portion of which deposits on standing; or, when the oil is deitined for the paint trade, thiq niaterial can be removed entirely by any one of several methods. Baughman and Jainiesori ( 2 ) carefully determined the chemical composition of the oil obtained by the expeller process from the Mammoth Yellow variety. The following rehults were obtained: Glycerides Linolenic Linoleic Oleic Palmitic
% 2.3
51.5 33.4 6.8
Glycerides Stearic Arachidic Lignoceric Unsaponifiable
For food purposes the crude soybean oil is refined in five main steps. The fresh, refined oil is sweet, has a low fatty acid content, and can be made almost water-white. A dark type of soybean oil found an early market in the manufacture of oleomargarine since it imparted a butter-like color to the finished product. A considerable volume of refined soybean oil is marketed as a salad or cooking oil, and large quantities are used in the manufacture of vegetable shortenings, blended with cottonseed or other oils. Refined soybean oil has a greater degree of stability against development of rancidity due to oxidation than most food oils, which, in view of its high percentage of unsaturated acids, shows that it must contain some natural inhibitor which is resistant to the refining process. The development of a reversion flavor in this oil is evidently not the same type of reaction as that ordinarily causing rancidity ; the prevention of this development is a major problem. When it is solved, refined soybean oil will take its place among American food oils on a par with corn and cottonseed oils.
% 4.4 0.i 0.1 0.6
Searly 90 per cent of the fatty acids present is unsaturated, placing the oil in the drying class. The iodine number of domestic oil produced from mixed mill-type beans is about 134. A study of Russian soybean oils by Yushkevich (9) from seeds grown under a wide range of climatic conditions shows a fairly constant linoleic acid content of around 50 per cent, but the more highly unsaturated linolenic glyceride varied from 0.46 to 12.49 per cent. The author is not aware of any comprehensive study on soybeans grown in this country under varying climatic conditions, but some work has been done on the composition of different varieties. I n the trade the impression exists t h a t black beans are not as suitable as a source of oil for edible use as for paints. Japanese chemists have reported that crude soybean oil contains vitamin E, though there is some evidence that their results may have been due to the linoleic acid, a point to he discussed later. Tests and a report by a private laboratory in 1933 concerning vitamin X in this oil were as follows: “Crude soybean oil has 9.5 mg. per pound of carotene but in the refining process more than 95 per cent is destroyed I n bringing the potency of the refined oil back to that of the original crude, 4.5 grams of crystallized carotene per 500 pounds of oil would be required.” The opinion was based on optical tests and not on the more reliable feeding experiments.
Refining
ing 111 regard to flavor and not a- accustomed to the use of oil in the home as are the peoples of Europe. Application of the corn-oil refining and deodorizing methods of eight years ago gave results t h a t were surprisingly good; the soy oil waq remarkably low in color, contained less than 0.015 per cent free fatty acid, and was sweet and bland, but on storage in bulk or in retail packages the story was quite different. After a few weeks a so-called “reversion” took place and the oil acquired a flavor described as “grassy” or “beany.” Though this oil from domestic beans was much better than the oil refined from Manchurian crudeh, it still suffered in comparison with other salad oils. During the years following the first refining trials with domestic oil, the details of the general method have been altered to secure a more stable finished oil. Five main steps are required : neutralization, washing, bleaching, winterization, and deodorizing treatments. The neutralization of the crude oil is carried out by means of alkali treatment in large open tanks equipped with a stirring device, heating coils, sprays for the alkaline solutions, and usually a jacketed settling cone. These neutralizing tanks
Though drying oils have been considered unsuited for human consumption, soybean oil has proved a surprising exception to the rule. During the after-the-war shortage of both drying and nondrying oils, great quantities of Manchurian soybean oil were imported-336,825,000 pounds in 1918. Considerable Manchurian oil was refined during this period by methods then in use for treating crude cottonseed oil. Results were disappointing in t h a t t h e purified oil often had a distinct “fishy” or “painty” taste. Only the great shortage of oils made i t acceptable in the food industry. The oil acquired a bad reputation when i t was compared with refined cottonseed, corn, or peanut oilq then on the market but, even so, the cottonseed oil acceptable at t h a t time would hardly pass muster today in comparison with the high standard of purity now required. In 1928 American inanufacturers felt that it should be possible to make a satisfactory food oil from the domestic beans. Tremendous quantities of the Manchurian product hape been used in European countries for edible purpose*, though i t must be admitted that the American public is more discriminat-
and Technology of Soybeans of the dmerican Chemical Society, Kansas City, M o . , April 13 t o 17, 1936.
