History of Soy Lecithin - Page 1
by William Shurtleff and Akiko Aoyagi
A Chapter from the Unpublished Manuscript, History of Soybeans and
Soyfoods, 1100 B.C. to the 1980s
©Copyright 2004 Soyfoods Center, Lafayette, California
WHAT IS SOY LECITHIN?
Lecithin is the popular and commercial name for a naturally occurring mixture of phosphatides (also called phospholipids or, more recently by biochemists, phosphoglycerides), which varies in color from light tan to dark reddish brown and in consistency from a fluid to a plastic solid. Lecithin is the gummy material contained in crude vegetable oils and removed by degumming. Soybeans are by far the most important source of commercial lecithin and lecithin is the most important by-product of the soy oil processing industry because of its many applications in foods and industrial products. The three main phosphatides in this complex mixture called "commercial soy lecithin" are phosphatidyl choline (also called "pure" or "chemical" lecithin to distinguish it from the natural mixture), phosphatidyl ethanolamine (popularly called "cephalin"), and phosphatidyl inositols (also called inositol phosphatides). Commercial soy lecithin also typically contains roughly 30-35% unrefined soy oil. Indeed lecithin is one of the most complex and versatile substances derived from the soybean.
Etymology and Nomenclature. The word "lecithin" is derived from the Greek term lekithos meaning "egg yolk." In 1846 Gobley isolated lecithin from egg yolk and in 1850 gave it its present name (Maclean and Maclean 1927). In the late 1800s it was also spelled "lecithine" in English, a spelling that is still used (conveniently) in German to refer to the pure or chemical lecithin (Kunze 1941). In present-day English, the term "lecithin" has two different meanings, which can be confusing. To most food processors and chemists it refers to the natural complex mixture of phosphatides, but to most regular chemists, biochemists, and pharmacists it is a trivial term for the chemically pure phosphatide, phosphatidyl choline. In this chapter we will consistently use the term "lecithin" in its broader sense, to refer to the natural complex. The commercial term "soybean phosphatides" may be used to denote the oil-free lecithin complex.
Manufacture. Lecithin is obtained in the process of degumming crude soy oil, usually at the refinery of the company making commercial lecithin rather than at the oil mill. Crude soy oil contains an average of 1.8% (range 1.2-3.2%; Bailey 1951) hydratable compounds, primarily lecithin phosphatides. Roughly 1% of live steam or warm water is added to the crude soy oil at about 70*C, in a batch or continuous process. The emulsion is then agitated or stirred for 10-60 minutes as the phosphatides hydrate and agglomerate, forming a heavy oil-insoluble sludge, which is separated from the oil by use of a centrifuge. The sludge coming from the degumming centrifuge, a lecithin and water emulsion containing 25-50% water, may then be bleached once or twice, typically with hydrogen peroxide, to reduce its color from brown or beige to light yellow. Fluidizing additives such as soy oil, fatty acids, or calcium chloride can then be added?? to reduce the viscosity to that of honey and prevent the end product, on cooling, from being a highly plastic solid. Finally the product is film or batch dried to reduce the moisture to about 1% (Szuhaj 1980). Whether bleached or not, the finished commercial product is called "unrefined lecithin" or "natural lecithin;" it contains 65-70% phosphatides and 30-35% crude soy oil. The oil in unrefined lecithin can be removed by extraction with acetone (phosphatides are insoluble in acetone) to give a dry granular product called "refined lecithin."
Varieties of Lecithin and Their Composition. All varieties of soy lecithin can be classified into three broad types: unrefined or natural (including bleached varieties), refined, and chemically modified. Unrefined or natural lecithin comes in six basic varieties, long defined by specifications of the National Soybean Processors Association: plastic or fluid, each either unbleached, bleached, or double bleached. (Because fluid lecithins are easier to handle and dissolve more rapidly in various solvents, only small amounts of plastic grades are now produced.) Refined lecithin (which has had the oil removed using acetone) comes in three basic varieties: custom blended natural, oil free phosphatides (as is or custom blended), and alcohol-fractionated oil-free phosphatides (as is or custom blended). These latter special refined grades, which may contain 60-99.7% phosphatidyl choline, are used mostly for pharmaceutical applications and research (Brekke 1980). Chemically modified lecithin products, altered through selective chemical treatment, improve lecithin's compatibility to certain systems. Szuhaj (1983), using another method of classification, has noted that in addition to the six basic types of natural or unrefined lecithin, there are six types of upgraded lecithin products, including clarified lecithins (filtered), fluidized lecithins, compounded lecithins, hydroxylated lecithin, deoiled lecithin (granular), and fractionated lecithin. Recent composition figures for both unrefined (natural) and refined (deoiled) lecithin are given in Figure 28.1. Interestingly, earlier publications (Erdahl 1973 in Wood and Allison 1981; Brian 1976) showed these two products to contain significantly higher percentages of the three major phosphatides and no glycolipids.
