Reinventing oil science to create baked goods sans trans fats is a rare opportunity for food processors to develop and market nutritionally advanced oils that taste good without harming the heart. Todd Runestad reports
The beginning of the end for trans fats happened in 1990 in the Netherlands. Researchers in a randomised controlled clinical trial of 34 women and 25 men discovered that trans fatty acids were not only as bad as LDL cholesterol-raising saturated fatty acids but actually could be worse because trans fats also lower HDL cholesterol levels.1 The ratio of total to HDL cholesterol is a more specific marker of coronary artery disease than is LDL cholesterol.
In 1992, the Dutch were at it again, comparing the effects of linoleic acid (cis,cis-C18:2(n-6)) and its hydrogenation products elaidic (trans-C18:1(n-9)) and stearic acid (C18:0) on serum lipoprotein levels on healthy adults. In the study, the linoleic diet provided 0.1 per cent of energy as trans fats, compared to 0.3 per cent on stearate and 7.7 per cent on elaidic acid. The results showed a linear dose-response relation wherein trans fats in the diet significantly lowered HDL cholesterol and raised LDL relative to linoleic acid.2
Last year, the original Dutch research group, headed by Ronald Mensink at Maastricht University, conducted a 60-trial meta-analysis to calculate the effects of the amount and type of fat on total:HDL cholesterol. The results demonstrated why trans fat labelling requirements are a good thing: The ratio decreased if cis unsaturated fatty acids replaced saturated fatty acids. What?s more, the effect on total:HDL cholesterol of replacing trans fatty acids with a mix of carbohydrates and cis unsaturated fatty acids was almost twice as large as that of replacing saturated fatty acids.3
Of particular note, oils rich in lauric acid decreased the ratio of total to HDL cholesterol, while myristic and palmitic acids had little effect on the ratio, and stearic acid reduced the ratio slightly. The ultimate conclusion was that coronary artery disease risk is reduced most effectively when trans fatty acids and saturated fatty acids are replaced with cis unsaturated fatty acids. The largest reduction is seen with unhydrogenated oils, such as rapeseed (canola), soybean and olive oils. (See Figure 1, below.) These studies helped change the scientific and regulatory consensus on trans fats over the course of two decades.
Taking trans out
In natural oils, fatty acid double bonds have two hydrogen atoms on one side of a link that repel each other and create a kink in the chain. Chains can have any number of kinks. These are called ?cis? configurations. Hydrogenation chemically alters these double bonds so that the hydrogen atoms are on opposing sides, in a ?trans? configuration, and the chain is straightened out.
Straight molecular chains are more compact than kinked ones, thus creating a more stable whole. Shelf-stable bakery products are one result. Particularly for the baking industry, it is a huge challenge to remove partially hydrogenated oils and maintain the textures and structures needed.
The evolving trans fats story is a rare opportunity for food processors to develop and market nutritionally advanced oils. The key to successful launches is maintaining both hydrogenation?s ability to extend product shelf life by reducing oxidation as well as its superior structural functionality in finished baked goods. At the same time, new oils must eliminate trans fats? untoward cardiovascular health effects. As the cost for these oils is as much as double compared to hydrogenated trans fats, expense is also a consideration.
This is no easy feat with current oils. For instance, monounsaturated oils such as olive oil are just not stable. Polyunsaturated fatty acids are also unstable, which is why hydrogenation and trans fats emerged. Sunflower oil offers a clean taste. Blends using safflower and other oils approach the stability of partially hydrogenated oils.
One start-up, Source Food Technologies based in North Carolina, has taken the work done by Brandeis University in Massachusetts and introduced a tallow base oil that is more stable than vegetable oil and blended with corn oil in order to reduce the cholesterol effects. The key patent is on the proprietary blend of tallow and vegetable oil. The upshot is a decrease in trans fats and less oil absorption of fried foods, which is why it is being marketed primarily to the fast foods and food services sector. Because less oil is absorbed, the oil lasts longer. This factor helps make up for the high initial costs for the oil.
Serendipity is often the handmaiden of science. In the case of California Natural Products, a search for a fat substitute in ice cream paved the way for an all-natural rice syrup solid that provides the functionality of trans fats and can replace 100 per cent of the shortening in baked goods. The rice is similar in size to fat globules, like in ice cream, and has unique carbohydrate structures due to the structure of the rice starch molecule. So it?s a carbohydrate that acts like a fat.
The upshot is that products can have all of their fat removed (or most, anyway; some fat is desirable to maintain positive organoleptic properties), and in the same vein have no trans fat content.
Tropical oils such as palm also provide the body and texture to products such that no further modification of the oil is necessary, resulting in a natural trans-free choice.
Biotech companies have begun commercialising low-linolenic soybeans produced through either genetic modifications or conventional breeding that will reduce or eliminate trans fats in processed soybean oil. When used for frying, low-linolenic oils eliminate the need for partial hydrogenation. Together, soybean oil and palm oil account for over half of all oil consumed in the world.
Companies also are turning to interesterification, in which acids or enzymes modify the fats to make them solid. The term interesterification comes about because the component fatty acids in the oils are combined with other organic groups and so are technically esters; these are shifted about within the oil molecules during the reaction.
In margarines and shortening, hydrogenation hardens oils whereas interesterification blends soft oils with hard fats to a desired functionality and consistency. Palm oil and its hard fraction, stearin, are one option as hard stocks for interesterified goods. Interesterified fats are used in Canadian margarines by interesterifying palm oil and/or palm kernel oil with canola oil.4
The Food and Drug Administration recently issued an important labelling clarification. Interesterified fats containing greater than 20 per cent stearate may be properly labelled as ?interesterified soybean oil,? with the possible additional descriptor of ?high stearate? or ?stearic rich.? This will allow companies to replace the demon term ?hydrogenated? with the term ?interesterified? when describing these ingredients within a finished product?s ingredient declaration. The random or chemical interesterification is the most applied interesterification modification process of oils and fats because it is easier and cheaper compared to directed or enzymatic.
For many manufacturers, a reformulation strategy begins with reinventing the science. You want to achieve similar qualities while maintaining product integrity in terms of texture, structure, taste and shelf-stability. Oil options that also minimise saturated fats need to be identified. In some cases, this means using some ratio of healthier oils; in others, tropical oils.
Even with a clear lack of studies that might show deleterious health effects decades hence, pro-activity is needed. By the same token, it is important to note that fats that are sources of trans fats are also carriers of other dietary unsaturated fatty acids such as oleic, linoleic and linolenic that have good effects on cardiovascular disease risk.
Will these new zero-trans-fat options be healthier? Let?s talk again in a few decades.
1. Mensink RP, Katan MB. Effect of dietary trans fatty acids on high-density and low-density lipoprotein cholesterol levels in healthy subjects. N Engl J Med 1990; 323:439-45.
2. Zock PL, Katan MB. Hydrogenation alternatives: effects of trans fatty acids and stearic acid versus linoleic acid on serum lipids and lipoproteins in humans. J Lipid Res 1992 Mar; 33(3):399-410.
3. Mensink RP, et al. Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serum lipids and apolipoproteins: a meta-analysis of 60 controlled trials. Am J Clin Nutr 2003 May; 77(5):1146-55.
4. Haumann BF. Tools: hydrogenation, interesterification. Inform 1994; 5(6).