Sorting Fat from Fiction
First, there was the transition from animal-based to plant-based oils and fats. Next, it was the reduction of tropical oils such as palm, palm kernel and coconut to reduce the level of saturated fats. Now, the trend is to remove or reduce the level of trans fatty acids. Trans fatty acids occur naturally in products such as meat, dairy and some baked goods; but, hydrogenated oils contribute the majority of trans fatty acids to our diet.
Partial hydrogenation originally was developed to improve oil stability and change liquid oils into semi-solids so that fats and oils could be used over a broader range of applications. As the understanding of the medical implications of trans fats evolves, what does it mean to those who develop food products?
What About Trans Fatty Acids?
Consumers are being educated by organizations such as the American Heart Association, Dallas, Texas, to select products containing more non-hydrogenated oils and less saturated fats. In the dilemma of “butter vs. margarine,” camps are split as to which is the “lesser of the two evils.” A study in the December 6, 2000 issue of the Journal of the American Medical Association indicated that “margarine is a more heart-healthy choice than butter.” Margarine contains no dietary cholesterol but does contain trans fatty acids.
In 1999, as a result of studies reporting the tendency of trans fatty acids to raise total blood cholesterol levels, the FDA proposed to amend its regulations on nutrition labeling to require that the trans fatty acids levels in a food be included in the amount and percent Daily Value declared for saturated fatty acids. Some reports also indicated that trans fatty acids tended both to raise LDL-cholesterol levels and lower HDL-cholesterol levels. A more recent study conducted by the Institute of Medicine, Washington, D.C., concluded there is no safe level for trans fatty acids so it would not specify an upper limit.
The FDA recently announced that a final rule requiring that the amount of trans fatty acids in foods be listed on labels is pending. This ruling could be finalized by as early as this fall or early next spring. Food producers will be required to list the grams of trans fat on a separate line in the nutrition facts on labels, but trans fats will not be included in the Percent Daily Value. Because trans fat occurs naturally in meat, dairy, baked goods and other products, a total elimination would require such a drastic change in consumers' diets that other health issues may emerge as a result. Thus, the recommendation from the Institute of Medicine's report is to be “as low as possible while consuming a nutritionally adequate diet.”
Fats and oils are not immune to the functional food trend. Designer lipids and modified fats and oils are being assessed for their ability to impart health-promoting benefits. Perhaps the term “healthful lipids” would be more appropriate and consumer-friendly in terms of promoting the virtues of fats and oils.
An emerging trend in fats and oils is in the area of long chain polyunsaturated fatty acids such as certain fatty acids of the omega-3 and -6 families, and conjugated linoleic acid (CLA). The difficulty of fortifying products with these ingredients, or any nutritional ingredient, is highly dependent on the level needed to reach any claim that the food producer hopes to advertise.
Highly unsaturated fatty acids in their liquid form, currently, are less feasible due to their limited shelf life. Some suppliers offer many of these lipids in a highly concentrated powder form that makes them easy to add to food products. Other advice previously noted in PF includes use of adequate packaging and adding the easily-oxidized fats toward the end of processing, to minimize exposure to heat, light and air.
Impact on Formulations
From a product development standpoint, changing the composition of a fat or oil can be as difficult as replacing or reducing a product's fat level. If only minor alterations are required, such as when small quantities of highly concentrated lipids (e.g., omega-3 fatty acids) are added to enhance the nutritional quality of a food product, complications may be fewer than reformulating due to changes in fat quantity or type. (See sidebar.) In contrast, when major changes in fat sources or composition become necessary, the magnitude of difficulty can be similar to that presented by fat replacement and reduction efforts.
When fat reduction efforts were at their peak, the primary formulation tools available for developers were to: 1) replace the lost attributes of mouthfeel and moistness imparted by fats, 2) manage the extra moisture that was usually added and 3) mimic the functional and structural elements provided by the replaced fat. By contrast, replacing or reducing the quantity of specific components of fats may require new oil sources or blending fully saturated fats with unsaturated, non-hydrogenated oils. Development of specialty fats or biotechnological advances also is necessary, since many of the methods utilized to reduce trans fatty acids can increase the level of saturated fatty acids.
What does this mean for research and development scientists? Much of their fate appears to lie with companies producing shortenings and oils. Patents obtained since 1999 focus on the replacement or reduction of trans fatty acids for use in margarines and spreads. Esterification methods and transgenic plants have been used to reduce the need for hydrogenation. Interesterification permits “tailoring” of triglycerides to produce specialty fats with very specific melting point ranges. Unfortunately, these processes tend to increase the amount of saturated fat by utilizing palm and palm kernel fractions or by increasing the amount of palmitic acid in the case of the transgenic corn oil.