Lecithin is also available as a dietary supplement in two forms: as granular lecithin (oil-free refined lecithin with calcium phosphate as a flow agent) and as capsules, containing a dispersion in oil (Wood and Allison 1981).
Fig. ??.?. Composition by Weight of Unrefined and Refined Soy Lecithin
|Oil-Free Compound||Unrefined Lecithin||Refined Lecithin|
|Unrefined soy oil||31-34%||0-3%|
|Neutral lipids (mostly triglycerides)||2-4%|
Source: B.F. Szuhaj (1982), Central Soya Co., Inc. Lecithin Div. Fort Wayne, Indiana. Personal communication.
Structurally, the phosphatides in soy lecithin consist of glycerides (the basic component of soy oil; see Chapter 40) in which one fatty acid radical has been replaced with phosphoric acid. In the case of pure or chemical lecithin (phosphatidyl choline), the phosphoric acid is further esterified with choline; in cephalin it is similarly esterified with cholamine. Lecithin is composed mostly of fatty acids, and they are in roughly the same proportion as in soy oil; 50-57% linoleic and 5% linolenic.
Natural Sources of Lecithin . The most concentrated natural and unrefined sources of lecithin are soybeans (1.48 to 3.08% lecithin), peanuts (1.11%), calf liver (0.85%), wheat (0.61%), oatmeal (0.65%), and eggs (0.39%) (Wood and Allison 1981). The human spinal cord contains 6-10% lecithin and the human brain 4-6% lecithin in fresh substance. Among refined substances, especially concentrated sources of lecithin include dehydrated (powdered) egg yolk (14-20%), natural egg yolk (7-10%), wheat germ 2.82%, soy oil (1.8% but 2.65% including the 30-35% entrained soy oil??), and butterfat (1.4%). Soy oil has the highest lecithin and phosphatide content of any known oil; other vegetable oils average 0.5% lecithin. Unlike animal phosphatides, soybean phosphatides contain no cholesterol. In plant seeds the phosphatides are largely associated with oil, but strangely their content varies roughly with the protein rather than the oil content (Stanley 1950). Moreover, all of the above indicates that phosphatides and lecithin appear to be closely connected with the most important vital and reproductive organs and processes. In addition to the spinal cord, brain, eggs, and seeds, they are also concentrated in the nerves, liver, kidneys, and sperm. Actually, lecithin is found in the cell membranes of all human cells, and they tend to be most concentrated where membrane functions are specialized. Lecithin compounds are also closely associated with fatty acids in the body.
Functional Properties . Lecithin is a multi-functional surface-active agent. Each molecule has, like Janus, two faces. The fatty-acid portion of the molecule is attracted to fats (it is lipotrophic) and the phosphoric acid?? portion is attracted to water (it is hydrotrophic). Because of this dual nature, lecithin molecules tend to position themselves at the boundary between immiscible materials, such as oil and water. There they serve many useful functions through a surface modifying effect. According to Szuhaj (1980, 1983) lecithin serves the following major functions: (1) Emulsifying allows the mixing of otherwise immiscible substances, especially in water-in-oil systems, such as margarine and chocolate. This is the most widespread of its various uses; (2) Solubilization makes it possible to dissolve oils (such as flavor oils and oil-soluble colors) in water; (3) Suspension , for example, keeps pigments dispersed in paints, preventing agglomeration; (4) Wetting/instantizing helps powers to dissolve quickly in water; (5) Lubrication and Release ; when lecithin is applied in a thin film to a cooking utensil or a mold, it promotes release of food or other materials from that surface; (6) Crystallization Control is used especially to control the crystallization of sugar in fat systems, as in chocolate; (7) Complexing tends to retard crystallization of starch associated with staling in baked goods. (8) Anti-spatter , as in margarine; (9) Viscosity Modifying ; and (10) Therapeutical . It also serves as a stabilizer in ice creams and shortenings and an antioxidant in oils and fats.
