Vegetable oils in food, fuel and emulsions and trans fats

Vegetable oils are important nutrients and provide a lot of energy. You must be careful not to eat excessive amounts to avoid becoming overweight.

Vegetable oils are also used as fuels for vehicles. Some of this biodiesel is made from waste cooking oil and rapeseed oil. Such fuels are carbon neutral, which means that they release only as much carbon dioxide when they burn as was used to make the original oil by photosynthesisphotosynthesis: The chemical change that occurs in the leaves of green plants. It uses light energy to convert carbon dioxide and water into glucose. Oxygen is produced as a by-product of photosynthesis.. This helps to reduce global warming. However, some people are concerned about whether it is ethical to use food crops in this way, instead of using them to feed hungry people.

Emulsions

Vegetable oils do not dissolve in water. If a mixture of oil and water is shaken, then left to stand, eventually a layer of oil will form on the surface of the water.

If an emulsifier is added to the oil and water, a mixture called an emulsion forms. Emulsions are more viscous than oil or water on their own, and contain tiny droplets of one of the liquids spread through the other liquid.

Examples of oil droplets in water:

• egg yolk
• milk
• ice cream
• salad cream
• mayonnaise

Examples of water droplets in oil:

• margarine
• butter
• skin cream
• moisturising lotion

Trans fats

Partially hydrogenated vegetable oils may contain trans fats. These are thought to cause health problems such as heart disease in humans, and food manufacturers are being encouraged to reduce the amount of them in our food.