899
I 1
SOYBEAN EXPELLERS
are called "refining kettles." The oil a t a temperature of about 70" F. is emulsified with caustic soda solution varying from 10" to 14" B6. in slight excess over the amount required to neutralize the free fatty acids. The emulsion is the waterin-oil'type; care must be used to prevent a reversal to an oilin-water mixture. Heating is carried on with moderate stirring until the so-called break appears; this break consists of small clots of soap formed from the free fatty acid originally present, together with any excess lye, and nearly all the lipoids or other impurities present. Under continued heat and slow stirring the clots grow larger and a t the right temperature are sufficiently fluid to coalesce if allowed to settle. At this point the heat is shut off the final temperature seldom reading 160" F., and the stirring is stopped, allowing the impurities to settle as "soap stock" underneath the neutralized oil. Much depends on the skill of the refiner and, since there are many variables, no two batches can be handled in exactly the same manner. After settling for 18 or 20 hours in the refining kettle, the clear supernatant oil is drawn off, leaving the soap stock as a by-product for the manufacture of distilled fatty acids. Much edible oil is now neutralized by a continuous method. In this process the neutralizing time is very short, being carried out in a small beater, followed by a high-speed centrifugal separation of the neutral oil from the soap stock. Soybean oil coming from the neutralizing kettles or centrifuge should be entirely free from lipoids, as shown by the "heat-break" test, which consists of freedom from any floc when a small sample of the oil is heated to 600" F. The neutralized oil is then washed by stirring with a t least 8 or 10 per cent of the purest water available, heating nearly to the boiling point, and again allowing to settle. The water should be free from calcium or magnesium salts; otherwise, traces of alkaline earth soaps may cause flavor difficulties later. Bleaching is the third step. The wet oil is dried and stirred under a vacuum with fuller's earth, activated carbon, and other adsorptive agents, depending on results obtained by laboratory tests. Ordinarily only a small percentage of bleaching mixture is used, and temperatures seldom exceed 230" F.
Soybean oil, when pure, is a natural winter oil t h a t remains clear for an indefinite period when kept a t 32" F. Actually, commercial oil in bulk begins to freeze a t 25' F. melting a t 27", so that it would seem unnecessary to winter-press the oil. However, small quantities of unknown substances (not stearines but quite possibly sterols) are removed by cold filtration. Following a winter-pressing treatment, the final step (called "deodorization") is carried out. This is perhaps the most important procedure of all, but its success or failure depends on the purity of the oil available up to this point. The theory of deodorization is simple; i t is merely a vacuum steam distillation to remove the odorous substances from the oil. As is often the case, actual practice requires costly equipment. Unusually high vacuums are now employed, especially considering the size of the deodorizing tanks; often the internal pressure is less than 5 mm. of mercury even when there is a heavy flow of superheated steam through the hot oil. Deodorization is carried on for many hours, under conditions of temperature, rate of flow, temperature of steam, and vacuum that past experience dictates as best for the particular oil under treatment. Finally the oil is cooled under a high vacuum and is ready for the food industry. Properly prepared, the freshly refined oil is sweet and has perhaps a slight "grassy" odor if heated to about 425" F. in a glass beaker, far above the range of deep fat frying. The Lovibond tintometer shows a color of around 10 to 15 yellow and 1 to 1.5 red for ordinary light colored bleached oil. An especially light oil can be made which is nearly water-white. The free fatty acid content is less than 0.02 per cent, sometimes less than 0.01 per cent.