Food Uses . Lecithin is used in a surprisingly large array of our daily foods. Perhaps most widely used in margarine (for anti-spatter and as an emulsifier), it is also used in chocolates, caramels and coatings (to control viscosity, crystallization, weepage, and sticking), in chewing gum (for its softening, plasticizing, and release effects), in instant foods such as cocoa powders, coffee creamer and instant breakfast (for wetting, dispersing, and emulsifying), in calf milk replacers (to add energy and aid digestibility and emulsification). It is also found in baked goods, cheeses, meat and poultry products, dairy and imitation dairy products, and still other products (Stanley 1950; Brekke 1980; Szuhaj 1980, 1983).
Therapeutic Uses . Much research has been done and is being done on the therapeutic use of lecithin, especially in the prevention or treatment of neurochemical and cardiovascular orders. Although the results are not conclusive, many health food consumers use lecithin for benefits they believe it will bring in these areas.
Nonfood and Industrial Uses . In this realm there are at least as many applications as in the food industry. Lecithin is used in cosmetics, pharmaceuticals, coatings (paints, magnetic tape coatings, waxes, polishes, wood coatings), plastic and rubber industry, glass and ceramic processing, paper and printing, masonry and asphalt products, petroleum industry, metal processing, pesticides, adhesives, textiles, and leathers (Stanley 1950; Brekke 1980; Szuhaj 1980, 1983).
World Production . The major countries refining soy oil (USA, Western Europe, Japan) are also the major producers of soy lecithin. Stanley (1950) estimated that in the year 1936-37 the world produced 1,787,000 tonnes (metric tons) of soy oil. From this it recovered 1,814 tonnes of lecithin and left 47,174 tonnes unrecovered, thereby utilizing only about 4% of potential production. The main producers were the USA, Germany, Japan, Denmark, and Norway. In 1948 world soy lecithin recovery was estimated at 4,535 tonnes, and plant derived lecithin other than soy was estimated at one-fifth this amount. Recovery and utilization of soy lecithin was thought to be less than 10% of potential production. In 1976 Van Nieuwenhuyzen (in Brekke 1980) estimated world recovery of soy lecithin to be 90,700 tonnes a year, from 8.8 million tonnes of soy oil produced containing 233,200 tonnes of soy lecithin. Thus roughly 39% of the total lecithin was recovered and used. Clearly the percentage used has been increasing, but the majority that could be recovered is not yet used directly. The unsold portion is mixed back into defatted soybean meal, which is used for livestock fodder. Although this practice is not widely discussed by the industry, the lecithin is not considered a negative nor a positive factor.
HISTORY OF SOY LECITHIN IN EUROPE
The world's earliest research on and production of lecithin and soy lecithin was done in Europe, with first France, then Germany leading the way.
Early Research (Pre 1900) . The first indication of the occurrence of complex fatty acids was obtained by the Frenchman Fourcroy in 1793 and in 1812 Vauquelin succeeded in isolating phosphorous-containing fats from the brain. Fremy in 1841 called one of Vauquelin's compounds "oleophosphoric acid." The actual discovery of lecithin, however, is credited to the Frenchman Gobley. Gobley (1846, 1847 Refs??) isolated from egg yolks a soft, viscous, orange colored substance which made an emulsion with water. In 1850 he named it "lecithin." (Maclean and Maclean 1927). Later Gobley found similar substances in the brain of birds, sheep, and humans, in the eggs and milk of carp, in blood, gall, and edible snails. He realized that lecithin was a mixture of substances. In Germany the lecithin described by Gobley was first investigated precisely in the laboratory of Hoppe-Seyler in Tubingen. Diaknow (1867-68 Ref??) succeeded in obtaining very pure lecithin from egg yolk, caviar, and brain, and in proving that the nitrogen-containing portion was choline (Kunze 1941). The classical European treatises on lecithin (such as Thudichum's A Treatise on the Chemical Constitution of the Brain , of 1884 Ref??) dealt mostly with the phosphatides of animal origin.
