June 1, 2000
Fats and Oils 2000:
By: Bob Wainwright
Fat is currently a high-visibility nutrient for a number of reasons. First, there's the recent proposal for trans-fatty acid labeling. Secondly, fats and oils are in the center of the very emotional biotechnology debate. Also, there's great interest in minor lipid components, particularly phytosterols, that exhibit particular biological influences and which have recently begun to find their way into the marketplace as functional food ingredients.
The trans challenge
Recent clinical studies have shown an association between dietary trans-fatty acids (TFAs) and elevated levels of total cholesterol and low-density lipoprotein (LDL) cholesterol, and unchanged or reduced high-density lipoprotein (HDL) cholesterol relative to control diets. trans intakes during these studies ranged from 4% to 11% of total energy.
What constitutes "average" intake of TFA has in fact been debated. David Allison et al report in the February 1999 issue of the Journal of the American Dietetic Association that "on average, the U.S. population consumes a mean of 5.3 grams trans fatty acids per day - about 2.6% of their total energy and 7.4% of their fat energy." According to the scientists, this research also confirms earlier findings indicating that saturated fatty-acid (SFA) intake remains high, and at 12.5% of total energy, is of greater concern, relatively speaking, than trans intake.
It's important to note that the majority of trans isomers formed during partial hydrogenation of vegetable oils and fats are in different positions along the fatty-acid backbone (primarily elaidic) than those that occur naturally in animal fats (vaccenic). Fats from ruminants reportedly account for 20% to 25% of TFA intake. However, trans fats from animal and vegetable sources may present different associations with risk factors for heart disease. Many nutritionists caution against replacing TFAs in the diet with saturates. Rather, the American Heart Association recommends that "naturally occurring unhydrogenated oil be used when possible and attempts made to substitute unhydrogenated oil for hydrogenated or saturated fat in processed foods. Additionally, the recommendation to substitute softer for harder margarines and cooking fats seems justified."
The TNO Nutrition and Food Research Institute, the Netherlands, recently published a study in the European Journal of Clinical Nutrition wherein it concluded: "At the current European intake levels of trans fatty acids, trans fatty acids are not associated with an unfavorable serum-lipid profile. From this and other studies the conclusion can be drawn that for reduction of cholesterol levels the focus should be not exclusively on the reduction of TFA, but on the reduction of all cholesterol-increasing fats, including saturated fatty acid." For perspective, this study found that the average TFA intake for the involved European countries is about half that reported for the United States.
The FDA currently only requires total fat and saturated fat content on the Nutrition Facts label. However, on November 17, 1999, the agency, in response to a Citizen's Petition filed by the Washington, D.C.-based Center for Science in the Public Interest, published a proposed rule "to amend its regulations on nutrition labeling to require that the amount of trans fatty acids present in a food, including dietary supplements, be included in the amount and percent Daily Value declared for saturated fatty acids."
The initial comment period was extended to April 15, 2000, and if the proposed regulations are finalized prior to the end of 2000, labels must be in compliance by January 1, 2002. (If not finalized by the end of 2000, the uniform compliance date rolls forward to January 1, 2004.)
The crux of this proposal is the treatment of TFAs as equivalent to SFAs. In the FDA's eyes, scientific evidence supports the notion that TFAs behave similarly to SFAs in terms of impact on serum-cholesterol levels, and as such, should appear on the Nutrition Facts label. The agency considered 14 intervention studies published between 1990 and 1999 and eight observational studies published between 1992 and 1997 in making its determination. In addition, the FDA took note of trans-content proposals and recommendations by a joint Food and Agriculture Organization/World Health Organization consultation in 1993, the U.K. Department of Health in 1994 and the Canadian government in 1996.
The FDA proposes including TFAs in the saturated fatty acid line of the Nutrition Facts panel by asterisking the total and reporting grams of TFAs at the bottom of the panel. Health claims would not be permitted for foods containing more than 4 grams combined of saturated fat and trans fat per serving. The agency also proposes trans limits in products making nutrient content claims:
TFAs have been called "phantom fats," especially by the popular press, and this is perhaps not completely inaccurate. Some argue that total fat on the Nutrition Facts panel already reflects TFAs. However, the simple label version makes it impossible to derive trans content by comparing total fat against saturated fat, because the balance would be a combination of unsaturated fatty acids, both cis and trans. On the other hand, the more complete label, on which both monounsaturates and polyunsaturates are stated, permits derivation of trans content by simple subtraction. Unfortunately, a great many foods carry only the simple format.
