Trans Fatty Acids:Advantages and Disadvantages

ما لها وما عليها : األحماض الدهنية المتحولة

By

Dr. Adel Gabr Abdel-RazekNational Research Centre

10 December 2017, Cairo, Egypt.

Introduction

We all need to include some fat in our diets to remain healthy,

• not all fats are equal in terms of their effects on our health.

Some are more beneficial and others may be unhealthy if you eat too

much of them.

Trans fats have received much interest in recent years.

This presentation looks at trans fats, comparing them to other types of fats,

describing which foods they are in and giving you tips on take it or leave it.

• The major isomer in milk fat is cis-9, trans-11 CLA (18:2) represents

about 75-90% of the total CLA in milk fat.

• This is of special importance because the cis-9, trans-11 CLA isomer

has been shown to be anti-carcinogenic in biomedical studies.

• Indeed, utilizing a breast cancer model, a recent study demonstrated

that rats fed a diet containing butter that was naturally enriched with

cis-9, trans-11 CLA had a lower mammary tumor incidence and fewer

tumors than rats consuming the control diet.

• The second most prevalent CLA isomer in milk fat is trans-7, cis-9

and its concentration is about 10% of that for cis-9, trans-11.

• To date, the specific biological effects of trans-7, cis-9 CLA have not

been investigated because of its limited availability.

• In addition, milk fat content of trans-10, cis-12 CLA can be markedly

increased under certain dietary situations, but even in this instance the

amount is less than 2% of the cis-9, trans-11 CLA content.

Double Trouble

Saturation, positional and geometric isomerization

The addition of a hydrogen atom to the carbon–carbon double bond (sometimes referred to as ‘half hydrogenation)

• Free rotation around the carbon-carbon bond axis followed by dissociation of a

hydrogen atom back to the catalyst surface to re-form the carbon–carbon

double bond.

• Because of the free rotation illustrated above, the re-formed double-bond

molecule can be in the cis or trans geometric configuration.

• The geometrically isomerized molecule (trans or cis configuration) can

desorb from the catalyst surface back into the bulk of the oil.

• Addition of a second hydrogen atom to either of the two intermediates illustrated

above to create a saturated carbon-carbon bond (saturation).

• Both reactions give rise to the same saturated moiety and both reactions are

irreversible.

• The saturated molecule then desorbs from the catalyst surface back into the bulk of

the oil.

• Dissociation of a hydrogen atom from a carbon atom adjacent to the site of the first

hydrogen atom addition.

As shown below, this re-forms the carbon–carbon double bond but in a different position

on the carbon chain (positional isomerization).

• The positionally isomerized molecule can then desorb from the catalyst surface back

into the bulk of the oil.

How much Trans Fat Is Recommended?

• Researchers agree that it is important to keep the intake of trans fat to a

minimum.

• In fact, the American Heart Association recommends that consumers limit

the total amount of trans fat and saturated fat combined to less than 10

percent of total calories everyday.

• Just remember, the less trans fat, the better.

• The main dietary source of industrial trans fats are partially hydrogenated vegetable oils. The

World Health Organization argues that the removal of partially hydrogenated vegetable oils

from the food supply would result in substantial health benefits.

• After determining in June 2015 that partially hydrogenated oils (PHOs) were no longer

'generally recognized as safe' for use in human food, the United States FDA requested food

manufacturers to remove them from products by June 2018.

• The European Union does not have legislation regulating the content of trans fats in food

products or requiring their labelling.

• Thus, should a product contain partially hydrogenated oils (and hence, possibly TFAs), its

label will indicate this, but it will not indicate the exact amount of trans fats present.

Hydrogenated Fats

Food Reformulations to Reduce Trans Fatty Acids

• Manufacturers and restaurants aimed to replace the trans fatty

acids in foods (present largely because of the use of partially

hydrogenated oils) with alternative fats.

Choosing solid shortenings for food applications is more complicated

than liquid oils, as the shortening’s structure impacts its function, such

as flaky texture in pastry and smooth mouthfeel in breads.

Solid shortenings range from very hard and highly saturated to very

soft and plastic with a high degree of unsaturation.

• For many years, much of this functionality was achieved through the use of

trans fats.

• Trans fats are unique, in that they are unsaturated lipids that function much like

their saturated counterparts.

• While small amounts of trans fats are naturally occurring in some foods, such as

butter, they primarily are produced through partial hydrogenation of unsaturated

oils, such as soybean oil.

As the food industry rapidly moved away from using trans fats because of perceived

health concerns, lipid scientists had to scramble to find replacements that provided the unique

functionality that trans fats offered.

Palm and palm kernel oils have become the primary

sources for zero-trans alternative shortenings or

margarine.

This is because they have a high degree of shorter-chain saturated fatty acids,

with lower melting points, that can be manipulated to provide crystalline

structure with a range of melt profiles.

So, Formulation of Zero-trans Acid Shortenings

and Margarines and Other Fatty Food

with Products of the Oil Palm, can solve the problem

The move to palm-based shortenings and margarine:

fats and oils manufacturers now have built much of the functionality into

palm-based shortenings, to the point that they are now comparable to their

trans counterparts.

This has been done through fractionation and recombination of the

triglycerides, along with rearrangement of the fatty acids on the

triglyceride molecules.

• While palm-based shortenings now are working well in foods, there

continue to be concerns around their saturated fat content.

Recently, palm-based shortenings are being transformed from

containing as much as 64-69% saturated fat to as low as 24-46%

saturated fat with equal functionality.

This is being done by using unsaturated fractions of soybean and

canola oils in combination with inter esterified palm fats.

Oil palm, is a unique crop as its fruit produces

two distinct types of oils;

Crude palm oil from the mesocarp & Crude palm kernel oil from the kernel.