The earliest known reference to the presence of lecithin in soybeans was published by Schulze and Steiger at Zurich, Switzerland, in 1889. In an article on the lecithin content of plant seeds (in German), they reported in passing that soybeans contained small quantities of lecithin, which they measured in terms of its content of magnesium diphosphate (Mg2P2O7^). In 1894 Schulze and Frankfurt reported that soybeans contained 1.64% lecithin by weight. In 1897 Hanai in Japan, in the first English-language publication mentioning soy lecithin, cited Schulze and Steiger in noting that "Seeds rich in starch generally contain much less lecithin than such as are rich in proteid, thus barley grains contain less than half the amount of lecithin that soja-beans do. Probably there is also a larger proportion of lecith-albumin in the seed of soja and lupin than in those of squash and barley." In France the soy pioneers Li and Grandvoinnet noted in 1911-12 that "Soybeans contain a notable quantity of lecithin, as pointed out by various authors."
1900-1939 . As the soybean crushing and soy oil refining industries in Europe expanded from 1908 on, ever larger amounts of sludge from the degumming soy oil were produced. There were major problems in disposing of this since it tended to ferment and smell bad. Plants in Germany decided to dry this sludge under a vacuum and rename it "soybean lecithin." The manufacture of lecithin from mechanically pressed soy oil was expensive because it required the use of several solvents, evaporations, and other steps. However the installation of solvent extraction plants for processing soybeans in Germany in the early 1920s furnished a convenient means of separating and purifying soy lecithin without the use of solvents. Germany led the way in the development of lecithin recovery in large part because the country also pioneered solvent extraction (Eichberg 1947).
Interestingly, the earliest processes and patents related to lecithin involve its extraction from soybean cake or flour, rather than from oil. In about 1915 G.F. Hildebrandt in Hamburg, then Germany's main oilseed crushing center, developed a process for the purification of crude lecithin removed from soybean cake or flour. Details of the process are not known (Matagrin 1939). In 1919 Baumann (Bollmann??) and Grossfield (Crossfield?? Ref??) patented a process for the extraction and purification of lecithin from soy cake or flour (British patent 144,225. July 11), using a solvent and ethyl acetate, which separated the oil and the phosphatides. Later important refinements on the process were made in 1927 (German patent 505,354) and 1933 (French patent 759,007). Also during this early period, in 1921, Mueller in Germany described a process for using a lecithin to give margarine a butter-like aroma--a unique and intriguing concept (Matagrin 1939).
The first person to envision the possibility of commercial production of lecithin from soybeans and to develop practical processes and equipment therefore was Hermann Bollmann, of the Hanseatische Muehlenwerke (Hansa Muehle^) in Hamburg, Germany. His work led to the development of an entirely new source of phosphatides and of lecithin, this time from plants. On 8 October 1923 Bollmann was granted German Patent 382,912 for the extraction of soy lecithin from soy oil. Previously, in August of that year, he had been granted a similar patent in the USA. Bollmann originally used a combined solvent of about 2 parts ethanol (ethyl alcohol) and 3 parts benzol or a volatile liquid hydrocarbon on the theory that the residual meal would be more palatable. Also this combined solvent gave a larger lecithin yield than hexane, which was widely used after 1935 (Eichberg 1939). The solvents were evaporated from the miscella and steam was injected into the crude oil to hydrate the phosphatides, which were removed in the early days by settling out, later by centrifugation. Finally they were dried under a vacuum at about 60*C to obtain a brown viscous liquid. The early lecithin was not of much value since the extensive heat to which this heat-sensitive substance was subjected often turned it dark brown and caused it to smell bad. However in 1909 and 1911 H. Buer had pointed out the heat sensitivity of lecithin and been granted Swiss (No. 47,785) and German (No. 261,212) patents for a method to obtain a (non-soy) lecithin almost free of flavor and odor. Bollmann, who was also aware of lecithin's heat sensitivity, and subsequent researchers built new equipment to operate at lower temperatures. Using this, plus new methods incorporating Buer's (see Bollmann's German patent 485,676 of 1929), a high-quality soy lecithin was finally obtained. Bollmann's process was perfected by Bruno Rewald (US Patent 1,895,434. 24 Jan. 1933), who had gone to work for Hansa Muehle^ as chief chemist shortly after Bollmann patented his lecithin recovery process. Bollmann worked on processes to recover lecithin and Rewald did research on how to improve and apply it. Rewald's 1933 patent used a centrifuge and an acetone wash to ingeniously protect the phosphatides from oxidation.