Suppliers have noted that there are several factors that have limited the application of many of these methods. According to the Institute of Shortening and Edible Oils, Washington D.C., “functionality, technology, availability, economics and strength of scientific evidence” are among the reasons that the introduction of low or no trans fat alternatives have been limited. The National Center for Agricultural Utilization Research (NCAUR) in Peoria, Ill., developed a low-trans hydrogenation method and claims it can make a product with less than 10% trans fatty acid content, suitable for use in margarine and other spreads.
Blending tropical oils—such as palm and palm kernel—with liquid oils is not an ideal option since it increases saturated fatty acid amounts. The original FDA proposal on trans fat rules indicated that claims of “trans fat free” would require the product to have less than 0.5 grams of trans fat and less than 0.5 grams of saturated fat per serving.
Fat Replacement in a Different Sense
Do consumers, who are advised to reduce the amount of trans fatty acids in their diet, expect food products to contain no trans or reduced trans fatty acids? The difficulty of replacing solid, hydrogenated or partially hydrogenated fats with liquid, non-hydrogenated, oils will depend on the application.
Applications requiring shortenings or partially hydrogenated oils rely on the solids content, polymorphism and melting point profiles for formation and stability of the final product. Melting point profiles are affected by fatty acid chain length, degree of saturation, types of fatty acids and isomerization. It is these isomers present (including trans) in vegetable shortenings and margarines that are responsible for the semi-solid state of these products.
Applications where the rate and type of crystallization of the fat is imperative for product performance and stability will be extremely difficult to manage using liquid oil as a replacement (margarines and spreads, chocolate and RTS frosting). Polymorphism of fat is dependent on molecular structure, crystallization conditions, temperature and storage conditions.
A one-to-one replacement of a hydrogenated shortening in a baked good with a liquid oil usually does not work in instances where 1) the fat content is high and 2) the solid fat is critical to maintain structure at certain points in the process or is the required form upon cooling. Examples of this are puff pastry and laminated baked goods. These products rely on shortenings formulated to melt at a very specific point during the baking process and would be greatly affected by a change in composition. Oils and shortenings used to fry doughnuts or french fries must contain enough solids to “set up” upon cooling so sugar can adhere to doughnuts and the products do not leave oil slicks on plates or in containers. The key will be how well the oil processors can customize and blend to obtain similar functionality with different precursors than before; although, as soon as customization is discussed, price will inevitably increase.
Since hydrogenation is used to help foods stay fresh on the shelf and/or to obtain a solid fat product, reformulating products that are supposed to be shelf stable will be a challenge. With the increasing number of products developed to withstand longer shelf lives, a change in fat and oil composition that would decrease the shelf life goes against this trend and may force some products back to the refrigerated or frozen distribution channels.
Until adequate substitutions are available, many products may require re-development, defined as a combination of reformulation and processing changes. For example, emulsifier systems may need to be re-balanced or modified, depending on the changes in the fat composition necessary to reduce or eliminate the need for hydrogenation. When fat replacer ingredient “systems” were introduced, many were not easily implemented because they required additional equipment such as shearing devices or other pre-processing requirements to use them.
With low- and no-fat products, consumers have become accustomed to a certain reduction in eating quality associated with many—but not all—of these products. It will be interesting to see how consumers react when trans fats are labeled and additional health claims for various healthy lipids appear in the future. Ultimately, this will drive the development process, but the timing of these products will be dependent on the availability of suitable replacements.
During the most recent IFT meeting in Anaheim, Calif., one supplier indicated that the company is commercially “ready” with a reduced trans all-purpose shortening. This supplier indicated the reduced-trans product contains an 80% reduction in trans fatty acids when compared to other shortenings and can be used as a drop-in replacement. Applications work conducted internally potentially minimizes reformulation efforts for cookies, biscuits, pie crust, cakes and icings. Other suppliers indicate their liquid shortening products have reduced trans options but that they are still working on trans reduction in solid shortenings.
The challenge is to reduce the level of trans fatty acids without increasing the saturated fatty acid levels. Product developers may find they require further assistance with ingredients and technologies from specialty fat suppliers and non-fat ingredient manufacturers.
U.K.'s Institute of Food Science & Technology page on trans fats
University of Delaware searchable database of trans fat content of foods
International Food Information Council Foundation (IFIC) Q&A
Links to oil organizations, government statistics and research organizations
Institute of Shortening and Edible Oils
Use “trans fats” or “trans fatty acids” in keyword search field
FDA's 1999 proposed trans fat labeling
American Heart Assoc. page on trans fats