History of Soybean Crushing: Soy Oil and Soybean Meal - Part 8

by William Shurtleff and Akiko Aoyagi


A Chapter from the Unpublished Manuscript, History of Soybeans and
Soyfoods, 1100 B.C. to the 1980s


Copyright 2007 Soyinfo Center, Lafayette, California

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Linoleic Acid. One important benefit resulting from the shift from animal fats to vegetable oils is the increased consumption of linoleic acid. Rich sources of this essential, polyunsaturated fatty acid are safflower oil (78% of its fatty acids are linoleic acid), sunflowerseed oil (75%), corn oil (59%), and soy oil (50-55%). Of all the dietary lipids, linoleic acid is the only one which cannot be synthesized by the body; if it is not supplied in the diet, deficiency symptoms can occur. For this reason linoleic acid is called an "essential fatty acid." Fortunately only very small amounts (less than 5 gm a day) are required by the body; deficiencies are rare. Research starting in the mid-1960s showed that linoleic acid is an important nutritional factor in minimizing or preventing coronary heart disease and several pathological conditions linked with it: hypertension, high blood cholesterol levels, arterial thrombosis, and maturity onset diabetes. Linoleic acid is also a precursor of prostaglandins, extremely important fatty acid hormones first discovered in 1964. Prostaglandin E1 reduces the tendency for blood platelets to aggregate and thereby combats coronary heart disease (Vinson 197?? Ref??). If there are not adequate levels of linoleic acid in the diet (which is highly unlikely), trans fatty acids present in hydrogenated soy oil products (see below), may exert harmful biological effects (as discussed in Chapter 27).

Trans Fatty Acids. When soy oil (or any oil??) is hydrogenated, trans fatty acids are inevitably produced; the amount and type varies with the type of hydrogenation. Such fatty acids are not found in nature in vegetable oils, although they are found in small quantities in some animal fats. More than 75% of the soy oil consumed in the US is partially or fully hydrogenated. The heated debate over the safety of trans fatty acids, which started in the 1970s??, is discussed in the next chapter under hydrogenation.

Chemical Additives. As noted earlier, chemical additives were increasingly used in oils from the 1950s. Despite the fact that all additives used in soy oil and related products are approved as safe by the Food and Drug Administration, most have not been tested for carcinogenicity and some are banned in Europe (National Research Council of the National Academy of Sciences 1982; Ref=Jaco??). BHA (antioxidant) may be unsafe and BHT may cause cancer; both are outlawed in West Germany. Thus a growing number of consumers, preferring not to gamble with their health, began to look for oils without additives and a growing number of oils began to be marketed as containing no antioxidants, antifoaming agents, or other additives. It is important to realize, however, that a rancid oil without antioxidants could be less safe than a good quality oil with antioxidants. Why?? Moreover, a number of additives (such as citric acid) need not be listed on labels.

Oil Abuse. It is the consensus among researchers, based on numerous tests, that oils (including soy oil) heated to the normal temperatures for the time periods used for baking and frying are completely safe, despite the presence of low levels of compounds that have been identified as potentially toxic. Only those that are "severely abused" by heating until they smoke or burn or by being used repeatedly without filtering until they become strongly oxidized have been shown in animal studies to be toxic; they produce growth inhibition and organ dysfunction, and may be carcinogenic (Emken 1980). All oils and fats break down/rancidify?? in proportion to the time and temperature used in frying; their fatty acids oxidize and the smoke point drops. Oils should always be used below their smoke point, which for most well-refined vegetable oils is 215*C (420*F) or higher. Butter has a low smoke point, due to short chain fatty acids.

Natural/Health Foods Market Concerns. In addition to sharing the above-mentioned concerns about the safety of oils and fats, some consumers who shop at natural and health food stores also tend to be concerned about hexane residues in solvent extracted oils and chemicals used during typical oil refining. There is very little information published about hexane residues in oils. Bailey (1962) reported that hexane solvent leaves a residue upon evaporation of less than 16 parts per million, typically 5-10 ppm. Ryder and Sullivan (1962) reported that hexane solvent contained less than 10 ppm of nonvolatile material (which would remain in the oil) but that it had been specially treated to remove the carcinogenic multi-ring aromatics (def??) which exist in untreated hexane; tests confirmed that none of these remained in the solvent, although Lijinsky and Raha (1961 Ref??) did find carcinogens at levels greater than 0.01 ppm. We know of no evidence showing that hexane residues in any solvent extracted oil are unsafe; if they were, the butter industry would have brought it to the public attention long ago. Nevertheless because of concern for possible long-term health problems, and because some customers prefer oils which retain their natural flavors, colors, and vitamins, many natural and health food stores carry at least one brand of mechanically pressed (usually expeller pressed) soy oil, which is typically quite expensive. It is typically produced by the same companies that produce most of America's oils, but under special specifications, then bottled, labeled, and shipped to natural or health food distributors (Schreiber and Fillip 1978).