Apparently commercial production of soy lecithin began in Germany in about 1923, at the time Bollmann was issued his patent, for in 1925 Levene and Rolf in New York reported that Bollmann had supplied them with a "considerable quantity of commercial lecithin obtained from soy beans." They analyzed this product and described its principal characteristics (relative to the then standard commercial lecithin derived from egg yolks) as "the low proportion of saturated fatty acids, the absence of unsaturated fatty acid containing a longer carbon chain than C-18, and the presence of linolenic acid." In addition to pure lecithin the commercial product was also found to contain cephalin.
In the early days great difficulty was experienced in finding uses for lecithin. Since the early 1900s there had been considerable interest in the possible health benefits of lecithin as a food supplement. This interest stemmed largely from the physiological observation that relatively large amounts of lecithin were found in the human brain (first reported in 1884), the liver, and the sheaths surrounding nerve fibers. Starting in the 1920s, considerable research on the therapeutic value of lecithin was published in Europe, especially in Germany. (Unfortunately, little of it has been translated into English or cited in English-language documents, perhaps because of equivocal results.) Initially it was thought that lecithin could be used in "nerve tonics" like sodium phosphates and phytin, or to help reduce the effects of alcohol intoxication (Horvath 1927). In 1934 Ma and co-workers in China published a curious article on "A Comfortable and Spontaneous Cure for the Opium Habit by means of a Lecithin" in an English-language medical journal. The treatment, which called for 20-30 gm of soy lecithin taken orally after each meal, could have created a huge demand if prescribed for all Chinese habituated to opium. Actually these various therapeutic uses consumed very little of the fledgling product.
Starting in the mid-1920s, at the same time that therapeutic uses of soy lecithin were attracting considerable interest, much more important research on food and industrial applications was getting underway. Most of this early research and development was done in Germany, then the world leader in the field, but only a small fraction of it was published, since the aim in most cases was the securing of patents by private companies (Horvath 1935). By 1939 more than a thousand new uses for lecithin had been discovered, and many patented. A large proportion of the early patents were granted to Bollmann and, after 1930, to Rewald, often jointly with his Hansa Muehle^ co-worker, and usually in a number of countries, including the US. As early as 1924 Bollmann pointed out that the addition of small amounts of lecithin to refined oils (from which the lecithin was removed) retards rancidity (US Patent 1,575,529). His discovery of a method for purifying phosphatides and refining lecithin was another important advance (British Patent 259,166 of 1925, also patented in Germany on 14 April 1925). Applications for lecithin in tanning leather (1928), improving macaroni (1928), and for textile production (1933-34) were other early advances (Stanley 1950).
Prior to 1930, the term "lecithin" in commercial directories referred to egg yolk lecithin. While egg yolks themselves were fairly widely used in mayonnaise, some dressings, and some margarine, egg yolk lecithin was never much more than a laboratory curiosity and a costly pharmaceutical. In addition to being expensive, egg and animal lecithins do not keep well and they have a disagreeable odor and taste. Although soy lecithin could not replace egg yolk in all its applications, it did generally replace egg yolk lecithin after 1930 as the standard commercial lecithin. Moreover, it was the first lecithin of any type to find widespread commercial application.
Soy lecithin's first major market in Europe was in margarine. It was used experimentally as early as 1925 by small margarine manufacturers in Hamburg, Germany. The use of egg yolk in margarine was first patented in Germany in 1884 Ref??. A few tenths of a percent of soy lecithin in margarine aided emulsification in this water-in-oil (20:80) emulsion, prevented splattering during pan frying (the explosive evaporation of water when finely dispersed particles form large droplets), improved browning of milk solids, and kept the latter from lumping and sticking. Working (1936) noted that "In margarines without lecithin there is a marked tendency for the water to drain out and evaporate, leaving the salt on the wrapper instead of in the margarine." Horvath (1935) noted that more than 454,000 kg (1 million lb) were then being used annually in the German margarine industry. By 1930 lecithin was also widely used by the chocolate and cocoa industries, especially in England. It improved the wetting and dispersing properties of cocoa powder, partially replaced expensive cocoa butter, aided emulsification, and reduced "weepage" or "chocolate bloom" (Morgan 1930).
