What Are Trans Fats

Trans Fats

Trans fats are fats - 'triglycerides' of fatty acids - which contain trans fatty acids. 

These are unsaturated fatty acids that contain at least one double bond in the trans configuration, as opposed to the cis configuration ordinarily found in nature (see chemical formula at the end of this section).

Trans Fats can take two forms:

• Trans fat is produced in the gut of some grazing animals. That’s why small quantities of trans fat can be found in animal products like milk, milk products and meat.

• Trans fat formed during food processing - this type of trans fat is created when hydrogen is added to vegetable oil (a process called hydrogenation) to make it more solid. Partially hydrogenated oils are used by food manufacturers to improve the texture, shelf life and flavor stability of foods. About half of the trans fat British people consume is formed during food processing and partially hydrogenated oils are the main source this type of trans fat in the UK. This form of  trans fats can be found in processed foods such as biscuits and cakes.

The main source of these synthetic trans fatty acids is hydrogenation - an industrial process in which oil is heated to a high temperature (typically 260-270ºC) under pressure and in the presence of a metal catalyst such as nickel, Rayner's nickel (a nickel / aluminium alloy) platinum, palladium or cobalt, then hydrogen is introduced. The hydrogen is absorbed into the fat molecules, changing its molecular structure and its chemical composition as it converts the unsaturated oil to a more saturated form.

This transforms the oil, naturally liquid at room temperature, into a hard or semi-hard grey-white fatty substance. This "partially hydrogenated vegetable oil" is virtually flavourless and has excellent keeping properties, making it an ideal for the food industry.


They key is that Trans fats extend the shelf life of food.  They also add a certain pleasing mouth feel to a whole range of processed foods.  Think of the buttery taste of popcorn or crackers, crispy french fries, frosting, pies and pastries. To a certain extent these foods taste good due to trans fats! 

Trans Fat Chemical Formula

Where’s the Trans Fat? Trans fat can be found in many of the same foods as saturated fat. These can include: Crackers, cookies, cakes, frozen pies and other baked goods Snack foods (such as microwave popcorn) Frozen pizza Fast food Vegetable shortenings and margarine Refrigerated dough products (such as biscuits and cinnamon rolls) Ready-to-use frostings

Trans Fat history

The hydrogenation process was patented in 1903 in the US by chemist William Normann.

Commercial production of hydrogenated oils and fats began soon after by Procter & Gamble (P&G). 

In 1911 P&G, noticing that the hydrogenated oil looked and behaved like lard, began to sell it as a lard substitute under the brand name of Crisco.

Hydrogenated fats became more established in the 1930s, due to their lower cost. Their use rapidly increased during World War II when people turned to margarine and vegetable shortenings as alternatives to butter, which was subject to rationing.

They received a further boost in the late 1980s as health concern focused on saturated fats, which were widely vilified as extremely unhealthy. Meanwhile margarines containing hydrogenated vegetable oils were promoted to consumers as a 'healthier' alternative, replacing butter and other animal fats, as well as more saturated tropical vegetable oils such as palm and coconut.

Another factor was the growth of vegetarianism: manufacturers of biscuits, for example, were worried about loss of market share as vegetarians avoided products which contained "animal fat" as shown in the ingredients list.

It has since become clear that even the more saturated vegetable and animal fats are far healthier than hydrogenated fat containing trans fats.

In the 1980s the food industry began to selectively hydrogenate oils to produce a high volume of 'elaidic acid', . This is because elaidic acid melts at mouth temperature, giving a luxurious sensation in the mouth, which when added to food, improves its taste.