Analytical methodology for TFA determination, both infrared (IR) and capillary gas chromatography (GC), are discussed in the proposed ruling. American Oil Chemists' Society (AOCS) Recommended Practice Cd 14d-96 and AOCS Official Method Ce 1f-96 are the methods of choice for IR and GC respectively. These methods have been collaboratively studied only for fats and oils, not for complex matrices such as multi-component foods. IR is suitable for quantitations down to about 1% trans as a percentage of total fat; GC can provide higher resolution.
The FDA's proposal has fueled a good deal of debate. In terms of a chemical definition, the proposal is inaccurate and inconsistent with other fat-related items on the Nutrition Facts panel. The FDA defines saturated fat content as the sum of all fatty acids with no double bonds. No distinction is made for a particular chain length's propensity to impact serum cholesterol - i.e., a chemical, rather than nutritional definition has been applied.
Similarly, precise chemical definitions were developed for monounsaturated (the sum of cis-fatty acids with one double bond) and polyunsaturated (the sum of cis-cis methylene-interrupted double bonds) fatty acids. Melding TFAs into the saturate category is likely to create even more confusion for concerned consumers.
The FDA's motive is understandable, but will certainly receive much comment from industry, special-interest groups and consumers. The agency's obligation is to identify and limit fat that might increase serum cholesterol, especially LDL, levels. It's generally well accepted that saturates influence LDL levels; the challenge for the agency is to avoid trans-labeling approaches that dilute vital saturate information. After all, average intake of saturates exceeds that of TFAs by nearly five times.
Consumers have a great deal of confusion about the term "partially hydrogenated," fueled in part by the media. The message that has been sent is that the terms "partially hydrogenated" and "hydrogenated" are synonymous with trans; i.e., either term identifies a food as a source of TFAs.
This is often true; however, sometimes it is absolutely false. Recently this misunderstanding has brought undeserved negative attention to peanut butter and related products. Well-intentioned but misinformed nutritionists and others point to peanut butter as an example of a "phantom-fat-containing" food found on nearly every U.S. pantry shelf - but these products are in fact essentially devoid of TFAs.
Understanding hydrogenation isn't all that simple though, because the descriptors "hydrogenated" and "partially hydrogenated" have no clear legal definition. Let's take a look at 21 CFR:
Informal definitions often use the phrase "partially hydrogenated" to define products that are flowable at room temperature, while the term "hydrogenated" applies to fats that do not flow at this temperature. Given these definitions, one can readily appreciate that for most products the terms hydrogenated and partially hydrogenated are subjective, and not uniformly applied across the industry. Ingredient legends do not provide substantial insight into how thoroughly a component has been hydrogenated. Completely hydrogenated oils and fats are devoid of trans and those with only very slight hydrogenation are generally quite lean in TFA content. But the average consumer will find it difficult to guess the trans content based solely on current label information.
Hydrogenation in action
Simply put, hydrogenation adds hydrogen atoms across the double bonds in unsaturated fatty acids. This reaction is extremely important to the food industry because it tailors oils' and fats' stability and melting properties, and hence functionality, to the end application. Process variables are manipulated to arrive at the desired functional parameters; the hydrogenation reaction can be terminated anytime prior to complete saturation.
Many oils and fats are subjected to partial hydrogenation to impart the required functionality and shelf life. The industry has been working diligently to continually improve the nutritional profiles of products in an effort to satisfy market demands. For example:
Beyond these improvements, a variety of options exist for those situations where further change is deemed appropriate. However, in general, the penalty is higher saturates and increased ingredient costs. The former is especially apparent in applications that require fat to convey structure and body. The higher-melting saturates and geometric isomers are largely responsible for contributing structure. Thus, reduction in either category necessitates an increase in the other to maintain texture, or the resultant triglyceride families will soften. Options include the following:
Most of the foregoing options involve higher-cost precursors and/or additional processing, and consequently typically represent higher-cost alternatives. Preserving performance for more-demanding applications also presents a challenge. Therefore, it's prudent to consider serving size when undertaking reformulation efforts to accurately quantify the magnitude of change required and to appreciate the implications for the nutritional panel.