By 1932 Hansa Muehle^ had introduced and patented a line of three commercial lecithin products: Emulex, a dark, thick lecithin was used in paints and printing; Lecivon had a wide range of uses; and Splendicithin, a fluid product, was used with textiles. By the mid-1930s lecithin (sometimes with cholesterol) was the rage in European beauty products such as skin creams, "nutritive" creams, beauty soaps, and cosmetics; it provided better softening and penetrating properties. By 1938 lecithin was being used by the rubber and leather industries.
By 1934 Europe's major soy lecithin producing countries were Germany, Denmark, England, and Norway. In 1930 the Austro-Hungarian soyfoods pioneer Berczeller was granted a patent for lecithin in Britain (No. 361,956, Aug. 25).
Amadee Matagrin played an important role in introducing and popularizing lecithin in France. He discussed its many applications in a scientific article in 1936, then in 1939 wrote an excellent book Le Soja , that mentioned soy lecithin in the subtitle. It contained a 26-page review of the literature on soy lecithin plus a bibliography of 31 references and a discussion of uses of soy lecithin worldwide.
1940-1983 . In 1941 Kunze published a remarkable 166-page book titled Lecithin , in German, which showed vividly the extensive scientific research done in Germany on all aspects of lecithin, primarily soy lecithin. There was a detailed 22-page section on therapeutic uses of lecithin, including its connection to the blood and its components, to the heart and vascular system, nervous system, digestive system, and to other systems and organs. The book cited over 1,000 references, including roughly 695 on the physiological and therapeutical uses and use possibilities of lecithin. Kunze noted: "Today most of the lecithin in trade is obtained from soybeans. The rise of soy oil production finally made lecithin a substance available in large quantities at low prices, since lecithin must be removed anyway from soy oil to give a good quality product. In 1941 the German margarine industry alone used about 500 tonnes of lecithin."
Interest in the possible therapeutic value of lecithin was stimulated in the mid-1970s when Natterman, a German lecithin marketing company, hired many scientists at various clinics to research their lecithin and write scientific articles about it. In 1975?? a symposium was held in Belgium and the proceedings were published in a large book edited by Peeters (1976). Though much of the research was well done, the entire project raised a storm of controversy. First, the company and scientists have coined a new term, "Essential Phospholipids," which was not considered scientific or valid, since phospholipids, made in the body from dietary lipids and phosphorus, had never been shown to be an essential component. Second, the entire project was considered somewhat contrived, with "paid for" conclusions. The result was that in the following years many other researchers went out of their way to look for negative aspects of lecithin to counter what some considered commercial "propaganda."
During World War II Germany's mighty lecithin industry, centered in Hamburg, had been reduced to rubble by Allied bombs. Hansa Muehle^ was largely destroyed; after the war it was renamed Oelmuehle^ Hamburg. By the 1950s the industry was back on its feet; the main application of lecithin once again was in margarine (Bailey 1951). Small amounts of rapeseed lecithin were produced in Germany and peanut lecithin in England, but soy lecithin increasingly dominated the trade.
In 1983 Europe's largest lecithin producer by quantity was the Unimills division of Unilever. Lucas Meyer GMBH was second, and N.V. Vamo Mills was third. Lucas Meyer, however, is not actually a manufacturer of lecithin and never has been. They buy unrefined lecithin from oil mills for resale and in some cases for blending or refining. Thus they are large sellers of lecithin, with the world's largest product range and largest worldwide sales. They have plants in Germany, Netherlands, France, Spain, the UK, and the USA (Decatur, Ill.). Headquartered in Hamburg, Lucas Meyer started processing lecithin for food use in 1949 and for industrial use in 1952. Unilever uses large amounts of its lecithin in its own products and also sells to others. A list of Europe's large lecithin manufacturers is given in the current issue of the Soya Bluebook .