Hain, a Los Angeles based health food company founded in 1926, for example, distributes two types of pressed soy oil. One labeled "natural unrefined" is simply expeller pressed, filtered, and bottled; it has a light brown color and fairly dominant flavor, which some people find to be "not unpleasant" but which makes others gag. The other Hain soy oil is fully refined after expeller pressing; it looks and tastes like any other soy oil. The label states "Contains No Preservatives;" it is not clear whether it contains antioxidants, defoamer, citric acid, etc. Hain also labels both these oils "Cold Pressed," a term which Hain apparently introduced into health-food trade oil labeling in the early 1950s, and which was soon picked up by other major sellers of oil to this market (Schreiber and Fillip 1978). The deceptive misnomer "Cold Pressed" is not used by the oil crushing industry (even those who do mechanical pressing), since during pressing the oil is heated to 65-72*C (140-160*F), although this is still much less than the typical 150*C (300*F) during evaporation in solvent extraction. Then, if "cold pressed" oil is deodorized during refining, it is heated to as high as 226*C (440*F). Deodorizing, however, also removes pesticide residues. This refined "cold pressed" oil, then differs from typical soy oil in that it was not solvent extracted and contained no hexane residues, no trans fatty acids from partial hydrogenation, and presumably no chemical additives. It would probably become rancid more quickly. If unrefined, it contained more of its natural antioxidants (during refining, bleaching, and deodorizing, some 20-52% of alpha tocopherols and 36% of total tocopherols/vitamin E, powerful natural antioxidants, are removed from soy oil), and more lecithin and fat soluble vitamin A. Yet it also had a dark color, a dominant flavor, and an undesirably high free fatty acid content. Unrefined oil smokes at lower temperatures, becomes cloudy more easily when refrigerated, goes rancid more rapidly, and may foam during deep frying. Clearly, then, there are tradeoffs, even for purists. The natural foods industry would be expected to take interest in some of the new non-toxic, non-petroleum-derived solvents (ethanol, water with membrane filtration, carbon dioxide) that are now being investigated, as discussed below.

The above health concerns with soy oil (and oils in general) have been listed in what we consider to be their descending order of importance. The bulk of evidence indicates that by far the most important problem is the very high level of total fat consumption. (Equally serious is the high level of calorie consumption, leading to obesity.)

Starting in the 1960s, a number of then relatively unimportant oils began to compete with soy oil on both the US and world markets: palm, sunflowerseed, and rapeseed. As shown in Figure ??.??, by 1982 palm oil was second, sunflowerseed oil was third, and rapeseed oil was fifth on the world market. Palm oil, produced mostly in Malaysia and Indonesia, was the strongest competitor because it was lower priced (in some countries), available in large quantities, and had by far the largest yield and value per acre of any oil crop with very low production costs since the tree bears for 35 years. High in saturated fatty acids (52-92%), palm oil was most widely used in shortenings, but use in cooking oils and margarines was increasing. US imports declined from a peak of 423,000 tonnes in 1975 to less than 163,000 tonnes in 1979. The development of new high-oil, higher yielding sunflowerseeds greatly expanded US and world production. Major producers are the USSR, USA, and Argentina. Both northern-grown sunflower and safflower oils have excellent P/S ratios, are high in essential linoleic acid (64% and 73%), and contain less than 1% linolenic acid. Rapeseed oil, long the preferred cooking oil in Japan, is produced in large quantities in Canada, China, and India. Traditionally the most important oilseed crop of Western Europe, the major producers there are France, Germany, and Sweden. New varieties of rapeseed (developed by breeding since 1960), which contain little or no undesirable erucic acid in the oil nor glucosinolates in the meal (what are these two?? why unwanted??), have greatly stimulated crop expansion and, since the late 1970s, made the rapeseed the soybean's leading competitor among oilseeds in the huge and lucrative Western European market. A move to change the seed's name to "canola" and the oil's name to "canola oil" may help improve its male chauvinist image.

