Plant oils and their uses Flashcards
How are plant oils made?
Some fruits, seeds and nuts are rich in oils that are extracted by crushing them and then removing the oil by pressing it or sometimes distilling it. Water and other impurities, such as seed husks, are removed
What are vegetable oils useful for in terms of food?
They provide a lot of energy, and also contain nutrients
They have higher boiling points than water, so they cook foods (frying) at higher temperatures than by boiling. This cooks quicker and gives a the food different (usually better) flavour and texture, although it contains more energy when eaten
What is an emulsion?
What are examples of common emulsions?
A mixture of oil, an emulsifier, and another liquid that has a thicker (more viscous) and creamier texture than both oil and water. This texture gives them a better appearance, and makes them sticky and so suitable for coating (cosmetics, paint) Salad dressing (vinegar, olive oil and mustard [the emulsifier]), ice cream, cosmetics and paint
Describe the structure of an emulsifier
They have a hydrophilic ‘head’ that dissolves in water but not in oil, and a hydrophilic ‘tail’ that dissolves in oil but not in water. This means they can join oil and water together
What does the bromine water test show?
It goes colourless if there is a double carbon-carbon bond or an unsaturated oil present
Vegetable oils are unsaturated
How and why are unsaturated vegetable oils hardened?
Reacting them with hydrogen at about 60ºC under the presence of a nickel catalyst. The hydrogen adds to the carbon-carbon double bond, and gives the oils higher melting points, which makes them solid at room temperature. This means they are useful as spreads and in cakes and pastries
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