Trade Channels Much domestic edible oil is utilized in mayonnaise and salad dressings, but no statistics are available. I n most cases a mayonnaise maker uses the oil in the form of a blend with cottonseed or corn oil, lowering the average cost of the whole salad-oil mixture. There have been times when domestic soybean oil has been considerably cheaper to produce than other edible oils and so buyers for certain food uses have had an incentive to experiment, for even qlight differences in price 900
AUGUST, 1936
INDUSTRIAL AND ENGINEERING CHEMISTRY
hold a powerful attraction to quantity users. The versatility of soybean oil, in t h a t i t can be used both for edible and technical purposes, swings its consumption to the outlet ruling highest in price. For the past two years the price level of drying oils has ruled under that for food oils, so that now about 80 per cent of all soybean oil reaches the food industry. Students of world conditions seem to think that drying oils may be cheaper than those classed as edible for perhaps a year or two. It is important, then, that this oil be still further improved to fit the needs of the edible trade.
Special Type of Soybean Oil
90 1
type of oil needed; some use oiily a few per cent, others as high as 25 per cent of the total oil.
Salad Oil Bleached, highly refined soy oil has found a market in large industrial centers where a demand exists for a salad oil cheaper than other edible oils, and where the tendency to slight flavor reversion is not an especially objectionable feature. A few enterprising canners have sold large quantities of canned oil by filling and moving fresh oil rapidly into consuming channels; the foreign population in large industrial centers, accustomed to oil dressings and deep-fat frying with poor grades of olive oil, are not averse to the slight characteristic flavor of light colored soybean oil. The sale of the soybean salad oil is spreading to a general class of trade, especially a t times when the price is attractive.
Margarine colored to resemble butter is taxed prohibitively. A few enterprising margarine manufacturers discovered that they could make colored margarine by using a naturally dark refined oil and thus escape the heavy tax on a n artificially colored product. Experiments with corn oil led to Margarines a product giving a very dark oil, but margarine made from it had an unsatisfactory brownish tinge. However, a dark soyEdible soybean oil is again becoming an important factor bean oil was developed which gave remarkably good results in the margarine industry now that butter prices are higher. and sold a t a premium over all other vegetable oils to margaAccording to figures as reported by margarine manufacturers rine manufacturers. I n brief, the impurities were removed to the Bureau of Internal Revenue, the actual margarine profrom soybean oil with a minimum destruction of color. duction for 1934 was 264,359,424 pounds, and for 1935, Strangely enough, though the resulting oil carried a slight 381,591,558 pounds. During 1934 only 24,413 pounds of s o y amount of residual bean flavor, so much of the reversion-prebean oil were used, whereas in 1938 the volume of soybean oil venting substances were retained that the butter-type soyused in the manufacture of margarines totaled 1,739,687 bean oil was remarkably stable. The color of this soybean pounds. I n other words, while the volume of margarine inoil is peculiar in that a moderate amount of the dark type in a creased 44 per cent last year over the year before, the increase margarine seems to have considerable tinctorial power. for soybean oil in margarine was over 7000 per cent. PresumThere is a simple spot plate test to demonstrate this: Select a ably most of the soybean oil now used in margarine is partially sample of dark refined cottonseed or corn oil with nearly the hydrogenated to a plastic state just as is the case with cottonsame color as a sample of a dark refined soybean oil, as measseed oil. Xot many years ago it would have been thought ured by the usual color comparison in a Lovibond tintometer. nearly impossible to make an all-vegetable margarine without Place a few drops of each u&g coconutoil, but today s i d e b y s i d e on a white excellent table spreads are porcelain spot plate. The sold with h y d r o g e n a t e d dark corn or c o t t o n s e e d vegetable oils exclusively as oils will show a pale color the base. in a thin layer, whereas the Vegetable Shortendark t y p e of s o y b e a n oil ings will show a brilliant yellow color reflection. A margaThe m a n u f a c t u r e r s of rine produced from such vegetable shortenings have oil has sufficient color to become heavy consumers simulate butter in