The challenge laid upon food product developers is overcoming the apparent dichotomy represented by the responsibility to achieve the nutritional improvements specified in the FDA's proposed rule vs. the responsibility of delivering products to the marketplace that will generate a return for the company.
The gene pool
Selective-breeding techniques have been practiced for thousands of years in an effort to enhance pest and disease resistance, yield, flavor and a variety of other parameters. For example, some 8,000 years ago, Native Americans domesticated teosinte (a tall, corn-like fodder grass). By crossing mutants exhibiting desirable properties, they developed the corn that Christopher Columbus encountered when he landed in the New World. Over the years, thousands of back-crossings have led to the varieties we recognize today.
However, this process is quite time consuming and rather non-specific. Selectively combining and expressing desirable traits from two species is often impossible, if not extremely unpredictable. The classic example is the Russian breeder who in the 1920s crossed radish with cabbage in an effort to combine the best of both crops - edible radish root and cabbage leaves. Much to his dismay, he ended up with radish leaves and cabbage roots.
By the 1970s, molecular biology allowed the transfer of genetic material between distantly related organisms. Today, biotechnology benefits from the ability to transfer genes across kingdoms (recombinant DNA techniques), thus permitting breeders to precisely target and rapidly achieve objectives. The Economic Research Service (ERS) of the USDA published definitions for a number of terms used to describe modern agriculture:
As stated in its 1992 policy, the FDA expects developers to consult with the agency on safety and regulatory questions related to foods derived from new plant varieties developed through rDNA technology. Since 1994, 24 consultations concerning genetic enhancements to oilseed crops have been completed, but may have pending regulatory issues with APHIS or the EPA.
USDA-APHIS oversees and regulates certain environmental issues such as transgene escape and spread thorough pollen or other vectors, while the EPA regulates the ecological consequences of genes that encode for pesticides. Not all approved varieties have yet been commercialized. The majority are input (e.g., herbicide or pest resistance) traits rather than output traits, and thus have been relatively transparent to the consumer in terms of visible benefits. These have been generally embraced by farmers, but anti-biotech sentiment has apparently started to pressure growers to reduce the amount of genetically modified (GM) crops planted.
The ERS reports that the market demand for nonbiotech corn and soybeans accounted for only 1% and 2% respectively of 1999 U.S. production. However, this report also cautions that despite this small market share, demand is potentially quite volatile and could quickly and significantly increase. It's unclear how the recently proposed policy change will affect demand (see this month's News section for more information.) This volatility is even more evident when taking into account the global position of GM products. For example, European Community (EC) regulations for food and food ingredients that are produced, in whole or in part, from genetically modified soy or corn were revised again in January. The labeling exemption for additives and flavorings that contain components derived from GM crops were revoked; hence, lecithin in chocolate, for example, is no longer exempted. In addition to the EC, Japan, South Korea, Thailand, Indonesia, Hong Kong, Australia and New Zealand are also reported to be in the process of drafting labeling regulations.
On March 7 of this year, the USDA announced a proposal for regulating organic production that includes a provision prohibiting genetic engineering or genetic modification. Although only a very small portion of the top U.S. field crops were grown under certified organic farming systems in 1997, this sector may have an increasingly evident effect on biotech status, especially considering a recently published ERS survey showing that organic farming is one of the fastest-growing segments of U.S. agriculture.
New output traits are coming to market that broaden the palette of lipids available to product developers. These enhancements are targeted toward functionality, nutrition and oxidative stability. Such improvements can be translated by food technologists into improved nutritional profiles.
Biotechnology, both hybridization and genetic modification, has produced a variety of property-enhanced oilseeds in recent years. The objective of many of these programs is to reduce polyunsaturates, thereby significantly enhancing oxidative stability.
Noteworthy commercial introductions include high-oleic (HO) sunflower, canola and soybean varieties. The following stabilities (as determined by Oil Stability Index at 110°C) have been reported for the following oils: traditional soybean, 6.9; HO sunflower, 18.2; HO canola, 20.9; and HO soybean, 80.7.
Low-linolenic soybean oil (less than 3% linolenic acid) and low-saturate soybean oil (less than 8% saturates) are in early stages of commercialization. The challenge is to satisfy the market for which these oils are uniquely suited at a price acceptable to the consumer. Often, the demand for these enhanced oils is meager initially, and thus it's difficult to process them within an identity-preservation environment at a reasonable cost.
