Natural Fats and Oils L.O. I can explain the difference between saturated and unsaturated oils and fats and the risks associated with each.
What are plant oils? Plant oils are types of fat and can provide the body with energy. They are also good sources of vitamins. Oils can be made by crushing the seeds, beans and nuts of some plants, including olives and sunflowers. First the plant material is crushed to make a paste. The paste is then pressed to remove water and other impurities. Oils obtained in this way are often labelled “virgin” or “cold pressed”. Distillation and chemical processes can also be used to make plant oils. Oils obtained in this way are often labelled “refined”.
What are the differences between fats? Saturated fats contain no carbon-to-carbon double bonds. The straight fatty acids chains pack closely together. Unsaturated fats contain at least one carbon-to-carbon double bond. This bends the fatty acid chains and they cannot pack closely together. Saturated fats are less healthy than unsaturated fats because the dense packing makes them harder for the body to digest.
How is margarine made? Margarine was originally made using buttermilk, a waste product from making butter. Most modern margarines are made from plant oils. The oil is heated and hydrogen is pumped through it. This is called hydrogenation. Some of the carbon-to-carbon double bonds in the plant oils are broken and extra hydrogen atoms are added. This hardens the oil to make it a solid at room temperature. Not all the carbon-to-carbon double bonds are broken. This means that margarines still contain unsaturated fats. The oil is partially hydrogenated. Nickel is used as a catalyst for this reaction. It is filtered out before the margarine is packaged and sold.
What are trans fats? Trans fats are a type of fat that the body finds difficult to break down. These molecules can block the arteries of the heart. Trans fats can be formed by the partial hydrogenation of plant oils. Partially hydrogenated oils were used to make margarine. Today, most margarines are made using other methods and contain less trans fat. However, partially hydrogenated plant oils are commonly used in food products, such as biscuits and ready meals. Medical organisations in the UK have campaigned to get trans fats clearly labelled on food. Some supermarkets are now removing trans fats from their own-brand foods.
What are essential fatty acids? Essential fatty acids (EFAs) can be found in plant oils. They are needed by the body but it cannot produce them. Some research has shown that EFAs can help lower blood pressure and decrease the risk of blood clots. There are two main types of EFAs: • omega-3 – found in flax seeds (linseed), pumpkin seeds, walnuts and oily fish • omega-6 – found in corn, sunflower and soya oil It is easy to get enough omega-6 because corn and soya oil are often added to processed food. However, most people eat fewer foods containing omega-3.