appearof hydrogenated soybean ance. for lard compound. The D u r i n g 1930 and 1931 Bureau of the Census reconsiderable s p e cia 1 dark ports a c o n s u m p t i o n of soybean oil was used in the 489,000 pounds in 1933 and m a r g a r i n e trade, finally 2,735,000 in 1934. Accuopening the way for the use rate f i g u r e s for 1935 are of dark refined palm oil. now available and show a From the s t a n d p o i n t of twenty f o l d i n c r e a s e as color and consistency the compared t80 1934. It is latter is better suited for the opinion of manufacmargarine than ,is soybean turers that 10 to 15 per cent oil. S o o n t h e l a w w a s of hydrogenated soybean oil amended to include natucan be blended with cottonrally colored m a r g a r i n e seed oil without difficulty. under the tax provision, and One maker states that soysoybean oil lost this outlet. bean oil can best be used in If a moderate amount of a shortening by hardening this special dark edible soyit to the rather high titer of bean oil is used in mayon51" C. before blending with naise, i t has the effect of cottonseed oil. I n other brightening and improving words, the soybean-oil porthe appearance of the prodtion should be highly satuuct. Makers differ in the rated before being used in a Courtesy, Herald-Review, Decatur, Ill. proportion of this special FORMING P E L L E T S O F SOYBEAN k'lE.4.L FOR CATTLE FEED blend. Another large con-
INDUSTRIAL AND ENGINEERING CHEMISTRY
902
HIGH-~~CU DEODORIZER UM COOLER
miner of hydrogenated soybean oil finds t h a t it improve. the texture of lard compound. H e expects to continue it. use regardlesi of a n y reasonable price increase. It is evident t h a t domeqtic soybean oil is finding a place here and there in the food induqtry; but u p to the preqent time price appeal ha; been the entering wedge. It ha. sold from 1 to 2 cents per pound under cottonseed oil-in other words, at a point where the savings involved ha\-e overbalanced the fear of possible troubles from a rever-ion in flavor. Lately the demand from the food industry has brought the price differential closer. T h k indicates that less iniportance is being attached to the poAbility of flavor revertion, which would ieem to indicate t h a t some of the fear i- being overcome.
Reversion Domedic refined soybean oil can be prepared nearly as sweet and bland as any other edible oil, but the difficulty is to keep i t t h a t way. After a yariable period, usually from a few weeks t’o a few months, the oil often acquires a slight’ peculiar “grassy” or “paint,-like” flavor. But this is not true reversion in t h a t the newly developed flavor does not suggest undeodorized oil. The lat,ter has a characteristic and pronounced odor and flavor thought to be due to methyl-n-nonyl ketone. If i t were not for this tendency, soybean oil would be on an equal footing with cottonseed. corn, or other salad oils. This so-called reversion has been thought’ to be due t’o oxidation, hut this theory has been disproved. The stability of oils against rancidity is often regarded in the light of their respective oxygen-absorbing potentialities as indicated by the degree of unsaturation of the fatty acid constituents of the glycerides. Everything e1.e being equal, this probably would hold true were it not for the fact t h a t some oils, notably soybean, show a resistance not in keeping with their degree of unsaturation. I t is reasonable t o suppose t h a t this may be due to the presence of natural antioxidants. I n recent years the peroxide test has come into daily use in oil laboratories as a measure of the degree of oxidation of oil or fat and as a better iiiea,sure of rancidity than the older Kreis test. The iodine liberated from potassium iodide under definitely prescribed condition. ser7-e’. as a measure of the peroxide
VOL. 28, NO. 8
present; result’s are reported in millimoles of peroxide per 1000 grams of oil. Corn oil has long enjoyed advantage over other food oils; for in spite of the fact t h a t i t is one of the more unsaturated oils (with an iodine number of about 128), i t exhibits a greater stability than other oils characterized by a greater proportion of saturated acids. It is noteworthy t h a t in 1930 Mattill and Crawford (6) concluded t h a t corn oil contains a powerful antioxidant. I n a recent study in the writer’s laboratory i t was found that, soybean oil evidenced a slower rate of peroxide formation than even corn oil. Samples (250 grams each) of freshly refined soybean and corn oils, with a peroxide value of less than 0.2, were subjected to uniform stirring in a constant-temperature cabinet held a t 85’ C. The samples were spaced equidistant from a 200-watt lamp, and the air over