Mid-oleic sunflower oil was born two years ago from work conducted at the USDA-ARS Northern Crop Science Laboratory in Fargo, ND. Cultivars capable of producing an oil with 20% less saturates, 50% less polyunsaturates and three times the oleic content of traditional sunflower oil were developed via traditional hybridization techniques. The National Sunflower Association (NSA), Bismarck, ND, obtained rights to this product and is promoting it as NuSun™. This oil is quite stable, and is well-suited to commercial deep-fat-frying applications. The NSA's goal is to ultimately convert the entire traditional (high-linoleic) sunflower crop to the mid-oleic variety. For the 1998 to 1999 crop year, 50 million lbs. of the total 1.8 billion lbs. of sunflower oil produced were mid-oleic. This is expected to grow to 275 million lbs. this year and 770 million lbs. the following year as traditional high-linoleic acreage is converted.
Soybean breeding conducted at the USDA-ARS research center in Raleigh, NC has culminated in the development of a high oil-yielding, low-linolenic (about half that of normal soybean oil), non-transgenically modified product called Soyola. This product was recently released to growers in the southern United States, and represents the first product introduction from the United Soybean Board's 1998 Better Bean Initiative. A high-priority target for this program is development of a low-linolenic, low-palmitic, mid-oleic oil.
The ability of phytosterols to reduce serum cholesterol by inhibiting its absorption from the intestines began to surface in a number of studies carried out from the 1950s to 1970s. These data suggested that vegetable oils, soy sterols and beta-sitosterol are hypocholesterolemic agents. Work conducted in subsequent decades identified the unsaponifiable (sterol) fraction as an important component of this reduction phenomenon. Plant sterols - beta-sitosterol, campesterol and stigmasterol are the most common - closely resemble the structure of cholesterol, but have an extra methyl or ethyl group on their side chain.
According to the USDA, the following phytosterol levels (mg/100 grams) have been reported for refined vegetable oils: peanut oil, 207; olive oil, 221; soybean oil, 250; cottonseed oil, 324; safflower oil, 444; sesame oil, 865; corn oil, 968; rice-bran oil, 1,190. Corn oil is the only product that contains a natural mixture of free phytosterol, phytosterol esters and phytostanol esters. Tall oil, a byproduct of wood pulping, is another good phytosterol source, with phytosterols and phytostanols (saturated sterols) at a ratio of about four to one.
Plant sterols seem more effective at serum-cholesterol reduction when admixed with fat rather than when used neat. Free sterols, however, have a very low solubility in fat, and hence cannot be delivered in appreciable amounts via food matrices such as margarine, table spreads, mayonnaise or dressings. This shortcoming has been circumvented by converting the free sterols into fatty-acid esters.
A number of studies have shown that the saturated form of sitosterol, sitostanol, is virtually unabsorbed, and hence even more effective in terms of cholesterol-uptake prevention. However, a 1998 clinical trial comparing the cholesterol-lowering ability of phytostanol fatty-acyl ester margarine with physterol fatty-acyl ester margarine showed that the sterol esters were as effective as the stanol esters.
Phytosterols aren't the only plant-derived oil compounds being investigated for their health properties, however. Generally, tocopherols - but not necessarily tocotrienols - are synonymous with the vitamin E present in various vegetable oils. In addition to the more widely known tocopherol isomers, four tocotrienols exhibit vitamin E activity. The tocotrienol series has three double bonds in its isoprenoid side chain. The richest natural tocotrienol sources are palm oil (crude palm oil contains 800 to 1,500 ppm), rice-bran oil and barley. Tocotrienols have been found to be effective cholesterol-reducing agents, antioxidants, platelet-aggregation inhibitors and tumor suppressors in animal models.
Given the broad and far-reaching results of the current trans research, biotech developments and new-ingredient progress, it's no wonder that fats and oils are the focus of so much attention. As with most complex issues, there's both upsides and downsides, so it's up to the industry to take the challenges in stride while making the most of all the available opportunities.
Bob Wainwright is manager, technical sales, for C+T Refinery, LLC, Charlotte, NC. After receiving his B.S. in food technology from Ohio State University, he has maintained a presence in the edible-oils industry for over 25 years.
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