A Lesson in FAT
Individual fatty acids can be either saturated or unsaturated and the latter being further sub divided into mono and polyunsaturated. All oils contain a proportion of all three types and it is this combination in any one oil which determines whether it will be a solid fat or liquid oil at ambient temperature. The functionality of liquid oils and solid fats varies considerably and which to choose will depend on the intended application.
Generally speaking, oils containing a greater proportion of unsaturated fatty acids are liquid at room temperature whereas those with higher amounts of saturated fatty acids will be solid
a) Saturated Fats
Certain fatty acids are already ‘naturally saturated’ in that they cannot be made ‘harder’ than they are in nature. As previously noted, the levels of saturates is generally higher in those fats which are solid at ambient temperatures.
Saturated fatty acids are extremely stable i.e. they do not easily become rancid, meaning they have good keeping properties (shelf life). However, Government recommendations advise consumers to limit their intake of saturated fats as they can increase blood cholesterol levels, one of the major factors in heart disease.
Most animal fats such as meat, butter, cheese and cream contain relatively high levels of saturated fat and as such should be eaten in moderation. Many baked goods such as cakes, biscuits and pastries can also be high in saturated fat.
b) Unsaturated Fats
There are three types of unsaturated fatty acids:-
1.Monounsaturated Fatty Acids (MUFA)
Fatty acids in this category have what is known as one double bond in their chemical make up. They are relatively stable to oxidation and the development of rancidity and are now considered, in nutritional terms, as being the best type of fat to eat.
The most common source of Monounsaturates are Olive Oil and Rapeseed oils.
2.Polyunsaturated Fatty Acids (PUFA)
Polyunsaturated fatty acids contain two or more double bonds in their chemical make up. They are least stable fatty acids to oxidation and as such are best used in cold applications. The most common source of polyunsaturates is Sunflowerseed oil
3.Trans Fatty Acids (TFA)
Trans fatty acids typically come from two sources, hydrogenated vegetable oils and animal fats. Recent scientific research suggests trans fats, although consumed in relatively small proportions, should be avoided due to their negative affect blood cholesterol levels.