the samples was kept in motion. Thus the severe factors of light, heat, and exposure to air t’o induce a rapid oxidation of the oil were present. After 24 hours the soybean oil tested 21 millimoles peroxide, whereas the corn oil showed 43; at’the end of 2 days 56 against 81; and a t t h e end of 3 days 84 for soy against 116 for corn. oil. Repetition of such tests with 2 per cent raw soybean oil added to each gave rates of peroxide formation only one-quarter as great. This behavior indicates the existence of some natural antioxidant’in soybean oil not. entirely removed by the refining process. The foregoing is not an isolated test, but only a small part of a n investigation of the properties of this oil now under way. Studies of this nature serve to point out that, oxidation is probably not the answer to the flavor problem of soybean oil, at least not’ in the 5ense t h a t oxidation causes rancidity in most oils. Domestic soybean oil contains about 2.3 per cent of t h e highly unsaturated linolenic glyceride, with three double bonds, and 51 per cent of linoleic glyceride, with two double bonds. Corn oil, with about 40 per cent linoleic, contains nearly as much of this acid as soybean oil, but no linolenic. K e might assume t h a t t h e development of flavor in refined soybean oil is due to its small content of linolenic glyceride, whereas corn oil, with none of the highly unsaturated linolenic acid, does not develop the objectionable flavor. The presence of three highly reactive double bonds leads us t o speculate about the possible flavors of compounds due to condensation, ring formation, or even kebone structures, presuming a slight amount of initial oxidation. We might assume the possibility t h a t traces of such compounds can have a very apparent odor or taste. The answer may be selective hydrogenation, reducing the small amount of the highly unsaturated linolenic constituent to linoleic. This is difficult to do without proportionately saturating t h e linoleic glyceride which constitutes more than half of t h e oil. At the same time the oil would be changed from a true qalad oil to one with stearine (because of inooleic glyceride formed), and fractional crystallization would be required. Furthermore, even when highly saturated, soybean oil is said to have a persistent “tallowy” flavor when compared with hydrogenated cottonseed oil. This i. a research problem of major importance. The reTvards of success will be great, for, if the reversion difficulty can be entirely overcome, domestic soybean oil will have an established place among the oils of the food induntry.
Food Accessory Value of Unsaturated Oils Biological chemists have come forward with a good word for the more unsaturated oils, among which soybean oil is
AUGUST, 1936
INDUSTRIAL AND ESGINEERING CHEVfISTRl-
classified. Ander>on and TVilliams (1) report convincing evidence that the animal organism cannot' synthesize either linoleic or linolenic fa.tty acids, both of which are indispen5able. Quoting Burr and Burr (S), they prove that certain fatty acids are indispensable for living animal organisms: "When rats were reared on a fat-free diet, a deficiency disease developed which had not previously been described. This di>ease is rather specific &ice a, scaly condition of the skin develope, while growth continues a t an approximately normal rat'e. Later the tail often becomes necrotic and the kidneys degenerate." Saturated fatt'y acids are ineffective. but eit'lier linoleic or linolenic acid. are t'he outstanding curative or prophylactic agents; so they conclude that warm-blooded animals are unable to Yynthesize linoleic and powihly other of the more highly unsaturated acids. There is much evidence in the literature indicating the advisability of leading the food habits of the general population away from solid fats toward a greater w e of oils, particularly those containing the badly needed linoleic glyceride. It is perhaps significant that those peoples known for the excellence of their cooking instinctively prefer to use liquid oils rather than lard or more modern synthetic vegetable shortenings. It would seem, then, that' a rapid growth in the volume of soybean oil in the national dietary should be distinctly beneficial to the general population. 0
903
Sunimarizing briefly, appareutly a young giant ha* stepped into the picture of agricultural products of our country. Rapid as has been the growth of the newcomer, both the producer on one hand, and the conwmer on the other, have made a sturdy effort to adapt domestic soybean oil to commercial demands. B u t industry still needs help from research. Where the rewards are so great there can be no question but that help iq on the way.
