Replacing TAGS with DAGS
Since January 2006, when the US Food & Drug Administration (FDA) requirement for labelling the trans fats content of food products came into force, there has been a remarkable transformation in the edible oil consumption of Americans. Once it became legally necessary to label for them, food companies did not want to include trans fats on their labels, and so most have opted to eliminate or at least drastically reduce the trans fat content of their products.
Trans fats and hydrogenation are now dirty words in the US. Trans fatty acids are not present in most vegetable oils but are formed during partial hydrogenation (to harden oils into fats, or to make them more stable in use) and other high temperature refining operations. Research has shown that the trans fats formed in this way not only raise LDL 'bad' cholesterol but also lower HDL 'good' cholesterol, and so have been judged to have even worse effects on health than saturated fats.
Soybean oil - classified as semi-drying oil by the paint and varnish industry - had been the major edible oil in the American diet for decades and was used in everything from salad dressings and frying oils to vegetable lard. Since the typical soybean yields an oil containing about 7% linolenic acid (the predominant fatty acid in linseed oil), stable salad oils and frying oils were only achievable by partial hydrogenation, the process that gives rise to the trans fats.
Today, use of soybean oil by the food industry is in the doldrums and US consumption of sunflower, rapeseed (canola) and olive oil has been growing as never before, thanks to huge media interest in the trans fat issue. Indeed, last October the FDA granted a qualified health claim for canola (rapeseed) oil, which is now being grown in increasing volumes in the US.
PALM OIL TO THE RESCUE
Fast food chains - as well as a growing number of towns and cities, and even one state - are now committed to the virtual elimination of hydrogenated and trans fats from the American diet. While 20 years ago the soybean lobby campaigned against tropical oils in the US as being bad for the diet, palm oil in particular has proved to be the saviour that makes non-hydrogenated, zero trans semi-solid and hard fats possible, and so imports have soared.
Needless to say, at least two types of low-linolenic, high-oleic soyabean varieties are now in commercial production, as well as high-stability canola and sunflower oils that can be used for frying without hydrogenation, but it will be some years before the various new soy varieties can be grown in sufficient volume to replace the traditional soy crop completely, and some have been developed using genetic modification.
The US moves have caused a corresponding reaction on the other side of the Atlantic. In the UK, retailers such as Tesco and Marks & Spencer have pledged hydrogenation-free own-label products.
In Europe, however - where the definitive research into the effects of trans fats was done in the 1990s - the picture is starkly different. Collectively, the nations of northern Europe have traditionally grown and imported a wide range of edible oils - including tropical oils - for domestic use, and soybeans have only ever been grown on a limited scale in southern Europe.
European fats expertise has also been central to the early development of Malaysia's palm oil industry; and it is palm oil - which can be fractionated into a range of products without hydrogenation - that is the basis for (non-hydrogenated) zero-trans oils and fats with a vast range of functionalities.
Consequently, there have been no trans fats in tub margarines in the EU for more than a decade, and no consumer in Europe would ever knowingly have put partially hydrogenated soybean oil on a salad! In Europe, therefore, any remaining hydrogenation issues are largely limited to bakery fats and confectionery fats, where very specific melting characteristics are needed to arrive at products that consumers cannot resist.
While trans fats made by hydrogenating vegetable oils are a relatively modern phenomenon, humans have been consuming other trans fats - made by microbial hydrogenation - in the milk and body fats of ruminant animals for thousands of years. And the most prominent one of these is conjugated linoleic acid (CLA), now well known for health benefits that include anti-cancer and weight reduction properties.
The CLA marketed by Cognis and Lipid Nutrition is in fact made from safflower oil - using an extraction process that the producers say does not involve hydrogenation - and contains both the cis9, trans11 isomer and a trans10, cis12 isomer said to be important in the promotion of muscle growth at the expense of body fat.
FAT REDUCTION WITH DIGLYCERIDES
Obesity control is also behind the development of a special structured lipid - made from vegetable oil and used like vegetable oil - by Kao Corp in Japan. Said to be digested differently than ordinary oils and fats and now in full scale commercial use in Japan for several years (as Econa), this diacylglyceride (DAG) oil is the subject of a joint venture between Kao and Archer Daniels Midland in other parts of the world, where it is sold as Enova.
Enova, which is made from rapeseed and soybean oils and had been awaiting approval for use as a food oil in the EU for three years, finally gained approval last year.
Paradoxically, however, it contains trans fats, and its approval by the EU's standing committee last year was dependent on its trans fat content being reduced from 2% to 1%.
But the question arises as to why trans fats have been an issue at all in the approval process, since - by all accounts - DAG products do not necessarily contain trans fats at all.
"When making DAG products, you can choose a processing method and base oils to ensure that trans fats are practically eliminated," says Dr Neil Hargreaves at Leatherhead Food International (LFI). Hargreaves and colleagues at LFI are proposing to carry out an
industrially-sponsored collaborative project to investigate the potential use of DAG products to partially or fully replace saturated fats in food products.
Dr Hargreaves explains that DAGs - diacylglycerols or diacylglycerides - are a generic range of products, of which the branded Enova oil is only one.
The term DAG refers to their molecular structure, where they differ from normal fats and oils (triacylglyerols or triacylglycerides, TAGs) by having one less fatty acid chain per molecule.
They are found naturally in vegetable oils but only in small proportions.
Sometimes called structured lipids, DAGs can be made by splitting oils and fats into their constituent fatty acids and glycerine and then recombining these in a controlled way, so that the final molecule contains a glycerine backbone attached to only two fatty acid groups instead of three.
Surprisingly, DAGs are more solid than their TAG relatives, typically having melting points about 10 degrees
higher.
More importantly, the most stable and highest melting isomers in this family (the 1.3 isomers) are metabolised in a different way to conventional fats and oils (TAGs), so they are not available for fat deposition in the body and therefore have potential benefits in obesity reduction.
LIQUID AT AMBIENT TEMPERATURE
Enova is made from unsaturated fatty acids and is liquid at ambient temperature. It behaves like cooking oil throughout the temperature range and can therefore be used for a range of culinary applications including frying.
By contrast, LFI's research will focus on a range of saturated DAG fats that have the potential to replace conventional saturated (TAG) fats in blends that can be solid at room temperature and can even have the sharp melting characteristics of cocoa butter and similar melt-in-the-mouth fats.
Potential uses for such a family of DAGs would include various bakery and confectionery applications and even biscuit fillings.
"Replacing saturated TAGs with DAGs," says Neil Hargreaves, "can achieve a double benefit on the health front. You use a lower level of saturated fats (TAGs) for a specific hardness and there is also the obesity reduction factor."
RESEARCH NEEDED
As he points out, all the research into DAGs that has been done to date - most of it in Japan - has looked only at liquid DAG products so there is a need to focus on the rest of this large family.
"We need to get a detailed understanding of the melting and crystallisation properties of saturated DAGs and the blends of them that will achieve specific functionalities in foods."
Such detailed knowledge is very scarce at present. To date, the food industry has mainly used DAGs as emulsifiers, at low levels of inclusion in the 2% to 3% range, and often in blends with monoglycerides, but not as replacements for functional fats.
LFI's two-phase collaborative study project is expected to take around 12 months to complete once it has been started - and the start-up depends on gaining sufficient interest and support from industry.