In 1978 the value per acre of soybean oil and meal was $200; of this, $79 came from the oil and $121 from the meal. The following oil crops had a greater value per acre from oil and meal: oil palm $1,014, peanuts $432, safflower $432, corn $244, and sunflower $209. In 1978 the average yield of soy oil per acre was 285 lb. The following crops had higher yields per acre; oil palm 3,475 lb, peanuts 705 lb, safflower 680 lb, sunflower 525 lb, and rapeseed 365 lb. While these figures do not reflect the costs of producing the various oils and meals, they do indicate potential for competing oilseed crops.

Starting in the late 1970s, with rising petroleum prices, there was some interest in using soy oil as a renewable fuel in diesel engines. Tests showed that it would work by itself but, in part because of soy oil's high viscosity (it is 10 times thicker than diesel fuel), it was shown by investigations at Louisiana State, Kansas State, and Ohio State Universities to work best as an extender for diesel fuel, with the soy oil comprising 10-50% of the mixture. The main problem is that soy oil is presently much more expensive than diesel fuel, but the price differential is decreasing. Actually, soy oil was first used experimentally to run diesel engines in 1943. By 1981 it was being used commercially to extend diesel fuel in Brazil.

A series of studies initiated by the American Soybean Association in 1978 showed, surprisingly, that although soy oil is by far America's most widely used oil (accounting for 84% of all edible vegetable oils and 58.3% of all edible oils and fats in 1979), most consumers were simply not aware of how much soy oil they actually buy and use. When 1,200 female heads of households were asked "What oils can you think of?" only 17% mentioned soy oil (52% mentioned corn oil, 36% peanut oil, and 23% safflower oil), and only 7% reported having purchased soy oil in the past 6 months. When home economists (half from business, half from academia) were asked "What oils can you think of?," 37% of the business home economists and 46% of the academic home economists did not mention soy oil. Another survey (1979) of attitudes toward soy oil among hospital dietitians showed that 75% generally recommended corn oil in their professional practice, versus 28% for safflower oil and only 11% for soy oil. Although known to be lower in price, soy oil was also considered lower in quality (strong taste, heavy, greasy, oily) than the other two oils. Yet the dietitians who were most familiar with soy oil, recommended it more, although many did not realize that products they used widely at home contained soy oil. Still another ASA survey of consumers showed that soy oil was preferred over corn oil 52% to 39%, with soy oil being perceived as the lighter of the two oils. It was concluded that soy oil was perceived to be a top quality oil but that there was a great difference between the number of people who buy it and those who know what they are buying. Soy oil was rightly likened to "a king with no crown." It had total market dominance with very little recognition or image. The ASA Market Development Foundation promptly began a campaign to build a more positive image for soy oil, to increase recognition and product loyalty, and to encourage manufacturers to identify soy oil in product labels. Attractive color booklets and flyers of soy oil recipes and a newsletter "Soy What's News" for food communicators were published starting in 1981.

There are basically two reasons for this peculiar lack of recognition of soy oil. First, when soy oil became widely used in the US during the 1930s and 1940s, it was perceived as being of lower quality than other popular oils, so it was (and generally still is) marketed under the generic name "vegetable oil" or under a brand name (Crisco, Wesson). As early as 1936 Horvath noted: "It is regrettable that the industries using soya oil for margarine, salad oil, and mayonnaise never make mention of `soya oil' as a constituent of their products." Second, with the advances in oil refining techniques during the 1960s and 1970s, most oils came to be used interchangeably, often being chosen on a least-cost formulation basis. Use of the term "vegetable oil" rather than "soy oil" on labels allowed flexibility in formulation.

During the late 1970s and early 1980s considerable research was done to find alternatives to the use of toxic, highly flammable, and increasingly expensive petroleum-based hexane solvent. One process, developed at Texas A&M University involved aqueous processing of whole soybeans, followed by centrifugation and use of ultrafiltration to isolate the soy proteins. One disadvantage of the process in terms of oil extraction was that 5% less oil was recovered than with the conventional process (Lawhon et al. 1981). Another relatively new petroleum-free extraction process involves the use of high-pressure supercritical carbon dioxide. The first patent on the process was issued to Vitzthum and Hubert in Germany in 1972 (Ref??); a detailed analysis was given in 1982 by Friedrich et al. of the USDA Northern Regional Research Center. Advantages: Supercritical carbon dioxide is an ideal solvent because it is nontoxic, nonexplosive, inexpensive, readily available, renewable, and easily removed from the oil and meal. The extracted oil is lighter in color and contains less iron and one-tenth the phosphorus of hexane-extracted crude soy oil. Thus the crude oil is largely degummed, its yield is good, and operating costs of the system are low. Disadvantages: Sophisticated and expensive high pressure equipment and technology are required, so initial investment costs are high.