Bibliography (1) .Inderson, W.E . . and TTillianis. H . H . , Oil aiid S o a p , 12, S o . 12, 282 11935). ( 2 ) Baughman.' K.F.. and Jamieson. G. R.,J . . ~ J J ! . C'heni. Soc., 44, 2947 11922). \-~--, ( 3 ) Burr, G . O., and Burr, SI. SI.,J . B i d . C ' h e m . , 86, 587 (19303. (4) Eisenschiml. 0.. Paint. Oil Cheiii. Rea.. 87, S o . 11, 12-16 (,1929). ~
( 5 ) Jamieson, G. J., and SlacKinney, R. S.,Oil and Soap, 12, No. 4, 70 (1935). (6) Slattill and Craxford, ISD. ESG. C'HEX., 22, 341 (1930). (7) Stewart, C. S., Burlison. TI-. L., Norton, L. J..and Walin, 0. Unir. Ill. .Igr. Espt. .Sta.. Bd1. 385 (Dee.. 19321. (8) U. S. Dept. -Igr., Tearhook of Igriculture for 1931, paragraphs 557-9. (.9) Tushkevich. S . , FettcFie!ii. T - m s c i i n i i . 40, 197-200 (1933).
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SOYBEAN OIL and the Paint Industry E. E. WARE The Sherwin-Williams Company, Cleveland, Ohio
P
A l S T interests early realized the necessity for the development of a substitute for linseed oil and the ext'reme desirability of promoting a home-grown product for that purpose. The Paint Manufacturers' Association sponsored experi' mental plantings of soybeans as early as 1910, and the L~ cieiitific Section of the association published a number of circulars dealing with the properties of soybean oil and its utilization in paint products. Comparatively little progress was made from 1910 to 1930 because little domestic oil was available; even after it became available in comrnercial quantities, both it and the foreign oil were handled more or less as an unavoidable by-product whose properties were variable and! in a measure, beyond the control of the producer. The enormous increase in soybean acreage duriiig the past few years brought with it, many problems: some are still unsolved. Since most soybean industrial and food products clemand a relatively oil-free nieal, and animal hushandry experimentation has demonetrated to the farmer thai; he should feed meal rather than the full bean, the utilization of the byproduct soybean oil has become of primary importance. Alt'hough the coiisuinptioii of oils of various'types by paint, varnish, and lacquer iiianufacturers is relat,ively small in comparison with the consumption of fats and oils in other directions (approximately 8 per cent), Burlkoii and other early American iiir-est igators concentrated their efforts on proring
the iuitability of soybean oil for paint purposes rather than parallelirig the research of European and Oriental workers. ~ v h ofavored food products and ,soap, with the result that the general American public has crmie to consider paint as the natural and economic outlet for the oil froni this important farm crop. The Illiiiois Experiment' Station paintings, d i i c h suppleiiiented the early experiments of Gartliier and Ladd, proved that soybean can be used in high-grde paints, and, to a degree, they have outlined the limitations in the use of the present-day product. Considerable publicity was given to the soyhean oil paints
Soybean oil is not ideal for paint use because of poor drying qualities, but it does possess the excellent characteristics of permanent elasticity and freedom from discoloration. A t present it is seldom used alone; it is either blended with oils of better drying qualities or as a constituent of a synthetic resin vehicle. The utilization of soybean oil in paints and varnishes will progress through pressure of popular opinion and as a result of agricultural and industrial research in the improvement of the product.
