The boiling points of vegetable oils are higher than water, so food is cooked at a higher temperature in oil. This means it cooks faster and also changes the flavor, colour and texture of the food. Some of the oil is absorbed and so energy content of the food increases.
Unsaturated oils can react with hydrogen so that some or all of the double carbon carbon bonds become single bonds. This is an additional reaction called hyrdogenation and is done at about 60 degrees using a nickel catalyst. Hydrogenation is used to increase the melting points of oil so they harden and become solid fats at room temperature.
Solid fats can be spread and can be used to make cakes, biscuits and pasteries.
REMEMBER: Oils are liquid at room temperature and fats are solids at room temperature.
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