A promising new refining technique called "physical refining" or "steam refining," used since 1950 on palm and coconut oils, was increasingly widely used for refining soy oils by the late 1970s, especially in Europe. The process consisted of (usually) heat treating the soybeans prior to flaking to inactivate enzymes (urease, lipoxygenase, lipases), then after oil extraction replacing alkali extraction with a high temperature phosphoric acid/bleaching clay refining process, using a relatively large amount of clay (about 1.5%). Deacidification (neutralization) and deodorization are done together by steam distillation under a high vacuum at high temperature. The main advantage is the decrease in loss of neutral oil during removal of soaps. Other advantages: The process is quicker, took fewer steps and no wet separation, used less energy, required no soapstock splitting facility, and released much less environmental pollutants. The larger input of bleaching earth required was more than compensated for by the other savings (Leysen 1981). Disadvantages??

In 1982 the six leading food oils and fats produced in the US, in order of importance, were soy oil (64.8% of the total), cottonseed oil, lard, butter, edible tallow, and corn oil (Fig. ??.??). Since the 1950s the total production of lard, butter, and cottonseed oil had steadily decreased.

During this period there was an increasing use of soy oil in mayonnaise and prepared salad dressings. Mayonnaise is an oil-water emulsion which, by law, must contain at least 55% oil content by weight; most commercial mayonnaises contain 75-83% oil. They also contain 9.4-10.8% vinegar, 7-9% egg yolk, 1.5-2.5% sugar, 1.5% salt, 0.5-1.0% mustard, and 0.1-0.2% white pepper, all ingredients by weight. Imitation mayonnaises contain only 14-40% oil and much more water than most; starch paste is used as a thickener. In the US soy oil was first used in mayonnaise in the early 1930s (Horvath 1933). By 1980 a major use of soy oil was in mayonnaise. One company (Norganic Foods in Anaheim, California) sold a Golden Soya Mayonnaise exclusively to natural and health food stores.

Soy oil was also widely used in prepared salad dressings, both pourable (such as Russian or Thousand Island) and spoonable types. In 1978 a full 90% of all oils used in mayonnaise and prepared dressings were soy oil.

In the period from 1940-1980 use of soy oil in the US increased a remarkable 34-fold. But the greatest total increase took place from 1960-1980 when utilization leaped from 3,000 million pounds to over 8,000 million pounds. The most rapid gains during this period were for use as cooking and salad oils (starting in 1960 soy oil rapidly took over this market from cottonseed oil), and in prepared dressings, which by 1978 accounted for some 46% of all soy oil used; 30% of all soy oil was used in shortenings and 18% in margarines (Fig. ??.?? and ??.back).

Stated differently, in 1978, soy oil accounted for about 90% of all oils and fats used in prepared dressings, 83% of the oils used in margarine (corn oil was the second most widely used oil or fat with 10.9%), 80% of the oils in salad and cooking oils (cottonseed oil had 19.2%), and 62% of the oils in shortening (beef fats had 20.1%) (Fig. ??.??).

The amount of soy oil used for nonfood industrial purposes remained quite static between 1960 and 1978, averaging about 226,800 tonnes (500 million lbs), then fell to only 92,000 tonnes from 1979 on (Fig. ??.??). In 1980, industrial use of soy oil represented only 2.2% of total domestic utilization, the lowest percentage in history. Of the soy oil used industrially, 35% was used to make resins and plastics, 23% for paints and varnishes, 11% for fatty acids, and the remaining 31% for other nonfood uses ( Soya Bluebook 1982). In 1982 the American Soybean Association (ASA) was working to encourage the use of soy oil as a pesticide carrier.

In 1980, accounting for 66.5% of all oils and fats consumed in the US and 82% of all vegetable oils, soy oil was clearly America's leading oil.

In 1980 Erickson (of the ASA) and co-workers edited the fist major book devoted solely to soy oil; it was published jointly by the American Soybean Association and the American Oil Chemist's Society. Titled Handbook of Soy Oil Processing and Utilization (598 pp), with chapters written by the top researchers in their fields, it has served as a source of much of the recent nonhistorical information in this chapter. Other recent sources of good information are the proceedings of the various world soybean conferences, listed under "proceedings??" in our Bibliography, plus periodical reports such as the USDA's "Fats & Oils Outlook and Situation Ref??," the Foreign Agricultural Service's "Fats, Oils, and Oilseeds Ref??," and the annual Soya Bluebook , the best single source of statistics on the industry.

Problems with the Meat Centered Diet and Feedlot System . Although the American soybean crop each year produces a vast supply of high-quality, low-cost protein, that can be made into a great variety of tasty, nutritious, and healthful foods, the great majority of this protein ends up in the stomachs of animals, not people. As we saw before, chickens are the biggest animal consumers of this protein, followed by hogs, then cattle. Only about 3% of the US soybean crop is used directly for food in the US. In the decades after 1950, low cost soybean meal fueled the expansion of livestock and poultry feeding, and the growth of the meat-centered diet. (The category "meat" includes poultry.)

Starting in the early 1970s some of the previously unrecognized problems with the meat-centered diet and the feedlot system began to come to the public attention. The problems raised were: the excess consumption of animal fats, proteins, and feed additives caused health problems; the use of soybeans and grains to feed livestock instead of people aggravated world food shortages; the feedlot system caused pollution and was highly wasteful of energy, water, and topsoil; the raising and slaughtering of animals under factory-like conditions was cruel and disrespectful of what some considered basic rights of all living beings. One of the earliest, most carefully documented, and best known of the indictments of the meat-centered diet and feedlot system, and a practical alternative to it, appeared in 1971 in Diet for a Small Planet , by Frances Moore Lappe. By 1982 the book had sold 2 million copies and inspired numerous other studies and publications on the subject.

Let us take a brief look at each of these issues:

Health Problems. By 1981 the annual per capita meat consumption in 23 countries had topped 60 kg (132 pounds) a year. The highest meat consumption was found in the US (112.6 kg/person), Argentina (111.5), Australia (105.6), New Zealand (98.1), Canada (95.6), Uruguay (94.0), and France (92.0) (Crittenden 1981). As noted earlier in Chapter 7, because the bodies of people living in these countries had never been subjected to such high intakes of saturated fats, cholesterol, and animal proteins, a host of degenerative diseases, especially coronary heart disease, cancer, strokes, increased with meat consumption, as did obesity. Many studies (Ref??) showed a close the diet and the diseases to be closely linked. The drive to make animals grow faster led to the use of hormones in livestock rearing, and these were vigorously defended by the industry long after they had been shown to be carcinogenic. When DES (diethylstilbestrol) was finally banned in 1977, livestock feeders lost considerable public confidence. To reduce disease levels in the crowded feedlot conditions, antibiotics were regularly used in the feed, and these appeared in the meat as consumed. (Why a problem??) Pesticide residues sprayed on the feed crops also appeared in the meat and milk. Little is known of the long-range effects of these toxic chemicals on human health.

Until 1976, beef were graded by the USDA in proportion to the amount of fat on their carcass, and grain feeding was the proven way to add lots of fat quickly. Soybeans helped to turn lean range-fed beef into the Prime-grade marbled beef and hogs into fatty slices of bacon--exactly what doctors and nutritionists warned against. Most soybeans, however, were used to produce chickens (which are low in fat and fairly low in cholesterol) and eggs. The 1976 change that allowed slightly leaner beef to qualify as Prime was probably a small step in the right direction. Milk is still priced by its fat content.

What changes in the system were recommended? (By whom??) First, reduced consumption of animal fats and cholesterol and, perhaps in developed countries, of animal protein (Carroll 1978). This can be accomplished by eating less total animal products and by switching to low-fat products such as chicken and nonfat milk. Second, a revamped grading system that placed a premium on low-fat products. And third a more careful monitoring of the use of the levels of hormones, antibiotics, and pesticide residues in animal products. Extensive epidemiological evidence (Figs. 7.?? and ??.??) suggests that in any country, even poor Third World countries, increases in the consumption of animal fats and cholesterol are directly linked at every level to increased rates of coronary heart disease and cancer. Thus the insidious concept of "improving diets" or "upgrading diets" by promoting increased consumption of meat and oils or fats should be discouraged. And, of course, the poor who might possibly benefit from added protein from low-fat meat in their diet, have never been able to afford grain-fed livestock or poultry anyway.


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